Gallons to Cubic Feet Converter: US Water, Pool, and Tank Volume Calculations
Convert US gallons to cubic feet using the exact legal definition: 1 US gallon = 231 cubic inches = 231/1728 ft³. Includes water utility CCF billing reference, pool sizing, water heater presets, water weight output, and free PDF export.
Gallons to Cubic Feet Calculator
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1 US gallon = 231 cubic inches (exact US legal definition). 1 ft³ = 1728 in³ = 7.48052 gallons.
US Volume Reference Comparison (Gallons)
What Is a US Gallon: The 231 Cubic Inch Legal Definition Every American Should Know
The US liquid gallon is defined by federal law as exactly 231 cubic inches. This definition has been in place since the Weights and Measures Act of 1832 codified the “wine gallon” as the standard US liquid gallon, fixing it at 231 cubic inches based on a Queen Anne-era standard from 1707. One cubic inch is the volume of a cube one inch on each side. One cubic foot is the volume of a cube one foot (12 inches) on each side, so it equals 12 times 12 times 12 equals 1,728 cubic inches. Dividing 231 by 1,728 gives the exact cubic feet per gallon: 231/1728, which simplifies to the fraction 77/576, a repeating decimal of 0.133680555… (with the 5 repeating). This conversion is exact, not an approximation.
One cubic foot contains 1,728 divided by 231 equals 576/77 equals 7.480519480… US gallons (the 480519 block repeats). This recurring decimal is why you will see values like 7.48, 7.481, or 7.4805 as approximations in plumbing, construction, and HVAC references. All are rounded versions of the exact 576/77 ratio. This calculator computes at full Big.js precision so your results match what engineering handbooks and NIST tables show at any decimal depth you need.
Important: the US gallon (231 in³, 3.785 L) is not the same as the Imperial gallon used in the United Kingdom, Canada (historically), and some other countries. One Imperial gallon equals exactly 4.54609 liters, which is about 20% larger than the US gallon. A recipe or product labeled in “gallons” from a UK source uses the larger Imperial gallon. This calculator uses US liquid gallons exclusively.
Why US Water Utilities Bill in Cubic Feet Instead of Gallons
Most American homeowners receive a water utility bill measured in CCF (hundred cubic feet), with 1 CCF equaling 100 cubic feet. At 7.48052 gallons per cubic foot, 1 CCF equals 748.052 gallons. Some utilities bill in MCF (thousand cubic feet), where 1 MCF equals 7,480.52 gallons. A few utilities bill directly in gallons (particularly in the Southwest where water scarcity makes per-gallon pricing more practical).
The reason cubic feet dominate US water metering is historical: the original nutating disk and positive displacement water meters used in American homes from the late 19th century onward were calibrated in cubic feet because that was the standard unit for gas and water utility measurement. Replacing the entire installed base of meters to display gallons would have cost billions of dollars and offered no practical benefit to utilities, so the cubic foot stuck. The American Water Works Association (AWWA) publishes annual water use benchmarks in both gallons per day and cubic feet per month, and knowing how to convert between them is essential for reading your bill, comparing usage across households, and understanding efficiency targets.
How This Gallons to Cubic Feet Converter Works
Enter a volume in US gallons and the calculator instantly returns cubic feet (using the exact 231/1728 ratio), liters (using the exact 3.785411784 L per gallon value derived from the 2.54 cm per inch definition), milliliters, and cubic inches. The reverse direction converts cubic feet to gallons using the exact 1728/231 ratio. The context panel below results shows the water weight in pounds at 68 degrees Fahrenheit (8.3454 lb per US gallon at standard conditions), along with a comparison to familiar US volume references like water heaters, aquariums, and pool sizes.
The batch mode accepts up to 20 values and outputs a table with cubic feet, gallons, liters, and water weight for each. This is particularly useful for plumbing contractors calculating pipe fill volumes, pool service technicians comparing chemical dosing for multiple pools, or homeowners comparing water heater capacities. The logarithmic comparison chart displays your input against common US volume references on a scale from 1 gallon to 18,000 gallons, making it easy to see how your value relates to everyday containers and installations.
US Swimming Pool, Water Heater, and Aquarium Sizing in Gallons and Cubic Feet
Some of the most common reasons Americans convert gallons to cubic feet involve home and commercial installations. Here are the standard US volume references every homeowner, plumber, and pool professional needs to know.
