Article — Liters to Gallons Converter
Liters to Gallons: convert L to gal with US and Imperial precision
One US gallon equals 3.785411784 liters. One Imperial (UK) gallon equals 4.54609 liters. Both factors are exact, set by NIST and by the UK Weights and Measures Act. To convert liters to US gallons, divide by 3.78541. For Imperial gallons, divide by 4.54609. The two gallons differ by about 20%, which is the single most common error in cross-Atlantic conversions.
The converter at the top of this page toggles between the two gallon systems and shows all four directions (L to US gal, US gal to L, L to Imp gal, Imp gal to L). The article below covers why the US and UK use different gallons, how to translate MPG into L/100 km, and the volumes where the conversion comes up most.
How many liters in a gallon?
There are two answers, both correct depending on which side of the Atlantic you are on. A US gallon contains 3.78541 liters. A UK Imperial gallon contains 4.54609 liters. The US gallon is smaller by about 20%, or one-fifth, of the Imperial gallon.
The same word means different volumes in different countries. American recipes, fuel pumps, and household products use the US gallon. British petrol economy figures, UK recipes, and Canadian historical references use the Imperial gallon. Both definitions are exact and legally fixed.
The 3.785411784 figure for the US gallon comes from defining it as exactly 231 cubic inches. Convert cubic inches to milliliters using the international inch (25.4 mm exact), and 231 × 25.4³ / 1000 = 3,785.411784 mL = 3.785411784 L. The factor is not measured; it is defined.
The liters-to-gallons formula
Divide liters by the gallon-system factor. The factor depends entirely on whether you mean a US or Imperial gallon. Both directions reverse cleanly.
L ÷ 3.78541 = US galUS gal × 3.78541 = LL ÷ 4.54609 = Imp galImp gal × 4.54609 = L1 Imp gal = 1.20095 US galFor mental math, a US gallon is “just under 4 liters” (3.79 L, 5.7% under), and an Imperial gallon is “a little over 4.5 liters” (4.55 L). Going the other way, a liter is “a quarter of a gallon plus a tiny bit” in US terms (0.264 gal) or “just over a fifth of a gallon” in Imperial terms (0.220 gal).
US gallon vs. Imperial gallon
The 20% difference between the two gallons is consequential. A car advertised at 50 MPG in the UK does not match a US car advertised at 50 MPG — the UK figure is for a 20%-larger gallon, so the actual fuel economy is about 16.7% lower in US terms (roughly 42 US MPG). Recipes calling for “a gallon of milk” produce different sized batches depending on the source country.
The fluid ounce confusion runs deeper. A US fluid ounce is 29.5735 mL; an Imperial fluid ounce is 28.4131 mL. So a US gallon has 128 US fl oz, and an Imperial gallon has 160 Imperial fl oz. The two ounce definitions differ by 4%, but the gallon definitions differ by 20% because the Imperial gallon uses more ounces.
MPG, L/100 km, and fuel economy
The US uses miles per gallon. Most of the rest of the world uses liters per 100 kilometers. The two metrics describe the same physical efficiency in inverse forms: MPG measures distance per fuel volume, while L/100 km measures fuel volume per distance.
Convert US MPG to L/100 km by dividing 235.21 by the MPG figure. The constant comes from converting 1 mile per US gallon to its equivalent: 1 US gal = 3.78541 L, 1 mile = 1.60934 km, so 1 MPG corresponds to (3.78541 / 1.60934 × 100) = 235.21 L/100 km when inverted. For Imperial MPG, the constant is 282.48 (using 4.54609 L per Imperial gallon).
L/100 km is the more honest metric for fuel-cost planning. Doubling fuel economy from 15 to 30 MPG saves twice the fuel per mile that doubling from 30 to 60 MPG saves. The inverse relationship hides this in the MPG view but is obvious in L/100 km. Use L/100 km when you are budgeting fuel for a trip; use MPG when you are bragging.
Liters to gallons quick reference
The volumes that come up most often: drink containers, fuel tanks, paint cans, household buckets, and small pools. Both US and Imperial conversions are shown.
- 1 L = 0.2642 US gal = 0.2200 Imp gal
- 2 L = 0.5283 US gal (standard 2-liter soda bottle)
- 5 L = 1.3209 US gal = 1.0998 Imp gal (small fuel jerry can)
- 10 L = 2.6417 US gal = 2.1997 Imp gal (large bucket)
- 18.93 L = exactly 5 US gal (the standard 5-gallon bucket)
- 20 L = 5.2834 US gal (compact car fuel tank)
- 60 L = 15.85 US gal (typical SUV or pickup fuel tank)
- 1,000 L = 264.17 US gal (IBC tank, 1 cubic meter)
Beverage labeling and pool volumes
US beverage labeling uses fluid ounces and fractions of a gallon for large containers. A “quart” of milk is 1/4 of a US gallon, which equals 946 mL — close to but not exactly a liter. A “half-gallon” of ice cream is 1.89 L. The metric equivalents are off by 5–6% in every direction, which is why imported beverages typically round to 1 L, 1.5 L, or 2 L sizes even when those are not the original product volumes.
Pool volumes are usually quoted in gallons in the US and liters elsewhere. A standard 27-foot-round above-ground pool holds about 19,400 US gallons or 73,400 liters. A standard backyard in-ground pool is around 20,000–25,000 gallons (75,000–95,000 L). Pool chemical dosing instructions assume the unit on the bottle matches the unit the customer measures in — mismatches cause overdose or underdose by the 20% gallon ratio.
UK pool chemical bottles dose for Imperial gallons. US bottles dose for US gallons. If you bring a UK bottle to a US pool, you under-dose by 20%. The reverse over-doses, which can be a chlorine-shock hazard. Always confirm the gallon system on chemical bottles before mixing in international contexts.
A brief history of the gallon
The English “wine gallon” of 231 cubic inches was standardized by Parliament in 1706 and adopted by the United States after independence. The number 231 was convenient because a cylinder 7 inches in diameter and 6 inches tall has a volume close to 231 cubic inches under the approximation pi = 22/7, letting coopers verify a barrel without complex math.
In 1824 the UK redefined the gallon as the volume of 10 pounds of distilled water at 62 °F — the Imperial gallon. The US kept the 1706 wine gallon. The two definitions have coexisted for two centuries with no prospect of unification.
Common liters-to-gallons mistakes
Most liters-to-gallons errors come from ambiguity about which gallon is meant. A few patterns repeat.
- Wrong gallon system: US and Imperial gallons differ by 20%. Always confirm which one a source means.
- Dry vs. liquid gallons: the US has a separate dry gallon (4.405 L) used for grain. Modern recipes use the liquid gallon.
- Fluid ounces are different sizes too: 1 US fl oz = 29.5735 mL, 1 Imp fl oz = 28.4131 mL. Recipe quantities scale differently.
- MPG comparisons across countries: a UK car at 50 MPG is roughly equivalent to a US car at 42 MPG, not 50 MPG.
- “A gallon” with no qualifier: in the US, it is a US gallon. In the UK, it is an Imperial gallon. In Canada, it depends on the speaker and decade.
- Pool and chemical dosing: bottles label dosing per gallon. Always match the gallon system to the volume measurement.