💧 1 Cu Ft = 7.480519… US Gal (1728/231, Exact Repeating)

Cubic Feet to Gallons Converter: Pool Volume Formula, Aquarium Nominal vs Actual Gallons, Rainwater Harvesting Calculations, and Why a 55-Gallon Tank Holds 56.73 Gallons

Built and reviewed by David (MBA Finance) · Updated August 2026

1 cubic foot = 1728/231 = 7.480519480519… US liquid gallons (exact repeating decimal; 576/77 fraction). Pool: L x W x avg depth (ft) x 7.48052. Rainwater: sq ft x inches / 12 x 7.48052. 55-gal aquarium = 56.73 actual gal. 27 cu ft = 1 cu yd = 201.97 gal. 1 cu ft water = 62.37 lb. Four App Decoder modes: pool and spa, aquarium, rainwater, HVAC and water heaters. 16 presets. Free PDF. WhatsApp share.

1 cu ft = 7.48052 US gal (exact) Pool: L x W x depth x 7.48 55-gal tank = 56.73 actual gal 1 in rain x 1,000 sq ft = 623 gal 27 cu ft = 1 cu yd = 201.97 gal Batch up to 20 Values

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Cu Ft to US Gallons

Cubic Feet

cu ft

Common Presets

1 cu ft = 7.48052 US gal (exact: 1728/231). Pool: L x W x depth(ft) x 7.48052. Aquarium: cu in / 231. Rainwater: sq ft x in / 12 x 7.48052. 27 cu ft = 201.97 gal (1 cu yd). 1 cu ft water = 62.37 lb. Aquarium labels are nominal: 55-gal label = 56.73 actual gal.

Conversion Result

0 US gallons

0Liters

0Cu Inches

0Water Wt (lb)

Formula and Reference

Why 1 Cubic Foot = 7.480519… US Gallons: The Queen Anne Wine Gallon, 231 Cubic Inches, and the Exact Repeating Decimal

The conversion 1 cubic foot = 7.48051948051948… US gallons follows directly from two exact definitions. First: 1 US liquid gallon = 231 cubic inches, a definition that traces to the British Queen Anne wine gallon of 1707 (a standard wine barrel size), codified into US law and confirmed by NIST. Second: 1 cubic foot = 12 x 12 x 12 = 1,728 cubic inches exactly. Dividing: 1,728 / 231 = 576/77 = 7.480519480519… (the digit sequence 480519 repeats infinitely). This is not an approximation; the fraction 576/77 is exact. Using 7.5 gallons per cubic foot instead introduces a 0.26% error, which on a 25,000-gallon pool produces a 65-gallon overcount, meaning your pool chemical dosing calculations are off by 65 gallons at every cycle.

Water volume, weight, and pressure are related through this conversion. 1 cubic foot of pure water at 68 degrees Fahrenheit (20 degrees Celsius) weighs 62.3701958 pounds = 62.37 lb. Since 1 cubic foot = 7.48052 US gallons and 1 US gallon of water = 8.34 lb at 68 degrees F: 7.48052 x 8.34 = 62.37 lb per cubic foot (the two approaches agree). For structural calculations: 1 cubic foot of water = 62.37 lb = 0.031 US tons. A 20,000-gallon pool holds approximately 167,000 lb = 83.5 US tons of water. For deck load: 1 cubic foot of water over 1 square foot = 62.37 lb per square foot (psf) of distributed load. NIST at NIST.gov. NIST Handbook 44 at NIST.gov/pml. USGS water properties at USGS.gov.

1 cu ft = 7.48052 US gal Exact: 1728/231 = 576/77. “480519” repeats. 1 cu ft = 1,728 cu in = 28.317 L. 1 gal = 231 cu in (US law). NIST Handbook 44.

55-gal tank = 56.73 actual gal 48x13x21 in = 13,104 cu in / 231 = 56.71 US gal. Aquarium labels are nominal; actual volume is usually more. Use actual for chemical dosing.