Residential Water Heaters
US residential water heaters are sold in gallon capacities. The most common tank sizes are 30, 40, 50, 75, and 80 gallons. To understand the physical space a water heater tank occupies:
- 30-gallon tank: 30 times 0.133681 equals 4.010 cubic feet. Typical dimensions: about 18 inches diameter by 4 feet tall.
- 40-gallon tank: 40 times 0.133681 equals 5.347 cubic feet. Standard size for a household of 2 to 3 people.
- 50-gallon tank: 50 times 0.133681 equals 6.684 cubic feet. Standard for households of 3 to 5 people.
- 80-gallon tank: 80 times 0.133681 equals 10.694 cubic feet. Commercial and high-demand residential applications.
These cubic foot values matter when planning utility room space, calculating whether a tankless heater installation saves meaningful square footage, or specifying replacement units in a mechanical room layout. The US Department of Energy also uses gallons as the standard for water heater capacity in its consumer guides and energy efficiency ratings (Energy Factor and Uniform Energy Factor specifications).
Swimming Pools and Hot Tubs
US pool contractors size pools in gallons for chemical treatment calculations and in cubic feet (or cubic yards) for excavation and concrete pour estimates. A standard rectangular residential pool 15 feet wide by 30 feet long with an average depth of 5 feet contains 15 times 30 times 5 equals 2,250 cubic feet of water. Converting to gallons: 2,250 times 7.48052 equals 16,831 US gallons. The commonly cited average US residential pool of 18,000 gallons corresponds to 18,000 times 0.133681 equals 2,406.25 cubic feet of water. Chemical treatment rates (chlorine, pH adjusters, algaecides) are always calculated per 10,000 gallons, so pool professionals constantly need to convert their pool’s cubic footage to gallons and vice versa.
Fish Tanks and Aquariums
Aquarium sizes in the US are sold and described in gallons. The physical footprint and water volume in cubic feet help hobbyists calculate load-bearing requirements for tank stands, floor support, and cabinetry. Common sizes: a 10-gallon tank equals 1.337 cubic feet (78 lbs of water). A 55-gallon tank equals 7.352 cubic feet (459 lbs). A 125-gallon tank equals 16.710 cubic feet (1,043 lbs). Water weighs approximately 8.3454 pounds per US gallon at 68 degrees Fahrenheit, so a full 75-gallon reef aquarium with rock and sand can weigh 1,200 lbs or more. Floor joist load ratings in residential construction run 40 to 50 pounds per square foot, so a 125-gallon aquarium occupying 4 square feet of floor must be positioned over a structural beam.
Three Real US Gallon-to-Cubic-Foot Conversion Examples
Reading Your Water Utility Bill: Converting CCF to Gallons
A homeowner in Phoenix, Arizona receives a water bill showing usage of 4 CCF for the month. Their water rate is $3.20 per CCF and they also have a tiered sewer charge based on monthly gallon usage. They need to convert the CCF water usage to gallons to determine their sewer tier and to compare their usage with the AWWA national average of about 80 gallons per person per day.
4 CCF equals 400 cubic feet. Converting to gallons: 400 times 7.480519480… equals 2,992.208 gallons for the month. A 30-day billing cycle means daily usage of 2,992.208 divided by 30 equals 99.7 gallons per day. For a two-person household, that is 49.9 gallons per person per day, well below the 80-gallon national average. For Phoenix’s sewer rate structure, a monthly usage of 2,992 gallons falls in the base tier (under 4,000 gallons) and qualifies for the lower sewer charge rate.
Swimming Pool Fill Volume and Chemical Treatment Budget
A pool contractor in Florida is filling a new gunite pool that is 18 feet wide by 36 feet long with a shallow end of 3.5 feet and a deep end of 8 feet. The average depth is (3.5 plus 8) divided by 2 equals 5.75 feet. The contractor needs to calculate the pool volume in both cubic feet (for structural and engineering specs) and gallons (for chemical treatment and utility connection sizing).
