CalcDuck

Volume Converter

Volume Converter

Converted value
3.785412
Conversion factor
1 gallonUS = 3.7854118 l

A US gallon is exactly 3.785411784 liters, while an imperial (UK) gallon is exactly 4.54609 liters, about 20 percent larger. A US cup is exactly 236.5882365 ml, or 8 US fluid ounces, and this converter keeps every US and imperial unit clearly labeled.

Tip: “Copy with settings” shares a link that opens this calculator with your numbers already filled in.

How this calculator works

Pick a from-unit and a to-unit and type a value; the conversion and the exact factor for that pair appear instantly. Recipe measurements (teaspoons, tablespoons, cups, fluid ounces) are included alongside metric liters and milliliters and larger US and imperial gallons, pints and quarts.

US customary and imperial (UK) units share several names, such as pint, quart, gallon and fluid ounce, but the two systems use different underlying sizes. Every option below is labeled US or imperial so it is never ambiguous which system a value belongs to.

How it converts

result = value × (liters per from-unit) ÷ (liters per to-unit)US anchors: 1 gal (US) = 3.785411784 L · 1 cup (US) = 236.5882365 ml = 8 fl oz (US) · 1 fl oz (US) = 29.5735295625 mlImperial anchors: 1 gal (imperial) = 4.54609 L exactly · 1 fl oz (imperial) = 28.4130625 ml

Worked example: 1 US gallon to imperial gallons

  1. 1 US gallon = 3.785411784 liters.
  2. 3.785411784 L ÷ 4.54609 L per imperial gallon ≈ 0.8327 imperial gallons.
  3. So a US gallon is about 83% of an imperial gallon — the reason US and UK fuel-economy and recipe figures are not directly comparable without converting.

Frequently asked questions

Is a US cup the same as a metric cup?

No. The US legal/customary cup used here is exactly 236.5882365 ml. A metric cup, used in Australia and some recipe books, is defined as exactly 250 ml.

Are US and imperial (UK) tablespoons the same?

No. A US tablespoon is exactly 14.78676478125 ml. A UK tablespoon is commonly taken as 15 ml (or historically 17.7 ml); this converter's imperial units follow the fluid-ounce-based imperial system rather than the informal UK cooking tablespoon.

Why are US and imperial gallons different sizes?

They come from separate historical definitions. The US gallon derives from an old English wine gallon; the imperial gallon was redefined in 1824 as the volume of 10 pounds of water. The imperial gallon ends up about 20% larger.

How many fluid ounces are in a US cup?

Exactly 8 US fluid ounces, since the US cup is defined as 1/16 of a US gallon and there are 128 US fluid ounces in a US gallon.

How many milliliters are in a liter?

Exactly 1,000. The metric prefix 'milli' means one-thousandth, so 1,000 ml always equals 1 L — the same metric relationship this page's US anchors, like 236.5882365 ml per US cup, are ultimately expressed against.

Sources

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