1 in rain x 1,000 sq ft = 623 gal 1 in / 12 = 0.0833 cu ft per sq ft. x 1,000 sq ft = 83.33 cu ft x 7.48052 = 623.4 gal. Rainwater harvesting base formula.

How This Four-Mode Cubic Feet to Gallons Converter Serves Pool Builders, Aquarists, Rainwater Engineers, and HVAC Technicians

Mode 1: Single Cubic Feet to US Gallons

Enter any cubic foot value. Output: US gallons (exact fraction 576/77), liters, cubic inches, cubic yards, and water weight in pounds at 68 degrees F. 16 presets from 0.134 cu ft (1 US gallon) through 100 cu ft. The context note decodes each value: HVAC condensate range, aquarium tank sizes (nominal vs actual), water heater capacities, pool fractions, and rainwater volumes. Bar chart compares your input to reference sizes.

Mode 2: App Decoder

Pool and Spa Volume (common residential pools from 320 cu ft spa to 4,400 cu ft estate pool with chlorine shock reference), Aquarium: Nominal vs Actual Gallons (six standard tank sizes showing the discrepancy between nominal label and actual cubic-foot volume), Rainwater Harvesting Calculations (roof areas from 100 sq ft to 1,000 cu ft basis), and HVAC and Water Heater Capacities (30-gal through 80-gal water heaters plus condensate estimates).

Mode 3: Batch Cubic Feet to Gallons

Enter up to 20 cubic foot values. Output: a table with US gallons, liters, cubic inches, and water weight in pounds for each. Useful for a pool contractor tabulating multiple pool designs, an aquarist comparing custom tank dimensions, or a civil engineer calculating cistern and collection volumes.

Complete Cubic Feet to Gallons Reference: Aquarium Actual vs Label, Water Heater Sizes, Pool Volumes, and the 231 Cubic Inch Gallon Definition

Cubic Feet	US Gallons	Liters	Cu Inches	Water Weight (lb)	Common Reference
0.134	1.002 gal	3.791 L	231.6 cu in	8.35 lb	Approximately 1 US gallon. HVAC: drain pan unit size.
1.000	7.481 gal	28.317 L	1,728 cu in	62.37 lb	Basic unit. 1 in rain x 12 sq ft = 1 cu ft = 7.481 gal.
1.389	10.39 gal	39.31 L	2,400 cu in	86.22 lb	Nominal “10-gal” aquarium (20x10x12 in). Actual: 10.39 gal.
2.500	18.70 gal	70.79 L	4,320 cu in	155.3 lb	Nominal “20-gal long” (30x12x12 in). Actual: 18.70 gal.
3.750	28.05 gal	106.19 L	6,480 cu in	232.9 lb	Nominal “29-gal” (30x12x18 in). Actual: 28.05 gal.
4.008	29.99 gal	113.55 L	6,926 cu in	249.0 lb	30-gallon water heater capacity. Suitable for 1-2 persons.
5.344	39.98 gal	151.40 L	9,234 cu in	332.0 lb	40-gallon water heater. Most common US residential size.
6.000	44.88 gal	170.10 L	10,368 cu in	372.6 lb	Nominal “40-gal breeder” (36x18x16 in). Actual: 44.88 gal (not 40).
6.680	49.99 gal	189.22 L	11,543 cu in	415.0 lb	50-gallon water heater. Suitable for 3-4 persons.
7.583	56.73 gal	214.76 L	13,104 cu in	471.1 lb	Nominal “55-gal” aquarium (48x13x21 in). Actual: 56.73 gal (not 55).
10.500	78.55 gal	297.33 L	18,144 cu in	652.3 lb	Nominal “75-gal” aquarium (48x18x21 in). Actual: 78.55 gal (not 75).
10.688	79.96 gal	302.65 L	18,468 cu in	663.9 lb	80-gallon commercial water heater. 5+ persons or high-demand use.
27.000	201.97 gal	764.55 L	46,656 cu in	1,677 lb	1 cubic yard = 27 cu ft = 201.97 US gal. Concrete, bulk material reference.
1 (ref)	7.48051948… gal	28.317 L	1,728 cu in	62.37 lb	Exact: 1728/231 = 576/77 US gal. Source: NIST Handbook 44.