Volume in cubic feet: 18 times 36 times 5.75 equals 3,726 cubic feet. Converting to gallons: 3,726 times 7.480519480… equals 27,872.7 US gallons. Initial chlorine shock treatment at 1 pound of 73% calcium hypochlorite per 10,000 gallons requires 27,872.7 divided by 10,000 equals 2.787 rounds to 2.8 pounds of shock. The pool will require approximately 2 days to fill using a standard 3/4-inch garden hose at 10 gallons per minute (27,873 gallons divided by 10 GPM = 2,787 minutes = 46.5 hours).
Rainwater Harvesting Tank Sizing for a Texas Ranch
A property owner in the Texas Hill Country wants to install a rainwater harvesting system. Their roof catchment area is 2,000 square feet and their region averages 32 inches of rainfall per year. They want to know how large a storage tank they need in both gallons and cubic feet, and how the tank dimensions translate to a standard round poly tank selection.
Annual roof harvest: 2,000 sq ft times (32/12) ft of rain = 2,000 times 2.667 = 5,333 cubic feet of water per year. Converting to gallons: 5,333 times 7.48052 = 39,896 gallons per year. For 60 days of reserve (the dry-season buffer recommended by the Texas A&M AgriLife Extension), they need 39,896 times (60/365) = 6,561 gallons reserve capacity. A standard 5,000-gallon round poly tank (5,000 times 0.133681 = 668.4 cubic feet) plus a second 2,500-gallon tank gives 7,500 gallons reserve, covering the 6,561-gallon target with margin. Combined tank footprint: two 8-foot-diameter tanks at about 7 feet tall each.
Four Expert Tips for Working with Gallons and Cubic Feet in US Home and Commercial Projects
Memorize 7.48: The Cubic Foot to Gallon Shortcut
The most useful single number in US plumbing and water system design is 7.48: one cubic foot holds approximately 7.48 US gallons (exact: 7.480519480…). Plumbers, irrigation engineers, pool contractors, and civil engineers use this number constantly. To find how many gallons fit in a tank or pipe, calculate the cubic foot volume (length times width times height for rectangular, pi times r squared times height for cylindrical) and multiply by 7.48. For a 6-inch diameter pipe (0.5-foot diameter, 0.25-foot radius) that is 100 feet long: volume = 3.14159 times 0.0625 times 100 equals 19.635 cubic feet times 7.48 equals 146.9 gallons of water in that pipe section. At 8.34 lbs per gallon, that pipe holds 1,224 lbs of water when full.
Water Weighs 8.34 Pounds Per US Gallon at Room Temperature
Water at 68 degrees Fahrenheit (20 degrees Celsius) has a density of approximately 0.99821 g/mL, which translates to 8.3390 lbs per US gallon. At the often-cited 62 degrees Fahrenheit (maximum density temperature for fresh water is actually near 39 degrees F), it is 8.3454 lbs per gallon. For practical planning purposes, 8.34 lbs per gallon is accurate to better than 0.2% for most temperature ranges you encounter in home water systems. A full 55-gallon drum of water weighs 55 times 8.34 equals 458.7 lbs, not counting the drum itself. An 18,000-gallon swimming pool full of water holds 18,000 times 8.34 equals 150,120 lbs of water, or about 75 tons. Structural engineers designing pool decks and mechanical rooms size beams and footings around these water load numbers.
Pool Volume Formula: Length x Width x Average Depth x 7.48 = Gallons
For any rectangular pool with a sloped bottom, the standard US pool volume formula is: length in feet times width in feet times average depth in feet times 7.48052 gallons per cubic foot equals total gallons. Average depth equals (shallow end depth plus deep end depth) divided by 2, which works for linearly sloped bottoms. For pools with a level shallow end and a level deep end connected by a slope transition, calculate each section separately. Round and oval pools use: diameter in feet squared times 0.7854 (pi/4) times average depth times 7.48. Knowing your pool’s gallon volume is essential for chemical calculations (all pool chemical dosing is per 10,000 gallons), for accurate water loss monitoring, and for calculating pump turnover time (gallons divided by pump flow rate in GPH).
