Gallons to Liters Converter: US vs UK Imperial Gallon, MPG to L/100km Fuel Economy Decoder, and Common Tank Size Reference
1 US gallon = 3.785411784 liters exactly. 1 UK Imperial gallon = 4.54609 L. Three modes: single gallons to liters, Fuel Economy Decoder (MPG to L/100km for comparing American and European car specs), or batch up to 20 values. 16 presets from half-gallon to 200-gallon propane tank. EPA fuel economy reference included. Free PDF. WhatsApp share.
Gallons to Liters
Conversion Result
Formula and Context
Why US Gallons to Liters Is One of the Most Searched Unit Conversions in America
Pull up to a gas station in Montreal heading north from Burlington, Vermont, and the pump screen shows litres per 100 kilometres. Look at a German car’s spec sheet for its tank size, and it reads 60 litres. Try to buy bottled water at an international airport, and the labels say 500 mL or 1.5 L, never gallons. The United States uses gallons for fuel, water, milk, and a hundred other everyday commodities. Nearly every other country uses liters. This gap makes gallons-to-liters one of the most searched unit conversions in the US, especially among road-trippers crossing into Canada or Mexico, car shoppers comparing American MPG to European L/100km ratings, and homeowners sizing rain barrels or water heaters listed by European manufacturers.
The exact conversion is 1 US gallon = 3.785411784 liters. This is a mathematically derived exact value, not an approximation. The US gallon is legally defined as 231 cubic inches (Title 15, US Code, Chapter 6, Section 205 and Commerce Department standards). One inch equals exactly 2.54 centimeters (NIST Handbook 44). Therefore 1 cubic inch = 2.54³ = 16.387064 cubic centimeters = 16.387064 milliliters. And 1 US gallon = 231 × 16.387064 = 3,785.411784 mL = 3.785411784 liters. This is exact, not rounded. NIST Unit conversions at NIST.gov.
The US Gallon in Everyday American Life and Commerce
The gallon shows up everywhere in American daily life in ways most people never stop to think about. Milk comes in half-gallon and gallon jugs. Pool chemicals dose per 10,000 gallons. Paint is sold by the gallon. Lawn chemicals apply per 1,000 square feet or per gallon of water in the sprayer. Septic tank capacity is rated in gallons (a typical 3-bedroom home has a 1,000-1,250 gallon septic tank = 3,785-4,732 liters). Propane is priced per gallon, even though propane is technically a gas at room temperature (liquid propane is stored under pressure; 1 gallon of liquid propane weighs 4.24 lbs and contains 91,452 BTU of energy). RV fresh water tanks: 20-100 gallons (75.7-378.5 L). Industrial cooling towers: rated in gallons per minute (GPM); 100 GPM = 378.5 liters per minute. Firefighter hose flow: 95-250 GPM depending on nozzle = 359-946 liters per minute. All of these require gallons-to-liters conversion when comparing to international equipment, exporting products, or working with metric-standard suppliers.
The US is one of only three countries worldwide that has not officially adopted the metric system as its primary measurement system (the others being Myanmar and Liberia). The Metric Conversion Act of 1975 (Public Law 94-168) designated SI (metric) as the preferred US measurement system, but did not mandate it for commerce. The Fair Packaging and Labeling Act requires dual labeling on many consumer products (both US customary and metric). This is why your water bottle says “16.9 fl oz (500 mL)” and why this converter exists. NIST metric program at NIST.gov/metric. Metric Conversion Act at USC.house.gov.
How This Three-Mode US Gallons to Liters Calculator Works
Mode 1: Single Gallons to Liters
Enter any gallon value (whole or decimal). Toggle the checkbox if you need the UK Imperial gallon (4.54609 L) instead of the US gallon (3.785411784 L). Output: liters, milliliters, cups, and fluid ounces. The chart compares your input to four reference points: half-gallon (1.893 L), 5-gallon gas can (18.927 L), 15-gallon sedan tank (56.781 L), and 26-gallon F-150 tank (98.421 L). Context note explains the use case for that gallon quantity. 16 presets from 0.5 gal to 200 gal (half-gallon milk carton through 200-gallon residential propane tank).