Exact: 1 cu ft = 1728/231 = 576/77 = 7.480519480519… US gal (480519 repeats). Source: NIST.gov. Water density at 68 F: 62.3701958 lb/cu ft (USGS). Pool formula: CDC.gov/healthywater. Rainwater: EPA.gov/watersense. HVAC: Energy.gov.

Aquarium Tank Nominal Labels vs Actual Cubic Feet and Gallons

Nominal Label	Actual Dimensions	Cubic Inches	Cubic Feet	Actual US Gallons	Gap (gal)
“10 gal”	20 x 10 x 12 in	2,400 cu in	1.389 cu ft	10.39 gal	+0.39 gal
“20 gal long”	30 x 12 x 12 in	4,320 cu in	2.500 cu ft	18.70 gal	-1.30 gal
“29 gal”	30 x 12 x 18 in	6,480 cu in	3.750 cu ft	28.05 gal	-0.95 gal
“40 gal breeder”	36 x 18 x 16 in	10,368 cu in	6.000 cu ft	44.88 gal	+4.88 gal
“55 gal”	48 x 13 x 21 in	13,104 cu in	7.583 cu ft	56.71 gal	+1.71 gal
“75 gal”	48 x 18 x 21 in	18,144 cu in	10.500 cu ft	78.52 gal	+3.52 gal
“125 gal”	72 x 18 x 22 in	28,512 cu in	16.500 cu ft	123.43 gal	-1.57 gal

Aquarium formula: L x W x H (inches) / 231 = US gallons actual. Actual dimensions may vary by manufacturer. “Nominal” gallon labels are trade designations, not certified volume measurements. For chemical dosing and filtration rating: always use actual cubic-inch calculation. NIST at NIST.gov. American Fisheries Society at Fisheries.org.

Three Real US Examples: A Phoenix Pool Builder, a Chicago Reef Aquarist, and an Austin Rainwater Harvesting Homeowner

Example 1: A Scottsdale Pool Builder Calculating the Volume of a 16×32 ft Inground Pool to Order the Right Quantity of Chlorine Stabilizer

Pool: 16 x 32 ft, 3.5 ft shallow end, 6.5 ft deep end. Average depth: (3.5 + 6.5) / 2 = 5.0 ft. Volume: 16 x 32 x 5.0 = 2,560 cu ft x 7.48052 = 19,150 US gallons. Cyanuric acid (CYA) dosing: 13 oz per 10,000 gal to raise 10 ppm. For 19,150 gal to reach 30 ppm CYA from 0: 3 x 13 oz x (19,150/10,000) = 74.9 oz = 4.68 lbs of CYA stabilizer needed.

Scottsdale, Arizona pool contractor Carlos is building a residential inground pool for a client. The pool is 16 feet wide, 32 feet long, with a 3.5-foot shallow end and a 6.5-foot deep end (average 5.0 feet). He needs to calculate the total water volume to order chemicals for the initial fill and to size the pool equipment.

Volume calculation: 16 ft x 32 ft x 5.0 ft average depth = 2,560 cubic feet. 2,560 cu ft x 7.48052 = 19,150 US gallons. Weight of water: 2,560 cu ft x 62.37 lb/cu ft = 159,667 lb = 79.8 US tons (relevant for structural engineering and foundation soil load calculations in Arizona clay soils). For chlorine shock (initial fill): 19,150 gal / 10,000 x 2 lbs Cal-Hypo = 3.83 lbs shock for first treatment. For CYA stabilizer from 0 to 30 ppm: 19,150 gal / 10,000 x 13 oz x 3 = 74.9 oz = 4.68 lbs. Pool pump sizing: typical turnover rate = pool volume / 8 hours. 19,150 gal / 8 h = 2,394 GPM minimum; a 1-HP pool pump at 2,200-2,700 GPM covers this pool. CDC pool safety at CDC.gov/healthywater. NSF/ANSI 50 at NSF.org.

