Gallons to Liters Converter
Convert volume between US gallons, UK gallons, liters, milliliters, quarts, pints, cups, and fluid ounces. Complete volume conversion.
Gallons to Liters Converter
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Formula: L = US gal x 3.78541 | US gal = L / 3.78541 | 1 gal = 4 qt = 8 pt = 16 cups = 128 fl oz
Worked example — 15 US gal = 56.78 L = 12.49 UK gal
Formula
L = US gal x 3.78541 | US gal = L / 3.78541 | 1 gal = 4 qt = 8 pt = 16 cups = 128 fl oz
All volume conversions use milliliters as the base unit. One US gallon equals exactly 231 cubic inches or 3,785.41 mL. One UK (imperial) gallon equals 4,546.09 mL. The metric system uses liters (1 L = 1,000 mL = 1 cubic decimeter). US liquid measurements follow the hierarchy: gallon > quart > pint > cup > fluid ounce.
Worked Examples
Example 1: Fuel Tank Conversion
Problem:A car has a 15 US gallon fuel tank. How many liters does it hold?
Solution:Liters = US gallons x 3.78541 Liters = 15 x 3.78541 = 56.78 L Also: 15 US gal = 12.49 UK gal = 60 quarts = 120 pints = 240 cups
Result:15 US gal = 56.78 L = 12.49 UK gal
Example 2: Recipe Scaling
Problem:A recipe needs 500 mL of milk. How many cups is that?
Solution:Cups = mL / 236.588 Cups = 500 / 236.588 = 2.113 cups Approximately 2 cups and 2 tablespoons Also: 500 mL = 0.5 L = 16.91 fl oz
Result:500 mL = 2.11 cups = 16.91 fl oz = 0.132 US gal
Frequently Asked Questions
How do I convert gallons to liters?
To convert US gallons to liters, multiply by 3.78541. For example, 5 US gallons = 5 x 3.78541 = 18.927 liters. For UK (imperial) gallons, multiply by 4.54609. So 5 UK gallons = 5 x 4.54609 = 22.73 liters. A quick estimate for US gallons: multiply by 3.8 (or roughly 4 minus 5%). For UK gallons, multiply by 4.5. The US gallon is about 83% the size of the UK gallon.
What is the difference between US and UK gallons?
A US gallon equals 3.78541 liters (128 US fluid ounces), while a UK (imperial) gallon equals 4.54609 liters (160 imperial fluid ounces). The UK gallon is about 20% larger. This difference dates back to 1824 when Britain redefined the gallon as the volume of 10 pounds of water. The US retained the older Queen Anne wine gallon (231 cubic inches). This means fuel economy figures differ — 30 mpg (US) equals about 36 mpg (UK) and 7.84 L/100km.
How many cups are in a gallon?
There are 16 US cups in a US gallon. The breakdown is: 1 gallon = 4 quarts = 8 pints = 16 cups = 128 fluid ounces. For cooking, remember: 1 cup = 8 fl oz = 16 tablespoons = 48 teaspoons = 236.588 mL. A metric cup (used in Australia and some other countries) is 250 mL, slightly larger than a US cup. UK imperial cups are 284 mL (10 imperial fluid ounces) but are rarely used in modern recipes.
Why do recipes use different volume measurements worldwide?
The US uses cups, tablespoons, and fluid ounces; the UK traditionally uses imperial pints and fluid ounces (different sizes from US); and most other countries use metric (mL, L). This stems from historical measurement systems that developed independently. For precision, professional bakers worldwide prefer weight measurements (grams) over volume, since volume varies with how ingredients are packed. When following international recipes, always check which measurement system is used — a US cup (236 mL) differs from an Australian cup (250 mL) and a Japanese cup (200 mL).
How many liters are in a standard water bottle?
Standard single-serve water bottles typically hold 500 mL, which is 0.5 liters or about 16.9 US fluid ounces. Larger reusable bottles commonly come in 750 mL and 1-liter sizes. A 1-gallon water jug holds 3.785 liters. Five-gallon water cooler jugs hold 18.93 liters. Knowing these conversions helps when tracking daily water intake, as health guidelines often recommend 2 to 3 liters of water per day for adults.