Mode 2: Fuel Economy Decoder (MPG to L/100km)
This is the feature no top-10 competitor offers for this search. Enter US EPA miles per gallon (MPG). Output: L/100km (European fuel economy standard), plus an EPA reference table showing where your input lands relative to vehicles from Toyota Prius at 52 MPG through a Ford F-150 at 22 MPG. Optional: enter fuel price ($/gallon) and annual miles driven to get your annual fuel cost in dollars. The exact formula is L/100km = 235.214583 / MPG, derived from 1 US gallon = 3.785411784 L and 1 mile = 1.609344 km (both exact).
Mode 3: Batch Conversion
Enter up to 20 gallon values, one per line. Output: a table showing liters, mL, cups, and fluid ounces for each value. Useful for contractors converting a list of water storage tank sizes from a US supplier, or event planners converting beverage quantities for a metric-label order. Commas in numbers are ignored (entering “1,000” reads as 1000 gallons).
US Gallon vs UK Imperial Gallon: A Surprisingly Costly Mix-Up with Real Consequences
| Gallon Type | Liters | Fl Oz | Origin / Legal Basis | Where Used |
|---|---|---|---|---|
| US Liquid Gallon | 3.785411784 L | 128 fl oz | 231 in³. US Commerce Dept, 15 USC Ch.6. NIST Handbook 44. | USA, some Caribbean nations. |
| UK Imperial Gallon | 4.54609 L | 160 fl oz | UK Weights and Measures Act 1985. Defined as 10 lbs of water. | UK, Canada (officially metric, but fuel was historically Imperial). |
| US Dry Gallon | 4.40488377 L | N/A | 1/8 US bushel = 268.8025 in³. USDA grain measurement. | Agriculture only (grain, berries). Not used for fuel or liquids. |
| Difference | 4.54609 / 3.785411784 = 1.2009 (20.1% larger) | 160 vs 128 | Always specify US or UK when quoting gallons internationally. | Never assume; always clarify in international contracts. |
Sources: US gallon: NIST Handbook 44 at NIST.gov. UK Imperial gallon: UK Weights and Measures Act 1985 at legislation.gov.uk. US Dry Gallon: USDA Agricultural Marketing Service at USDA.gov.
Common US Gallon to Liter Reference Values
| US Gallons | Liters | Milliliters | Context |
|---|---|---|---|
| 0.5 gal | 1.893 L | 1,893 mL | Half-gallon milk/OJ carton. Most common US refrigerator-door item. |
| 1 gal | 3.785 L | 3,785 mL | One-gallon water jug. Standard US paint can. 1 US gallon = 3.785411784 L (exact). |
| 5 gal | 18.927 L | 18,927 mL | 5-gallon gas can (OSHA max). 5-gallon water cooler jug (office dispenser). |
| 10 gal | 37.854 L | 37,854 mL | Standard 10-gallon fish tank. Some compact car fuel tanks. |
| 13.2 gal | 49.967 L | 49,967 mL | Toyota Corolla (2023) fuel tank capacity. |
| 15 gal | 56.781 L | 56,781 mL | Mid-size sedan fuel tank. Honda Accord: 14.8 gal, Toyota Camry: 14.5 gal. |
| 20 gal | 75.708 L | 75,708 mL | Small-to-mid SUV range. Honda CR-V: 14 gal. Toyota RAV4: 14.5 gal. |
| 26 gal | 98.421 L | 98,421 mL | Ford F-150 standard fuel tank. Full = 98.4 liters. |
| 36 gal | 136.275 L | 136,275 mL | Ford F-250 Super Duty dual-tank option. Long-haul capability. |
| 50 gal | 189.271 L | 189,271 mL | Standard US rain barrel. 50-gallon residential water heater. |
| 100 gal | 378.541 L | 378,541 mL | Large water storage tank. Large residential propane tank (above-ground). |
| 200 gal | 757.082 L | 757,082 mL | Typical above-ground residential propane tank size. |
Formula: liters = gallons x 3.785411784. All values exact per NIST gallon definition. Fuel tank sizes from manufacturer specifications; actual capacity varies slightly by model year and trim. EPA fuel economy data from FuelEconomy.gov.
Three Real US Examples: Cross-Border Road Trip Fuel, Car Spec Sheet MPG vs L/100km, and Rainwater Harvesting Tank Sizing
Example 1: A Texas Driver Converting F-150 Fuel Tank to Liters Before a Road Trip to Mexico
Single: 26 gal = 26 x 3.785411784 = 98.42 L. Mexico prices fuel by liter ($MXN per liter). 26 gal x 3.785411784 = 98.421 L. At MXN 23/liter (~$1.33 USD) the fill-up costs ~MXN 2,264 (~$130 USD). US price at $3.50/gal: 26 x $3.50 = $91.00.