Example 2: A Chicago Reef Aquarist Building a Custom 48x24x24 Inch Marine Tank and Calculating Actual Volume, Salt Mix, and Protein Skimmer Rating

Custom tank: 48 x 24 x 24 inches = 27,648 cu in / 231 = 119.69 US gallons = 16.0 cu ft. With sump (20-gal, 2.674 cu ft): total system = 16.0 + 2.674 = 18.674 cu ft = 139.7 US gallons. Salt mix: 0.5 cup (4 oz by weight) per gallon for 1.025 specific gravity. Total salt: 139.7 gal x 0.5 cup = 69.9 cups = about 17.5 lbs of aquarium salt mix.

Chicago marine biology teacher and reef hobbyist James is setting up a custom 48 x 24 x 24 inch rimless glass aquarium for a mixed reef system. He needs the actual gallon volume (not the nominal label), the total system volume including a 20-gallon sump, and the correct amount of salt mix for the initial fill.

Custom tank volume: 48 x 24 x 24 = 27,648 cubic inches / 231 = 119.69 US gallons = 27,648/1,728 = 16.0 cubic feet. Sump: 20-gallon sump = 20 x 231 = 4,620 cu in = 2.674 cu ft. Total system: 16.0 + 2.674 = 18.674 cu ft = 139.7 US gallons total water volume. Salt mix (Instant Ocean, Reef Crystals): approximately 0.5 cup or 0.36 lbs per gallon to reach 1.025 specific gravity (35 ppt salinity). Total salt: 139.7 gal x 0.36 lbs = 50.3 lbs of salt mix. That is about 5 standard 10-lb bags. Protein skimmer rating: size for 1.5-2x total system volume. 139.7 x 1.75 = 245 gallon-rated skimmer minimum. Note: the nominal “120-gallon” aquarium label would give a 14.3% error in salt calculation vs the actual 119.69-gallon figure. USGS water density at USGS.gov. AFS at Fisheries.org.

Example 3: An Austin Homeowner Calculating Annual Rainwater Harvesting Potential from a 2,500 Square Foot Roof

Austin, TX: average annual rainfall = 34.2 inches. Roof area: 2,500 sq ft (one-story 2,500 sq ft home, full footprint catchment). Annual rainfall volume: 2,500 sq ft x 34.2 in / 12 = 7,125 cu ft x 7.48052 = 53,299 gal/year gross. At 85% collection efficiency: 45,304 usable gallons per year. Texas HB 3391 permits unlimited residential rainwater harvesting.

Austin software engineer and sustainability advocate Maya is planning a whole-house rainwater harvesting system. Her 2,500 sq ft single-story home has a metal roof (high collection efficiency). She wants to calculate her annual collection potential, the cistern size needed, and potential outdoor water savings in central Texas.

Volume per 1-inch rain event: 2,500 sq ft x 1 in / 12 = 208.33 cubic feet x 7.48052 = 1,558.4 US gallons per inch. Annual gross collection: 2,500 x 34.2 / 12 = 7,125 cu ft. 7,125 cu ft x 7.48052 = 53,299 US gallons per year. At 85% first-flush adjusted collection efficiency: 53,299 x 0.85 = 45,304 usable gallons/year. Cistern sizing: for outdoor irrigation (lawn and garden = typical 40% of household water), a 1,500-gallon cistern bridges a 1-2 week dry period between rains (Maya uses 60-80 gal/day outdoor irrigation). For whole-house use: Austin Water Supply One (indoor) = average 70 gal/person/day x 3 people x 365 = 76,650 gal/year. The 45,304 harvestable gallons covers about 59% of household needs. Cistern options: 1,500 gal = 200.4 cu ft, 5,000 gal = 668.0 cu ft, 10,000 gal = 1,336 cu ft. Texas law: HB 3391 permits unlimited rainwater harvest. EPA WaterSense at EPA.gov/watersense. USGS water use at USGS.gov.

