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Litres to Gallons: US, Imperial and Everything Between

Convert litres to US and imperial gallons, quarts, pints, fluid ounces and cubic feet at once, and back again from gallons to litres.

L

The metric side. A litre is exactly a cubic decimetre — a 10 cm cube — which is the only definition in this whole page that is exact by design.

gal

Converted the other way below, in both gallon systems, so you can see how far apart they are.

US gallons

5.2834gal

A US gallon is exactly 231 cubic inches, which works out at 3.785411784 litres. It is the gallon on an American fuel pump and in a US recipe.

Imperial gallons
4.3994gal

Defined as exactly 4.54609 litres — originally the volume of ten pounds of water. It is about 20% larger than the US gallon, and the gap is why fuel economy figures never compare directly.

How much bigger the imperial gallon is
20.09%

The same fixed difference at any volume. Twenty per cent is enough to turn a good fuel figure into an ordinary one.

US quarts
21.134qt

A quarter of a US gallon, and near enough a litre that recipes swap them — a quart is 5% under a litre, which matters in baking and not in soup.

US pints
42.268pt

Sixteen US fluid ounces.

Imperial pints
35.195pt

Twenty imperial fluid ounces, and the reason a pint of beer in London is noticeably larger than one in New York.

US fluid ounces
676.28fl oz

The US fluid ounce is slightly *larger* than the imperial one, even though the US gallon is smaller. The two systems disagree in both directions at once.

Imperial fluid ounces
703.9fl oz
US cups
84.535cups

The legal US cup used on nutrition labels is 240 ml, a shade larger than the 236.6 ml customary cup used here. Metric cups elsewhere are 250 ml.

Cubic feet
0.70629ft³

For tanks and shipping, where volume stops being sold in gallons. A cubic foot is about 7.48 US gallons.

Cubic inches
1,220.47in³

The unit the US gallon is actually defined in — 231 of these, exactly.

Millilitres
20,000ml
Your gallons, if they are US gallons
18.9271L

The reverse conversion. 5 gal is this many litres in the US and 22.7305 L in imperial — the same number meaning two different volumes.

And if they are imperial gallons
22.7305L
Weight if it is water
44.092lb

A litre of water is a kilogram by design, so this is just the litres in pounds. Fuel is lighter, at roughly three quarters of that.

How to use this calculator

  1. Type a number into the Litres field to convert metric volume into US gallons, imperial gallons, quarts, pints, and other units simultaneously.
  2. Inspect the US gallons result and the imperial gallon result side by side to see the difference between the two systems.
  3. Scroll down to check specialised units including US cups, cubic feet, cubic inches, millilitres, and fluid ounces.
  4. Enter a value into the Or gallons, to convert back field to translate gallons directly back into litres.
  5. Review the water weight calculation in pounds to estimate the mass of the volume entered.

Understanding <strong>litres to gallons</strong> conversions

Converting litres to gallons sounds straightforward until you encounter the fundamental split in liquid measurement: the US gallon and the imperial gallon are entirely different amounts. If you are looking at a recipe, a fuel economy figure, or an aquarium specification, confusing the two will throw your calculations off by nearly twenty percent. A litre is a metric unit defined precisely as a cubic decimetre, making it an exact standard worldwide. The gallon, however, traces its lineage back through historical English wine and ale measures, resulting in two modern surviving standards that refuse to align.

When you use a litres to gallons converter, the underlying mathematics must handle this divergence immediately. One US gallon equals exactly 3.785411784 litres, stemming from its definition as 231 cubic inches. Meanwhile, the imperial gallon used historically across the British Commonwealth equals exactly 4.54609 litres. This means an imperial gallon is approximately 20.09 percent larger than a US gallon. If you type an l to gal value into the fields above, the tool divides your input by these precise divisors to run both conversions concurrently so you never mix them up.

The hidden trap: <strong>us gallon vs imperial gallon</strong>

The most common and costly mistake people make when performing gallons to litres or reverse operations is assuming all gallons are identical. A car advertised as getting 30 miles per gallon in the United States will achieve a significantly different numerical fuel economy rating in the United Kingdom even if the vehicle efficiency is identical, purely because the imperial gallon is larger. Similarly, shipping liquids internationally requires precise distinction between a US liquid pint and an imperial pint. A US pint contains 16 US fluid ounces, whereas an imperial pint contains 20 imperial fluid ounces. Curiously, the US fluid ounce is actually slightly larger than the imperial fluid ounce, adding another layer of complexity to sub-unit conversions.

