Convert Liters to Gallons

A US gallon is exactly 3.785411784 liters. An imperial gallon is exactly 4.54609 liters. An imperial gallon is 20% larger. The wrong choice ruins fuel calculations, recipe yields, and industrial orders. This converter tells you which gallon you actually need.

The math is a single multiplication. No division to remember and no guesswork about which formula to use, because the formula itself tells you which gallon you are using.

Liters to US Gallons

Multiply the liter value by 0.264172. That factor is derived from the NIST definition: 1 US gallon = 3.785411784 L, so 1 ÷ 3.785411784 = 0.2641720523. For most work, five decimal places are enough. For 10 liters: 10 × 0.264172 = 2.64172 US gallons.

Liters to Imperial Gallons

Multiply the liter value by 0.219969. This comes from the UK Weights and Measures Act 1985 definition: 1 imperial gallon = 4.54609 L, so 1 ÷ 4.54609 = 0.2199692483. For 10 liters: 10 × 0.219969 = 2.19969 imperial gallons.

The two formulas produce results that differ by about 20%. That gap is the whole reason this converter exists. Always check which gallon your context uses before you multiply.

Run these through the calculator to confirm the pattern. Each row uses the exact factors above.

1 Liter

• 1 L = 0.2642 US gallons
• 1 L = 0.2200 imperial gallons

A standard 1-liter water bottle is roughly a quarter of a US gallon. In the UK, a 1-liter bottle is about one-fifth of an imperial gallon. The difference matters when you are pouring ingredients into a recipe that uses gallons.

5 Liters

• 5 L = 1.3210 US gallons
• 5 L = 1.1000 imperial gallons

Five liters is a common car-engine oil bottle. If the spec sheet says the reservoir holds 1.3 US gallons, you pour the whole 5-liter bottle. If the spec uses imperial gallons, you need to buy 5.5 liters, a half-liter more.

20 Liters

• 20 L = 5.2840 US gallons
• 20 L = 4.4000 imperial gallons

A 20-liter jerry can is a standard fuel container. A US fuel station sells it as 5.28 gallons. A UK station sells it as 4.40 gallons. Driving from Canada into the US and filling a 20-liter can, the US pump will show about 5.3 gallons, not 4.4.

200 Liters

• 200 L = 52.8400 US gallons
• 200 L = 44.0000 imperial gallons

A 200-liter drum is a nominal 55-gallon drum. The real volume of a 55 US gallon drum is 208.2 liters, not 200. The 200-liter label is a rounding error that costs you 8.2 liters per drum. If you order by the drum and the spec sheet says 200 liters, check whether the supplier means 55 US gallons or 200 metric liters.

The table below covers the most common liter values you encounter in fuel, cooking, and industrial settings. For 1 to 200 liters, the US and imperial gallon values diverge by 0.04 to 8.8 gallons.

The wrong gallon choice produces a 20% error. The same error in a fuel economy calculation makes a 30 MPG car look like 36 MPG, or vice versa.

Context Clues

• Country of purchase: Buying fuel in the United States? The gallon is always US. Buying fuel in the United Kingdom? The gallon is imperial. Canada uses liters at the pump, not any gallon.
• Container labeling: A 5-gallon jug of water in a US grocery store is 5 US gallons (18.93 L). A 5-gallon jerry can sold in the UK is 5 imperial gallons (22.73 L). Check the small print: US containers often say "US gal" or just "gal"; UK containers say "UK gal" or "imperial gal".
• Recipe origin: US recipes use US cups (236.588 mL) and US fluid ounces (29.574 mL). UK recipes use imperial cups (284.131 mL) and imperial fluid ounces (28.413 mL). A US recipe calling for 1 gallon is a US gallon. A UK recipe calling for 1 gallon is an imperial gallon, though UK recipes rarely use gallons at all, they use pints and quarts.
• Industrial standard: A 55-gallon drum in the oil and chemical industries is a US gallon drum (208.2 L). The imperial equivalent is a 45-gallon drum (204.6 L), which is much less common. If the spec says 55 gal, assume US.

Decision Tree

Ask three questions in order. First: who wrote the measurement? If it is from the US government, a US company, or a US recipe, use the US gallon. Second: is the measurement from the UK government, a UK company, or a UK recipe? Use the imperial gallon. Third: if neither, look for the word "imperial" or "US". If the document says "gallon" without qualification, assume US, the US gallon is more widely used globally for trade, but never assume in a critical calculation. When in doubt, convert both ways and confirm which result matches reality.

The failure case: you enter 10 liters, pick the wrong gallon, and pour 2.64 L instead of 2.20 L into a UK recipe, or vice versa. Your recipe is 20% off, and your fuel cost comparison is off by the same margin.

This converter accepts a volume in liters and a choice of US gallons or imperial gallons. It applies the exact NIST or UK Weights and Measures factor, then displays the result in the selected unit. You can also see the conversion to milliliters, US fluid ounces, and imperial fluid ounces. The calculator shows the calculation steps: the input value, the formula, the substitution, and the final result in all supported volume units. You choose the decimal precision from 0 to 6 places. The reset button clears all inputs and returns the defaults.

This tool uses the same exact factors. It does not round the intermediate result. The displayed number is the multiplication of the input by the factor, rounded only to the decimal places you select.

The conversion factors are exact by law, not by convention. The US gallon is defined by NIST as 231 cubic inches, which is exactly 3.785411784 liters. The imperial gallon is defined by the UK Weights and Measures Act 1985 as 4.54609 liters. These numbers will not change. Do not round them to 3.8 or 4.0, that introduces an error larger than 1% for a simple conversion, and a 1% error on a 200-liter drum is 2 liters.

The one honest caveat: the NIST SP 811 edition you have may be from 2008, and the UK Weights and Measures Act is periodically amended. The definitions themselves are stable, but the legal reference can shift. For the US gallon, the current version of NIST Handbook 44 is the authoritative source. For the imperial gallon, the UK National Archives holds the current text of the 1985 Act. If you need the exact wording for a legal or engineering document, go to those sources directly.