Five Expert Tips: The 7.48 vs 7.5 Accuracy Difference, Aquarium Nominal Gallon Labels, Pool Formula for Round Pools, Water Weight for Structural Engineers, and Why the 231 Cubic Inch Gallon Has a Historical Root

Tip 1: Always Use 7.48052, Not 7.5, When Calculating Pool Volume

Many pool guides say “multiply cubic feet by 7.5 to get gallons.” This is wrong. The exact multiplier is 7.48051948… (= 1728/231). Using 7.5 gives a 0.26% overcount. On small pools (10,000 gallons): 0.26% error = 26 gallons. On large pools (25,000 gallons): 65 gallons over. On chemical dosing: if your pool volume is overstated by 65 gallons, and you dose 1 lb of Cal-Hypo per 10,000 gallons, you under-dose by 65/10,000 x 1 lb = 6.5 grams per treatment, not a huge error, but it accumulates over a season. For accurate pool chemical ordering, equipment sizing (pump turnover rate), salt chlorinator output, and heater energy calculations: always use 7.48052 (or 1,728/231 = 576/77 exact). CDC healthy swimming at CDC.gov/healthywater/swimming. NSF at NSF.org. EPA at EPA.gov.

Tip 2: Aquarium Nominal vs Actual Gallons: Why Your Filter and Skimmer Rating Should Match Actual Volume

Aquarium manufacturers use nominal gallon labels (10, 20, 29, 40, 55, 75, 125 gallons) as trade names, not certified volume measurements. The actual volume is calculated from real dimensions: L x W x H (inches) / 231. Key discrepancies: the 40-gallon breeder (36x18x16 in) actually holds 44.88 gallons (4.88 gallons more than labeled). The 55-gallon standard (48x13x21 in) holds 56.71 gallons. The 75-gallon (48x18x21 in) holds 78.52 gallons. This matters for: protein skimmer rating (should exceed actual volume), canister filter flow rate (gallons per hour rating), CO2 injection rate (mL per hour per actual gallon), medication dosing (ml per gallon is exact), and heat energy calculations (watts to raise 78 actual gallons, not 75). Formula: LxWxH (in) / 231. Or: LxWxH (in) / 1728 = cubic feet x 7.48052 = actual gallons. USGS water properties at USGS.gov. AFS at Fisheries.org.

Tip 3: Round Pool Volume Formula: Pi x Radius Squared x Depth x 7.48052

For round or oval pools and above-ground pools: Round: pi x radius(ft) squared x average depth(ft) = cubic feet x 7.48052 = gallons. Example: 15-ft diameter round pool, 4 ft deep. Radius = 7.5 ft. Volume = 3.14159 x (7.5 squared) x 4 = 3.14159 x 56.25 x 4 = 706.9 cubic feet x 7.48052 = 5,289 US gallons. Oval: use pi x (length/2) x (width/2) x depth x 7.48052. For a 12 x 24 ft oval, 4 ft deep: 3.14159 x 6 x 12 x 4 = 904.8 cu ft x 7.48052 = 6,766 US gallons. For irregular shapes: break the pool into rectangular and curved sections and add volumes. Always use the average depth (shallow + deep end / 2) for the depth figure. CPSC pool safety at CPSC.gov. CDC pool at CDC.gov.

Tip 4: Water Weight Per Cubic Foot for Structural Engineering and Deck Load Calculations

Water weighs 62.3701958 lb per cubic foot at 68 degrees F (standard temperature). Salt water: approximately 64 lb per cubic foot. Hot tub water at 104 degrees F: approximately 60.0 lb per cubic foot. For residential deck or rooftop load calculations: a 300-gallon hot tub = 300 gal / 7.48052 = 40.1 cubic feet x 62.37 lb = 2,501 lb water weight plus shell weight (approximately 500-700 lb). Total: approximately 3,100-3,200 lb on the deck, or about 32-40 lb/sq ft for a 100-sq-ft footprint. Most residential decks are engineered for 40-60 lb/sq ft live load; a hot tub at grade is fine but a rooftop or elevated installation requires structural engineering review. 1 cubic foot of concrete weighs approximately 145-150 lb (dry mix). USGS water density at USGS.gov. CPSC at CPSC.gov.