Flow Rates: Convert GPM and GPH to Cubic Feet per Minute or Hour
Plumbing and HVAC specifications often use both gallons per minute (GPM) and cubic feet per minute (CFM) or cubic feet per hour (CFH) for flow rates, and the two sets of units appear side by side in equipment specs. To convert GPM to CFM, divide by 7.48052: a 15 GPM well pump moves 15 divided by 7.48052 equals 2.004 cubic feet per minute. To convert GPH to CFH, divide by 7.48052: a 2,400 GPH irrigation pump moves 2,400 divided by 7.48052 equals 320.8 cubic feet per hour. Conversely, a 5 CFM industrial water pump moves 5 times 7.48052 equals 37.4 GPM. Flow rate conversions between gallons and cubic feet use exactly the same 7.48052 factor as volume conversions because the time dimension cancels: if 1 ft³ = 7.48052 gallons, then 1 ft³/min = 7.48052 gallons/min.
Gallon and Cubic Foot Relationships Across US Industry Sectors
The gallon-to-cubic-foot conversion shows up in a surprising range of American industries, often in ways that are invisible to consumers but critical to the engineers and operators who manage those systems. Here is how the conversion plays out across several major US sectors where both units coexist.
Oil and Gas: Barrels, Cubic Feet, and Gallons
The US petroleum industry uses a unique mix of volume units that can be disorienting. Crude oil is measured and traded in barrels, where one US oil barrel equals 42 US gallons. Converting that to cubic feet: 42 times 0.133680555 equals 5.615 cubic feet per barrel. Natural gas, on the other hand, is measured in cubic feet at standard conditions (60 degrees Fahrenheit and 14.73 psia), with large volumes expressed in Mcf (thousand cubic feet), MMcf (million cubic feet), or Bcf (billion cubic feet). A producing oil well might yield 100 barrels per day of crude oil (421 gallons, 56.15 cubic feet as liquid) and 50 Mcf per day of associated natural gas (50,000 cubic feet as gas). These two streams are measured in completely different unit frameworks, but both ultimately connect back to gallons and cubic feet as the base units. The US Energy Information Administration reports all petroleum and natural gas production statistics using this hybrid unit system.
Fire Protection Engineering: Gallons per Minute and Water Supply
US fire protection engineering specifies water supply requirements in gallons per minute (GPM) and tank or reservoir sizes in gallons. The National Fire Protection Association’s NFPA 22 standard governs water storage tanks for fire protection and specifies tank capacities from 1,500 gallons (200.6 cubic feet) for residential sprinkler systems to 500,000 gallons (66,840 cubic feet) for large industrial fire suppression reserves. Fire hydrant flow rates are tested in GPM: a fire hydrant that flows at 1,000 GPM at 20 psi residual pressure must draw from a water main that can sustain that flow rate. For storage tank sizing, fire protection engineers convert the GPM demand times the required fire flow duration in minutes to get total gallons needed, then convert to cubic feet for structural design. A 2-hour fire flow requirement at 1,500 GPM needs 180,000 gallons = 24,065 cubic feet of stored water.
Irrigation and Agriculture: Acre-Inches and Flow Volumes
US agricultural irrigation uses yet another unit: the acre-inch, which is the volume of water needed to cover 1 acre to a depth of 1 inch. One acre-inch equals 43,560 square feet times (1/12) foot equals 3,630 cubic feet, which equals 3,630 times 7.48052 equals 27,154 US gallons. US corn production typically requires 15 to 25 acre-inches of water per growing season; in gallons, that is 407,000 to 679,000 gallons per acre. The conversion between irrigation flow rates (gallons per minute or cubic feet per second) and seasonal water volume (acre-feet or acre-inches) is fundamental to water rights administration in western states, where the Colorado, Rio Grande, and Sacramento river systems allocate water in exactly these terms.
Aquaculture and Fish Hatcheries: Oxygen, Flow, and Tank Volume
Commercial fish hatcheries and aquaculture facilities in the US calculate oxygen demand and water exchange requirements based on tank volume in gallons, while water treatment infrastructure is typically designed in cubic feet and gallons per minute. A 5,000-gallon circular tank holding rainbow trout at a density of 0.25 lbs per gallon (1,250 lbs of fish) requires approximately 5 liters of oxygen per minute to maintain DO (dissolved oxygen) above 7 mg/L. The water exchange rate to carry away waste is typically 10 to 20 tank volumes per day, meaning 50,000 to 100,000 gallons per day flow through a 5,000-gallon tank. At 100,000 gallons per day divided by 1,440 minutes per day equals 69.4 GPM, which equals 69.4 divided by 7.48052 equals 9.28 cubic feet per minute of water flow through the system. Aquaculture engineers do this gallon-to-CFM conversion daily when sizing pumps, aeration systems, and settling chambers.