Dallas resident Maria is driving her Ford F-150 to Monterrey, Mexico for a family visit. She wants to know how many liters her truck’s 26-gallon fuel tank holds because Mexican gas stations price fuel in pesos per liter. She also wants to compare the price. Her F-150 gets 22 MPG on the highway.
Single conversion: 26 US gallons = 26 x 3.785411784 = 98.42070638 liters. Her truck tank holds 98.4 liters. At a Monterrey PEMEX station priced at MXN 23.50 per liter, a full fill-up costs MXN 2,313 (approximately $132 USD at a 17.5:1 exchange rate), versus $91 at $3.50/gal in Dallas. Fuel economy: 22 MPG = 235.214583 / 22 = 10.69 L/100km. For her 950 km (590 mile) trip from Dallas to Monterrey, fuel consumption = (590 / 22) x 98.421 = approximately 2,642 miles per gallon… wait, correctly: 590 miles / 22 MPG = 26.8 gallons needed = 101.5 liters needed. She will need just over one full tank. Plan a PEMEX stop with the tank at half (approximately 13 gallons). EPA fuel economy data at FuelEconomy.gov. PEMEX fuel pricing at PEMEX.com. Mexican customs fuel import rules at SAT.gob.mx.
Example 2: A Seattle Car Shopper Comparing a US Car at 30 MPG to a German Import at 6.5 L/100km
Fuel Decoder: 30 MPG = 235.214583 / 30 = 7.84 L/100km. German car spec: 6.5 L/100km. MPG equiv = 235.214583 / 6.5 = 36.2 MPG. The German car is about 20% more fuel efficient than the 30 MPG US car.
Seattle buyer James is comparing a Toyota Camry (EPA 32 MPG combined) to a BMW 3 Series (European spec listed as 6.5 L/100km combined). He wants to know which is more fuel efficient in real-world terms, and whether the German car’s fuel economy advantage is significant enough to affect his total cost of ownership.
Fuel Economy Decoder: Toyota Camry 32 MPG = 235.214583 / 32 = 7.35 L/100km. BMW 3 Series European spec 6.5 L/100km = 235.214583 / 6.5 = 36.2 MPG (US). The BMW is about 13% more fuel efficient than the Camry (36.2 vs 32 MPG). Over 15,000 miles/year at $3.80/gal: Camry uses 15,000 / 32 = 468.75 gal x $3.80 = $1,781/year. BMW (US-market EPA, typically slightly lower than European spec at 30-32 MPG estimated): 15,000 / 31 = 483.9 gal x $3.80 = $1,839/year. In practice, the US-spec BMW may match the Camry on EPA combined rating; European L/100km specs are often tested on lighter European drive cycles than EPA. Check the US EPA window sticker at fueleconomy.gov for the actual US-spec BMW MPG. EPA fuel comparison tool at FuelEconomy.gov. US Department of Energy alternative fuel data at AFDC.energy.gov. IRS standard mileage rate at IRS.gov.
Example 3: An Austin Homeowner Sizing a Rainwater Harvesting System in Gallons and Liters
Batch: 50 gal (standard barrel) = 189.271 L. 500 gal (large storage) = 1,892.706 L. 2,500 gal (cistern) = 9,463.529 L. Texas allows unlimited rainwater collection. Austin Water: 1 inch of rain on 1,000 sq ft roof = approximately 625 gallons = 2,365 liters of collectible water (with 0.9 efficiency factor).
Austin homeowner Linda wants to install a rainwater harvesting system. Her 1,800 sq ft roof receives an average of 32 inches of rain per year. She is comparing a US supplier’s 500-gallon tank to a European manufacturer’s 2,000-liter tank. She needs to know which is larger, and how much annual rainwater she can collect.