Tip 5: Rainwater Harvesting Potential: How to Calculate Cistern Size from Roof Area and Local Rainfall

Step 1: Find annual rainfall for your city (Weather.gov or NOAA). Examples: Houston 49 in, Dallas 37 in, Atlanta 52 in, Phoenix 8 in, Seattle 38 in, Miami 62 in. Step 2: Calculate annual gross volume = roof area (sq ft) x annual rainfall (in) / 12 x 7.48052 x collection efficiency (0.80-0.90 for metal roof, 0.70-0.85 for shingle roof). Step 3: Size cistern for 2-3 weeks of storage at your peak demand rate. If outdoor irrigation = 50 gal/day: 2-week cistern = 700 gallons = 93.6 cubic feet. Step 4: First-flush diverter: discard first 1 gallon per 100 sq ft of roof per rain event to remove bird droppings and debris. Texas HB 3391 permits unlimited residential rainwater harvesting without a permit. Colorado formerly prohibited rainwater collection but now allows up to 110 gallons per household without a permit. Check your state law. EPA WaterSense at EPA.gov/watersense. NOAA climate data at NCDC.NOAA.gov. USGS at USGS.gov.

Quick Reference: Common Cubic Foot Values Converted to US Gallons

Cu Ft	US Gallons	Liters	Water Wt (lb)	Reference	Source
1 cu ft	7.481 gal	28.317 L	62.37 lb	Basic unit. 1 in rain x 12 sq ft = 1 cu ft = 7.48 gal.	NIST.gov.
1.389 cu ft	10.39 gal	39.31 L	86.6 lb	Nominal “10-gal” aquarium (20x10x12 in). Actual = 10.39 gal.	NIST.gov.
7.583 cu ft	56.73 gal	214.76 L	471 lb	Nominal “55-gal” aquarium (48x13x21 in). Actual = 56.73 gal.	NIST.gov.
10.5 cu ft	78.55 gal	297.33 L	652 lb	Nominal “75-gal” aquarium (48x18x21 in). Actual = 78.55 gal.	NIST.gov.
27 cu ft	201.97 gal	764.55 L	1,684 lb	1 cubic yard. Concrete and bulk material reference.	NIST.gov.
83.33 cu ft	623.4 gal	2,359.7 L	5,194 lb	1 inch rain on 1,000 sq ft roof (1,000 x 1/12 = 83.33 cu ft).	NIST.gov. EPA.gov.
1,960 cu ft	14,661 gal	55,483 L	121,894 lb	14×28 ft pool, 5 ft avg depth. Average US inground pool.	CDC.gov.
2,560 cu ft	19,150 gal	72,490 L	159,667 lb	16×32 ft pool, 5 ft avg depth. Large inground pool.	CDC.gov.
1 cu ft (ref)	7.48051948… gal	28.317 L	62.37 lb	Exact: 1728/231 = 576/77 (480519 repeats). 1 gal = 231 cu in US law.	NIST Handbook 44.

Exact: 1 cu ft = 1728/231 = 576/77 US gal. Source: NIST.gov. Water weight at 68 F: USGS.gov. Pool: CDC.gov. Rainwater: EPA.gov/watersense. HVAC: Energy.gov.

Frequently Asked Questions: Cubic Feet to Gallons

1 cubic foot = 1728/231 = 576/77 = 7.480519480519… US liquid gallons (the digits 480519 repeat infinitely). This comes from: 1 US gallon = 231 cubic inches (exact, US legal definition) and 1 cubic foot = 1,728 cubic inches. Source: NIST Handbook 44, NIST.gov.