Quick Reference: US Gallons to Cubic Feet Conversion Table
| US Gallons | Cubic Feet | Liters | Cubic Inches | US Context |
|---|---|---|---|---|
| 1 gal | 0.13368 | 3.785 | 231 | Baseline US gallon |
| 5 gal | 0.66840 | 18.927 | 1,155 | Camping water jug |
| 10 gal | 1.33681 | 37.854 | 2,310 | Small aquarium |
| 20 gal | 2.67361 | 75.708 | 4,620 | Standard aquarium |
| 40 gal | 5.34722 | 151.416 | 9,240 | Standard water heater |
| 55 gal | 7.35243 | 208.197 | 12,705 | 55-gallon storage drum |
| 100 gal | 13.3681 | 378.541 | 23,100 | Large storage tank |
| 748.052 gal | 100.000 | 2,831.7 | 172,800 | 1 CCF (water utility billing) |
| 1,000 gal | 133.681 | 3,785.4 | 231,000 | Cistern / residential billing ref |
| 10,000 gal | 1,336.81 | 37,854 | 2,310,000 | Small residential pool |
| 18,000 gal | 2,406.25 | 68,137 | 4,158,000 | Average US residential pool |
| 7.48052 gal | 1.00000 | 28.317 | 1,728 | 1 cubic foot reference |
Frequently Asked Questions About Gallons and Cubic Feet
One US gallon equals 231/1728 cubic feet, which equals 77/576 cubic feet, which equals the repeating decimal 0.133680555… cubic feet. This comes from the legal definition: 1 US gallon = 231 cubic inches exactly, and 1 cubic foot = 12 cubed = 1728 cubic inches exactly. So the conversion is 231 divided by 1728, which simplifies to the fraction 77/576. The commonly used approximations are 0.1337 or 0.134 cubic feet per gallon. This calculator uses the full exact precision.
One cubic foot contains 1728/231 = 576/77 = 7.480519480… US gallons. The 7.48 shortcut is accurate enough for most plumbing and pool calculations. Plumbers, pool contractors, and civil engineers all use 7.48 gallons per cubic foot as a working constant. For precise water billing analysis or tank capacity calculations, use the full value 7.480519480… (the pattern 480519 repeats). This calculator computes using Big.js arithmetic to avoid any rounding errors at this stage of the calculation.
CCF stands for “hundred cubic feet” and equals 100 cubic feet of water, which equals 748.052 US gallons. US water utilities historically measured in cubic feet because the early water meters installed in the late 19th and early 20th centuries were calibrated in cubic feet. Replacing all meters to display gallons was never done because it offered no practical benefit to the utility. To convert your bill from CCF to gallons, multiply CCF by 748.052. Example: 6 CCF equals 6 times 748.052 equals 4,488 gallons used that month. Some utilities in the Southwest (California, Arizona, Nevada) are switching to gallon-based billing as part of conservation communication efforts, but cubic feet meters remain dominant in most US cities.
For a rectangular pool: multiply length times width times average depth (all in feet) to get cubic feet, then multiply by 7.48 to get gallons. Average depth = (shallow end depth + deep end depth) / 2 for a linearly sloped pool. Example: 16 ft x 32 ft pool with 3.5 ft shallow end and 7 ft deep end. Average depth = (3.5 + 7) / 2 = 5.25 ft. Volume = 16 x 32 x 5.25 = 2,688 cubic feet x 7.48052 = 20,105 gallons. For a round pool: pi (3.14159) x radius squared x average depth x 7.48. For irregular shapes, break the pool into rectangular and circular sections and sum their volumes. Pool chemical treatment (chlorine, pH adjusters) is always calculated per 10,000 gallons, so an accurate gallon count is essential.