Batch conversion: 500 gal = 500 x 3.785411784 = 1,892.705892 liters. 2,000 liters = 2,000 / 3.785411784 = 528.34 gallons. The European 2,000-liter tank is slightly larger (528 vs 500 gallons). Annual collection estimate: 1,800 sq ft x 32 inches/yr x 0.623 gallons/sq-ft/inch x 0.90 efficiency = 32,310 gallons/year = 122,250 liters/year. A 500-gallon (1,893 L) tank captures about 1.5% of annual rainfall; a 2,000-liter (528-gallon) tank catches about the same. For meaningful storage, 2,500+ gallons (9,464+ L) is more practical for an 1,800 sq ft Austin roof. Texas rainwater law at TCEQ.Texas.gov. Austin Water rainwater harvesting rebates at AustinTexas.gov. EPA WaterSense at EPA.gov/WaterSense.
Four Expert Tips: US vs UK Gallon Mistakes, Reading EPA Stickers, $/Gal to $/Liter, and Tank Sizing for Hot Water Heaters
Tip 1: The Gallon Confusion That Actually Costs US Travelers and International Buyers Real Money
Canada switched from Imperial gallons to liters for fuel in 1979. But older Canadians still reference the Imperial gallon informally. A US driver told that a Canadian generator “uses 2 gallons per hour” needs to know: 2 US gallons/hr = 7.57 L/hr; 2 Imperial gallons/hr = 9.09 L/hr. A 20% difference. In marine fuel planning, a boater buying a 200-gallon fuel tank from a US manufacturer (757 liters) versus a 200-Imperial-gallon tank from a UK supplier (909 liters) is getting nearly 150 liters more with the UK tank — a significant capacity difference. For oil and gas: international crude oil trading uses barrels (1 US petroleum barrel = 42 US gallons = 158.987 liters), but UK oil field reports sometimes reference Imperial barrels (42 UK Imperial gallons = 190.937 liters). Always confirm which gallon. US NIST unit standards at NIST.gov. UK Measurement Regulations at gov.uk/guidance.
Tip 2: Reading EPA Fuel Economy Window Stickers: MPG, L/100km, and What MPGe Means
Every new car sold in the US includes an EPA Monroney sticker (window label) showing city, highway, and combined MPG. The formula to convert to the European standard: L/100km = 235.214583 / MPG. So a Toyota Prius at 52 MPG combined = 4.52 L/100km; a Chevrolet Tahoe at 17 MPG combined = 13.84 L/100km. For electric vehicles, EPA uses MPGe (miles per gallon equivalent): 33.7 kWh of electricity equals the energy in 1 US gallon of gasoline (per Energy Policy Act). A Tesla Model 3 rated at 138 MPGe = 235.214583 / 138 = 1.70 L/100km electricity equivalent. This matters for comparing EVs to European cars rated in kWh/100km (the direct European EV metric). To convert: kWh/100km = (33.7 / MPGe) x (1.609344 / 3.785411784) x 100 (approximately). US DOE/EPA fuel economy tools at FuelEconomy.gov. Alternative Fuels Data Center at AFDC.energy.gov.
Tip 3: Converting Fuel Price from $/Gallon to $/Liter for International Price Comparison
Converting US fuel prices from $/gallon to $/liter is straightforward: $/liter = $/gallon / 3.785411784. At $3.50/gallon (common US regular unleaded average in 2024 per EIA): $3.50 / 3.785411784 = $0.924/liter. Canada prices gasoline in cents per liter (Canadian dollars); at 175 CAD cents/liter ($1.75 CAD/liter), and a 1.36 USD/CAD exchange rate: $1.75 / 1.36 = $1.287 USD/liter = $1.287 x 3.785411784 = $4.87 USD/gallon. So Canadian pump prices look cheaper than they are in liter terms when the exchange rate and tank size are both different from US assumptions. Mexico’s PEMEX publishes pump prices in MXN/liter. EIA weekly US retail gasoline prices at EIA.gov. PEMEX pricing at PEMEX.com. CAD/USD exchange rate at FederalReserve.gov.
Tip 4: Sizing US Water Heaters, Aquariums, and Pool Chemical Dosing in Gallons vs Liters
US water heaters are labeled in US gallons: standard residential tanks run 30, 40, 50, and 80 gallons. In metric terms: 30 gal = 113.6 L, 40 gal = 151.4 L, 50 gal = 189.3 L, 80 gal = 302.8 L. Rule of thumb for sizing: 10-15 gallons (37.9-56.8 L) per person in the household. A family of four needs 40-60 gallons (151-227 L). For aquariums: “10-gallon tank” = 37.85 L, “55-gallon tank” = 208.2 L, “125-gallon tank” = 473.2 L. Chemical dosing for pools: most US pool chemical labels dose in ounces or cups per 10,000 gallons. 10,000 US gallons = 37,854 L = 37.854 cubic meters. For a 25,000-gallon (94,635 L) pool, multiply all doses by 2.5. US DOE water heater sizing at Energy.gov. EPA WaterSense at EPA.gov/WaterSense.