1 cubic yard = 27 cubic feet = 27 x 7.480519 = 201.974 US gallons = 764.555 liters. Water weight: 27 x 62.37 = 1,684 lb = 0.842 US tons at 68 degrees F.

1 US gallon = 231/1728 = 77/576 cubic feet = 0.133680555… cubic feet = 231 cubic inches. For aquarium volume in gallons: L x W x H (inches) / 231 = US gallons.

A standard 55-gallon aquarium (48 x 13 x 21 inches) = 13,104 cubic inches / 231 = 56.71 US gallons actual. The “55-gallon” label is nominal. For filtration, dosing, and CO2: use 56.7 gallons, not the nominal 55.

0.6234 US gallons per square foot per inch of rain (exact: 1/12 x 7.48052 = 0.62338). For a 1,000 sq ft roof: 1 inch of rain = 1,000 x 0.6234 = 623.4 US gallons. For any roof: gallons = sq ft x inches of rain x 0.6234.

16 x 32 ft pool with 5 ft average depth = 16 x 32 x 5 = 2,560 cubic feet x 7.48052 = 19,150 US gallons. Average depth = (shallow end + deep end) / 2. Adjust for your pool’s actual average depth.

1 cubic foot of pure water at 68 degrees F (20 degrees C) = 62.3701958 pounds (approximately 62.4 lb). 1 cubic foot x 7.48052 gallons x 8.34 lb/gallon = 62.37 lb. Salt water: approximately 64 lb per cubic foot.

10 cubic feet x 7.48052 = 74.805 US gallons = 283.17 liters. Water weight: 10 x 62.37 = 623.7 lb at 68 degrees F.

100 cubic feet x 7.48052 = 748.052 US gallons = 2,831.7 liters. Water weight: 6,237 lb = 3.12 US tons at 68 degrees F. 1 inch of rain on 1,200 sq ft = 100 cu ft = 748 US gallons.

The standard 40-gallon breeder aquarium (36 x 18 x 16 in) = 10,368 cubic inches / 1,728 = 6.0 cubic feet actual. Its actual gallon volume: 10,368 / 231 = 44.88 US gallons (the 40-gallon label is nominal; it holds 44.88 gallons).

Rectangular pool: Length(ft) x Width(ft) x Average Depth(ft) = cubic feet. Then x 7.48052 = US gallons. Average depth = (shallow end + deep end) / 2. Round pool: Pi x radius^2 x depth = cubic feet x 7.48052 = gallons. Always use the exact multiplier 7.48052, not 7.5.

US gallons = cubic inches / 231. This is the exact US legal definition: 1 US liquid gallon = 231 cubic inches. Example: 10-gallon tank (20 x 10 x 12 in) = 2,400 cu in / 231 = 10.39 gallons actual.

5 cubic feet x 7.48052 = 37.403 US gallons = 141.58 liters. Water weight: 5 x 62.37 = 311.9 lb at 68 degrees F.

A 50-gallon water heater = 50 US gallons = 50 / 7.48052 = 6.684 cubic feet of water capacity = 50 x 231 = 11,550 cubic inches = 189.27 liters.

A US 55-gallon drum = 55 x 231 = 12,705 cubic inches = 12,705 / 1,728 = 7.352 cubic feet = 208.197 liters. Note: a nominal 55-gallon aquarium has different dimensions and holds 56.71 gallons (slightly more than labeled, NOT the same as a 55-gallon drum).

A standard 75-gallon aquarium (48 x 18 x 21 in) = 18,144 cubic inches / 231 = 78.52 US gallons actual = 10.5 cubic feet. The “75-gallon” label is nominal; actual is 78.52 gallons. For filtration and skimmer sizing: use 78.5 gallons.

The approximation 7.5 gallons per cubic foot gives a 0.26% over-count vs exact 7.48052. On a 20,000-gallon pool: 7.5 produces 20,053 gallons vs actual 20,000 gallons (53 gallons over). For pool chemical dosing accuracy: always use 7.48052 (exact: 1728/231).