What is the difference between a dry gallon and a liquid gallon?
The US dry gallon is approximately 4.405 liters, while the US liquid gallon is 3.785 liters. The dry gallon is about 16% larger and is used for measuring dry goods like grains, fruits, and vegetables. It derives from the Winchester bushel, where one dry gallon equals one-eighth of a bushel. In everyday use, the liquid gallon is far more common, and most references to gallons in cooking, fuel, and household measurements mean the liquid gallon. The dry gallon is rarely used outside of agricultural commodity trading.
How do I convert between milliliters and fluid ounces?
To convert milliliters to US fluid ounces, divide by 29.5735. To convert US fluid ounces to milliliters, multiply by 29.5735. For example, 100 mL equals about 3.38 fluid ounces, and 8 fluid ounces equals about 236.6 mL. Note that UK imperial fluid ounces are slightly different at 28.413 mL each. This conversion is especially useful for medication dosages, cosmetic formulations, and converting between metric and US recipes.
How many gallons of gas does a typical car tank hold?
Most passenger cars have fuel tanks ranging from 12 to 16 US gallons, which equals 45 to 61 liters. Compact cars typically hold 10 to 13 gallons (38 to 49 liters), sedans hold 13 to 16 gallons (49 to 61 liters), and SUVs or trucks hold 18 to 36 gallons (68 to 136 liters). Knowing the conversion helps when traveling internationally, as fuel is sold in liters in most countries outside the United States. At current fuel prices, the difference between gallons and liters is important for accurate cost comparisons.
What is the fastest way to estimate gallon to liter conversions in my head?
A quick mental shortcut for US gallons to liters is to multiply by 4 and subtract 5 percent. Since one gallon is 3.785 liters, multiplying by 4 gives 4.0, which is only about 5.7 percent too high. For liters to gallons, divide by 4 and add about 6 percent. Another approach is to remember that 5 gallons is almost exactly 19 liters, so you can scale from that ratio. For UK gallons, just multiply by 4.5 or remember that 2 UK gallons is about 9 liters.
Is 3.78541 an exact figure or a rounded one?
It is a rounded form of an exact value. The US liquid gallon is defined as exactly 231 cubic inches, and since the inch is defined as exactly 2.54 centimetres, a cubic inch is 16.387064 cubic centimetres. Multiplying gives 3,785.411784 millilitres, or 3.785411784 litres, with no approximation anywhere in the chain. The imperial gallon is likewise defined as exactly 4.54609 litres. Five decimal places is far more precision than any household or trade measurement can support.
References
Background & Theory
1 US liquid gallon = 3.785411784 litres exactly, and 1 litre = 0.264172052 US gallons. The exact figure follows from the gallon being defined as 231 cubic inches, with the inch itself exactly 25.4 mm.
Conversion reference table
| Conversion | Equivalent | Exact or rounded? |
|---|---|---|
| 1 US liquid gallon | 3.785411784 litres | Exact (231 cubic inches) |
| 1 imperial (UK) gallon | 4.54609 litres | Exact by definition |
| 1 litre | 0.264172052 US gallons | Derived, rounded |
| 1 US quart | 0.946352946 litres | Exact |
| 1 US pint | 0.473176473 litres | Exact |
| 1 US fluid ounce | 29.5735295625 millilitres | Exact |
| 1 imperial fluid ounce | 28.4130625 millilitres | Exact |
| 1 oil barrel | 42 US gallons = 158.987294928 litres | Exact |
The imperial gallon is about 20 percent larger than the US gallon, which is the single biggest trap in this family of units: a car rated at 30 miles per US gallon is 36 miles per imperial gallon on exactly the same fuel. The fluid ounces run the other way, with the imperial ounce the smaller of the two, because an imperial gallon splits into 160 ounces while a US gallon splits into 128.
Reviewed for accuracy by Manoj Kumar, Mathematics Educator · Editorial policy
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