A 55-gallon drum (a standard US industrial storage drum) holds 55 times 0.133680555… equals 7.352430… cubic feet of liquid. In other units: 55 gallons equals 55 times 231 equals 12,705 cubic inches, or 55 times 3.785411784 equals 208.197 liters. A standard 55-gallon steel drum weighs about 40 to 50 lbs empty and about 40 plus 55 times 8.34 equals 498.7 lbs when filled with water. With heavier liquids (used motor oil is about 7.5 lbs per gallon), the filled weight would be 40 plus 55 times 7.5 equals 452.5 lbs. The 55-gallon drum size is widely used in US industrial storage, agriculture, and emergency water preparedness planning.
A 40-gallon water heater tank holds 40 times 0.133680555… equals 5.347222… cubic feet of water. The tank itself physically occupies more space than this because of the tank walls, insulation, and connections: a typical 40-gallon tank is about 18 to 20 inches in diameter and 54 to 58 inches tall, occupying roughly 8 to 9 cubic feet of floor-to-ceiling space. A 50-gallon tank holds 50 times 0.133681 equals 6.684 cubic feet of water and is about 20 to 22 inches in diameter and 54 to 58 inches tall. Tankless water heaters eliminate the water volume entirely but require a larger gas supply line or electrical service upgrade to heat water on demand.
No. The US liquid gallon is 231 cubic inches = 3.785411784 liters. The Imperial (UK) gallon is 277.42 cubic inches = 4.54609 liters exactly. The Imperial gallon is about 20% larger than the US gallon. This matters in several practical contexts: a US 5-gallon gas can holds 18.93 liters, while a UK “5-gallon” container holds 22.73 liters. Old Canadian recipes may reference Imperial gallons. Fuel consumption (miles per gallon) is significantly different depending on which gallon is used: a car rated at 40 mpg in the UK achieves about 33.3 mpg on the US scale using the same fuel consumption, because UK mpg uses the larger Imperial gallon. This calculator uses US liquid gallons only.
The US Environmental Protection Agency (EPA) estimates that the average American family uses about 300 gallons per day, or approximately 9,000 gallons per month. In cubic feet, that is 9,000 divided by 7.48052 equals 1,203 cubic feet per month, or about 12 CCF. The EPA WaterSense program targets efficient household water use of about 70 gallons per person per day, which for a family of four is 280 gallons per day or about 8,400 gallons per month. Water-efficient households using high-efficiency fixtures can reduce this to 50 to 60 gallons per person per day. Indoor use accounts for about 70% of residential water use, with toilets (24%), showers (20%), and faucets (19%) as the top categories.
Calculate the pipe’s volume in cubic feet using: pi times (inside radius in feet) squared times length in feet. Then multiply by 7.48052 to get gallons. For common pipe sizes (nominal inside diameter in inches): 1-inch pipe (0.0417 ft radius) per 100 feet = pi times 0.001736 times 100 = 0.545 cubic feet = 4.08 gallons. 2-inch pipe per 100 feet = pi times 0.00694 times 100 = 2.18 cubic feet = 16.32 gallons. 4-inch pipe per 100 feet = pi times 0.02778 times 100 = 8.73 cubic feet = 65.3 gallons. 6-inch pipe per 100 feet = pi times 0.0625 times 100 = 19.63 cubic feet = 146.9 gallons. These values matter for flushing new mains, calculating chlorination treatment volumes, and designing pressure-maintenance systems.
One acre-foot of water equals the volume needed to cover 1 acre of land to a depth of 1 foot. One acre equals 43,560 square feet, so 1 acre-foot equals 43,560 cubic feet. Converting to gallons: 43,560 times 7.480519… equals 325,851 US gallons. Acre-feet are the standard water volume unit for agricultural water rights, reservoir capacity, and large-scale irrigation systems in the Western United States. The Colorado River Compact, which governs water rights for the entire Colorado River basin (serving over 40 million people across seven states), allocates water in millions of acre-feet per year. One million acre-feet equals 325.851 billion gallons or 43.56 billion cubic feet.
One cubic foot per second (CFS or cfs) equals 1728/231 times 60 equals 448.831 gallons per minute (GPM). The cubic foot per second is the standard flow rate unit for rivers, streams, and large irrigation channels in US water resource engineering. A flow of 1 cfs is often called a “miner’s inch” in older Western water rights documentation. Large municipal water treatment plants are rated in MGD (million gallons per day) or CFS: 1 MGD equals 1,000,000 divided by 1,440 minutes equals 694.4 GPM equals 694.4 divided by 448.831 equals 1.547 CFS. Small residential well pumps typically produce 5 to 25 GPM, while municipal fire hydrants flow at 500 to 1,500 GPM depending on local water main sizing.