The table below outlines common conversion checkpoints across both systems to give you a clear reference frame for typical volumes.

Litres (L)US Gallons (gal)Imperial Gallons (gal)Water Weight (lb)
1 L0.26 gal0.22 gal2.20 lb
5 L1.32 gal1.10 gal11.02 lb
10 L2.64 gal2.20 gal22.05 lb
20 L5.28 gal4.40 gal44.09 lb
50 L13.21 gal11.00 gal110.23 lb
100 L26.42 gal22.00 gal220.46 lb

Breaking it down: Quarts, pints, and ounces

Beyond the headline results for litres to gallons, everyday applications often demand smaller subdivisions like quarts, pints, and cups. The l to gal utility splits your input across these secondary units automatically. For instance, one litre equals approximately 1.056 US quarts or 2.113 US pints. When dealing with cooking ingredients or baking formulas, US cup measurements become essential, where one litre translates to roughly 4.226 cups.

For engineering and shipping contexts, cubic measurements provide absolute precision. One litre occupies 61.0237 cubic inches, while it takes roughly 28.3168 litres to make a single cubic foot. These volumetric conversions ensure that whether you are calculating engine displacement, box capacities, or fluid flow rates, the output matches standard industrial requirements without rounding errors.

When to trust the numbers and when to seek professional advice

While mathematical conversions between volume units are absolute and precise based on agreed international standards, real-world application introduces variables that a pure mathematical formula cannot account for. Temperature and pressure alter fluid volume significantly. Water expands as it heats up near boiling point or freezes into ice, meaning a fixed number of litres will occupy a different physical space under extreme thermal conditions. Furthermore, commercial measurement instruments such as fuel pumps or industrial flow meters often have legal tolerance thresholds and calibration drift.

You should not rely on standard volumetric conversions for high-precision chemical dosing, pharmaceutical compounding, or legal trade transactions where fiscal metering regulations apply. In those critical scenarios, consult certified metrologists, equipment calibration manuals, or industry-specific standards bodies rather than general digital conversion tools.

The formula

1 US gallon = 3.785411784 L, defined as exactly 231 cubic inches1 imperial gallon = 4.54609 L, exactly, and 20% largera US pint is 16 fl oz; an imperial pint is 20the US fluid ounce is larger than the imperial one, despite the smaller gallon

Frequently asked questions

How many litres are in a US gallon?

One US liquid gallon is legally defined as exactly 231 cubic inches, which converts to 3.785411784 litres. This standard is used primarily in the United States for retail fuel, milk jugs, and standard liquid measure. When performing standard conversions, rounding to 3.785 litres is sufficient for most everyday domestic tasks.

What is the difference between a US gallon and an imperial gallon?

The imperial gallon is an older British measurement standard defined as exactly 4.54609 litres. This makes an imperial gallon roughly 20 percent larger than a US gallon. Failing to account for this difference is a common error in international trade, automotive fuel economy comparisons, and recipe scaling.

How do I convert litres to gallons manually?

To convert litres to US gallons, divide your litre figure by 3.785. To convert litres to imperial gallons, divide your litre figure by 4.546. Conversely, to go from US gallons back to litres, multiply your gallon total by 3.7854.

Are US pints and imperial pints the same size?

No, they differ significantly. A US pint contains 16 US fluid ounces, whereas an imperial pint contains 20 imperial fluid ounces. Interestingly, because of historical inch definitions, a US fluid ounce is actually fractionally larger than an imperial fluid ounce, despite the overall US gallon being smaller.

How much does one litre of water weigh?

Under standard atmospheric conditions at 4 degrees Celsius, one litre of pure water has a mass of exactly one kilogram, which equals approximately 2.2046 pounds. This simple ratio makes it easy to estimate the physical weight of large volumes of water when planning transport or structural support.

Sources

Last reviewed . Results are for general guidance and are not professional advice.