1 cubic meter = 1,000 liters = 264.172 US gallons = 35.3147 cubic feet. 1 cubic meter / 7.48052 = 35.31 cubic feet. 1 cubic foot = 28.317 liters. 1 US gallon = 3.785411784 liters.

14 x 28 ft pool with 5 ft average depth = 1,960 cubic feet x 7.48052 = 14,661 US gallons. With 4.5 ft average depth: 14 x 28 x 4.5 = 1,764 cu ft = 13,195 gallons. Average depth = (shallow end + deep end) / 2.

Atlanta averages 52 inches of annual rainfall. 2,500 sq ft x 52 in / 12 = 10,833 cubic feet x 7.48052 = 81,037 US gallons per year gross. At 85% collection efficiency: 68,881 usable gallons/year. Atlanta permits rainwater harvesting for outdoor use; check local ordinances for indoor use permits.

20,000 US gallons / 7.48052 = 2,673.5 cubic feet. Water weight: 2,673.5 x 62.37 lb = 166,786 lb = 83.4 US tons. A 20,000-gallon pool’s water weighs more than 83 tons, a key structural consideration for elevated or rooftop pool installations.

Related Volume Calculators

🔁 Gallons to Cubic Feet Reverse: 1 US gal = 0.13368 cu ft = 231 cu in. 50-gal heater = 6.68 cu ft. Pool gallons to cu ft. 🛢️ Gallons to Ounces 1 US gal = 128 fl oz (exact). UK gallon = 153.72 US fl oz (20% more). Pool and keg decoder. 🧪 Liters to Gallons 1 L = 0.2642 US gal. 28.317 L = 1 cu ft = 7.48 US gal. EU recipe liters to US gallons. 📏 Gallons to Liters 1 US gal = 3.785 L. 7.48 gal = 1 cu ft = 28.317 L. Pool volume in liters. Fuel tank metric. 📦 Cubic Yards to Gallons 1 cu yd = 27 cu ft = 201.97 US gal. Concrete volume to water content. Bulk material. 🍺 Fl Oz to mL 1 fl oz = 29.574 mL. 128 fl oz = 1 US gal = 3,785 mL. Aquarium chemical dosing mL. 🌱 Acres to Square Feet 1 acre = 43,560 sq ft. 1 inch rain on 1 acre = 3,630 cu ft = 27,154 US gal (acre-inch). 📐 Cubic Feet to Cu Yards 27 cu ft = 1 cu yd. Pool: 2,560 cu ft = 94.81 cu yd. Concrete and excavation volumes.

Legal Disclaimer and Editorial Transparency

The Cubic Feet to Gallons Converter on USCalculators.com is for educational and informational purposes only. Exact: 1 US liquid gallon = 231 cubic inches (US legal definition). 1 cubic foot = 1,728 cubic inches (= 12 cubed). Therefore 1 cubic foot = 1,728/231 = 576/77 = 7.480519480519… US liquid gallons (exact repeating decimal). Source: NIST.gov NIST Handbook 44. Water density at 68 degrees F: 62.3701958 lb per cubic foot. Source: USGS.gov. Pool volume formulas (rectangular: L x W x avg depth x 7.48052; round: Pi x r^2 x depth x 7.48052) are standard calculations; actual pool volumes may vary due to pool shell thickness, equipment displacement, and irregular shapes. Pool chemical dosing references are for general informational purposes only; always follow specific product label directions and test water chemistry before adding chemicals. Pool safety at CDC.gov/healthywater/swimming. NSF at NSF.org. EPA pool chemicals at EPA.gov. Aquarium dimensions and nominal gallon labels are based on commonly manufactured standard tank sizes; actual dimensions and volumes vary by manufacturer. Rainwater harvesting regulations vary by US state; consult local regulations before installing a rainwater collection system. EPA WaterSense at EPA.gov/watersense. NOAA climate data at NCDC.NOAA.gov. HVAC and water heater data: DOE at Energy.gov. CPSC pool barrier safety at CPSC.gov. This tool does not constitute professional engineering, hydrological, or construction advice.

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