One cubic foot equals 28.316846592 liters exactly. This exact value comes from: 1 ft cubed = 1728 cubic inches, and 1 cubic inch = (2.54 cm)^3 = 16.387064 mL, so 1 ft cubed = 1728 times 16.387064 mL = 28,316.846592 mL = 28.316846592 liters. To convert cubic feet to liters, multiply by 28.3168. Examples: 5 ft cubed = 141.584 liters. 100 ft cubed (1 CCF) = 2,831.685 liters. 1,000 ft cubed = 28,316.847 liters. For water utility context: 1 CCF of water equals 2,831.685 liters, which is roughly 2,832 one-liter water bottles.
One US liquid gallon equals exactly 3,785.411784 milliliters (mL). This exact value is derived from: 1 US gallon = 231 cubic inches, 1 cubic inch = (2.54 cm)^3 = 16.387064 cm^3 = 16.387064 mL, so 1 gallon = 231 times 16.387064 = 3,785.411784 mL = 3.785411784 liters. For practical conversions: 1 gallon = about 3.785 liters, or roughly 3 and 3/4 liters. One gallon of water weighs about 8.34 pounds at 68 degrees Fahrenheit. Common packaging sizes: a 1-gallon jug of water (3,785 mL) is slightly less than a 4-liter container. A 2-liter soda bottle is about 0.528 gallons.
10,000 US gallons equals 10,000 times 0.133680555… equals 1,336.806 cubic feet. That volume of water weighs 10,000 times 8.34 pounds equals 83,400 pounds, or about 41.7 tons. A 10,000-gallon above-ground tank with a round footprint of 10 feet in diameter has a floor area of about 78.5 square feet. At 1,336.8 cubic feet divided by 78.5 square feet, it would stand about 17 feet tall, which is why large tanks have larger footprints: a 12-foot diameter tank has 113 square feet of floor area and stands about 11.8 feet tall to hold 10,000 gallons. Underground cisterns can be sized differently because they distribute load to surrounding soil rather than a structural floor.
The exact formula is: cubic feet = gallons times (231/1728). Since 1 US gallon = 231 cubic inches exactly, and 1 cubic foot = 12 cubed = 1728 cubic inches exactly, the ratio is 231/1728 = 77/576 = 0.133680555… (repeating 5). The reverse: gallons = cubic feet times (1728/231) = cubic feet times (576/77) = cubic feet times 7.480519480… (repeating 480519). Both fractions are exact and rational, meaning no information is lost in the conversion: if you convert gallons to cubic feet and then back to gallons using these exact fractions, you return to exactly the original value. The approximations 0.1337 and 7.48 used in field calculations introduce less than 0.005% error, acceptable for most construction and plumbing estimates.
Yes. This tool is completely free with no account required, no ads, and no data sent to any server. All calculations run locally in your browser using Big.js arbitrary-precision arithmetic with the exact NIST-defined conversion factor: 1 US gallon = 231 cubic inches exactly. Results are accurate to the precision of your input with no floating-point rounding errors. The batch mode handles up to 20 values simultaneously, and the PDF export generates a formatted report including a reference table of common US volume benchmarks. Use the context panel to see water weight output in pounds for any volume you enter.
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Legal Disclaimer and Editorial Transparency
This gallons to cubic feet converter is provided for educational and general informational purposes only. All conversions use the exact US legal definition: 1 US liquid gallon = 231 cubic inches exactly (US Weights and Measures Acts; NIST SP 811), and 1 cubic foot = 1728 cubic inches exactly. Liter equivalents are derived from the exact definition 1 inch = 2.54 centimeters (International Yard and Pound Agreement, 1959). Water weight estimates use a density of approximately 8.3454 lbs per US gallon at 68 degrees Fahrenheit and are approximate at other temperatures. Pool volume formulas are standard engineering estimates for rectangular and oval pools; irregularly shaped pools require professional measurement. Water utility billing unit (CCF) and rate information should be verified with your local water authority. This tool is not a substitute for professional plumbing, engineering, or water management consultation. Content written and reviewed by the USCalculators.com editorial team.