Tip 5: Common Mistakes Americans Make When Converting Gallons to Liters
The most common mistake is confusing US and UK gallons. A British recipe calling for “2 pints” uses UK Imperial pints (568 mL each = 1,136 mL total), while US pints are 473 mL each (= 946 mL total). A 20% difference that can ruin a recipe or make a fuel estimate significantly wrong. Second: assuming 1 gallon = 4 liters (the rough approximation). For casual estimates, yes: 1 US gal ≈ 3.8 L. But for fuel tank calculations, chemical mixing, or international orders, use the exact value: 3.785411784 L. A 2% error on a 10,000-gallon order is 200 gallons (757 liters) — worth hundreds of dollars. Third: forgetting that MPG and L/100km are inversely proportional. Better fuel economy = higher MPG but lower L/100km. When a European car is described as using “less than 7 L/100km,” that corresponds to greater than 33.6 MPG in US terms. Fourth: using “gallon” loosely in international shipping without specifying dry vs liquid vs Imperial. The three types differ by up to 20%. US trade documents should always specify “US liquid gallon” or use liters/cubic meters per INCO terms and international trade standards (ICC/UCP 600). ICC at ICCwbo.org. NIST handbook on customary units at NIST.gov.
Quick Reference: Common US Gallon Values Converted to Liters
| US Gallons | Liters (L) | mL | Common Use |
|---|---|---|---|
| 0.5 gal | 1.893 L | 1,893 mL | Half-gallon milk carton. US refrigerator standard size. |
| 1 gal | 3.785 L | 3,785 mL | 1-gallon water jug. Paint can. Bleach jug. Pool chemical. |
| 5 gal | 18.927 L | 18,927 mL | OSHA max gas can. 5-gallon water cooler jug. |
| 10 gal | 37.854 L | 37,854 mL | Standard 10-gallon aquarium. Small fuel tank. |
| 20 gal | 75.708 L | 75,708 mL | Mid-size car/SUV fuel tank. 20-gallon water tank. |
| 26 gal | 98.421 L | 98,421 mL | Ford F-150 standard fuel tank. Full up = 98.4 liters. |
| 50 gal | 189.271 L | 189,271 mL | Standard rain barrel. 50-gallon water heater. |
| 100 gal | 378.541 L | 378,541 mL | Large storage tank. Large water heater max size. |
| 1 gal (UK Imperial) | 4.546 L | 4,546 mL | UK Imperial gallon = 4.54609 L (20.1% larger than US gallon). |
Formula: liters = US gallons x 3.785411784 (exact). Source: NIST.gov gallon definition. Fuel tank sizes from manufacturer specs; check FuelEconomy.gov for your specific model. UK Imperial gallon: UK Weights and Measures Act 1985.
Frequently Asked Questions: Gallons to Liters
Related Volume Converters
Legal Disclaimer and Editorial Transparency
The Gallons to Liters Converter on USCalculators.com is provided for educational and informational purposes only. Conversion formula: 1 US gallon = 3.785411784 liters exactly (from 1 US gallon = 231 cubic inches, 1 inch = 2.54 cm, both exact per NIST). 1 UK Imperial gallon = 4.54609 liters (exact, UK Weights and Measures Act 1985). Fuel economy formula: L/100km = 235.214583 / MPG (derived from 1 mile = 1.609344 km exact and 1 US gallon = 3.785411784 L exact). EPA fuel economy figures from FuelEconomy.gov; actual fuel economy varies with driving conditions, vehicle maintenance, weather, and driver behavior. Fuel prices cited for illustrative purposes only; for current US retail gasoline prices see EIA at EIA.gov. Fuel tank sizes from manufacturer specifications; check your specific vehicle model-year documentation for exact capacity. Rainwater harvesting legality varies by state and municipality; check local regulations before installation. Texas TCEQ rainwater rules at TCEQ.Texas.gov. Water heater sizing guidance from DOE at Energy.gov. All outbound links are provided for educational authority only. This tool does not constitute engineering, fuel efficiency, or investment advice.