Volume Converter
Volume measurement systems diverged centuries ago across the Atlantic, leaving the US gallon at 3.785 litres and the UK gallon at 4.546 litres, a 20 percent difference that matters in cooking, chemistry, and commerce. This converter handles both traditions, cooking units (tablespoons, teaspoons, cups), and cubic units, all in a single step.
Formula
Worked example
1 US gallon: multiply by 3.785412 to get 3.785 L. Divide by 0.473176 for US pints = 8 pt. Divide by 4.54609 for UK gallons = 0.8327 UK gal.
How the converter works
Every unit is anchored to the litre, the SI-coherent unit defined as exactly one cubic decimetre (0.001 m3). The converter applies the fixed, exact conversion factors adopted by the International Bureau of Weights and Measures (BIPM) and the US National Institute of Standards and Technology (NIST). US customary units follow the legal definitions codified in NIST Handbook 44; UK imperial units are defined under the Weights and Measures Act 1985. When you enter a value, the tool first converts it to litres using the exact factor for the selected unit, then divides by the factor for every output unit simultaneously. Rounding is applied at the display level only; internal calculations retain full floating-point precision.
US liquid units and cooking units
The US gallon is exactly 231 cubic inches, which works out to 3.785411784 litres. It divides cleanly: 1 gallon = 4 quarts = 8 pints = 16 cups = 128 fluid ounces = 256 tablespoons = 768 teaspoons. A US customary cup is 236.588 mL, slightly smaller than the US legal cup (240 mL) used on nutrition labels. When following a recipe, check whether the source uses US customary or legal cups, especially for liquids close to the threshold of a rounding error. A US fluid ounce is 29.574 mL; do not confuse it with a UK fluid ounce (28.413 mL), which differs by about 4 percent.
UK imperial units
The UK gallon was defined in 1824 as the volume of exactly 10 pounds of water at 62 degrees Fahrenheit, yielding 4.54609 litres, about 20 percent larger than its US counterpart. The UK hierarchy mirrors the US one in names: 1 gallon = 4 quarts = 8 pints, but the actual volumes are all larger. A UK pint is 568 mL versus 473 mL for a US liquid pint. Many British recipes quote ingredients in pints and cups, and using US values will produce a noticeably different result, especially in baking where hydration ratios matter.
Metric and cubic units
Metric volume is built on the cubic metre (m3): 1 m3 = 1000 L = 1,000,000 mL = 1,000,000 cm3. This chain of powers-of-ten conversions makes metric arithmetic simpler. Cubic imperial units (cubic inch, cubic foot, cubic yard) appear in construction and engineering in the US and UK. One cubic foot is 28.317 litres; one cubic yard is 764.6 litres. For concrete, soil, and aggregate ordering, these matter: a cubic yard of material weighs roughly 1.3 US short tons for typical soil.
Volume conversion factors (relative to 1 litre)
| Unit | Litres per unit | Units per litre | System |
|---|---|---|---|
| 1 mL | 0.001 | 1000 | Metric |
| 1 cL | 0.01 | 100 | Metric |
| 1 dL | 0.1 | 10 | Metric |
| 1 L | 1 | 1 | Metric |
| 1 cm3 | 0.001 | 1000 | Metric |
| 1 m3 | 1000 | 0.001 | Metric |
| 1 tsp (US) | 0.004929 | 202.88 | US cooking |
| 1 tbsp (US) | 0.014787 | 67.628 | US cooking |
| 1 cup (US) | 0.23659 | 4.2268 | US cooking |
| 1 fl oz (US) | 0.029574 | 33.814 | US liquid |
| 1 pt (US) | 0.473176 | 2.11338 | US liquid |
| 1 qt (US) | 0.946353 | 1.05669 | US liquid |
| 1 gal (US) | 3.785412 | 0.26417 | US liquid |
| 1 fl oz (UK) | 0.028413 | 35.1951 | UK imperial |
| 1 pt (UK) | 0.568261 | 1.75975 | UK imperial |
| 1 qt (UK) | 1.136523 | 0.87988 | UK imperial |
| 1 gal (UK) | 4.54609 | 0.21997 | UK imperial |
| 1 in3 | 0.016387 | 61.024 | Cubic imperial |
| 1 ft3 | 28.3168 | 0.035315 | Cubic imperial |
| 1 yd3 | 764.555 | 0.0013080 | Cubic imperial |
All factors are exact or carry the full NIST/BIPM precision. Multiply the litre value by the factor to get the target unit.
Frequently asked questions
Why is a US gallon smaller than a UK gallon?
The two systems descend from different historical English wine and ale measures standardised independently. The US gallon was fixed at 231 cubic inches (3.785 L) by Congress in 1836, while the UK gallon was redefined in 1824 as the volume of exactly 10 pounds of water at 62 degrees Fahrenheit (4.546 L). The definitions have remained separate ever since, which is why fuel economy and recipe volumes differ significantly between American and British sources.
How many millilitres are in a cup, and which cup?
A US customary cup is 236.588 mL (one sixteenth of a US gallon). A US legal cup, used on nutrition labels, is exactly 240 mL. A UK imperial cup is 284 mL, though that unit is no longer formally recognised in British metrology. For most cooking, the 236.6 mL figure is used, and the 3.4 mL difference between it and the legal cup is negligible in practice.
Is a litre the same as a cubic decimetre?
Yes, by exact SI definition. The 16th General Conference on Weights and Measures (1964) confirmed that one litre equals exactly one cubic decimetre (0.001 cubic metres). Conversion between litres and cubic metres is therefore lossless. One millilitre also equals exactly one cubic centimetre, which is why cm3 and mL are interchangeable in science and cooking.
What is the difference between a US pint and a UK pint?
A US liquid pint is 473.176 mL, while a UK (imperial) pint is 568.261 mL, about 20 percent more. This matters most in beer and recipe contexts: ordering a pint in a British pub gives you more liquid than ordering one in an American bar, and British recipes specifying pints of milk will call for noticeably more liquid than a US pint would provide.
How many teaspoons are in a tablespoon, and how many tablespoons in a cup?
In the US system, 1 tablespoon = 3 teaspoons, and 1 US cup = 16 tablespoons = 48 teaspoons. A US tablespoon is 14.787 mL; a teaspoon is 4.929 mL. Some older UK recipes use a different tablespoon of about 17.7 mL, so when converting cooking quantities always confirm which system the recipe was written for.
Can I convert between volume and weight (mass) with this tool?
No. Volume and mass are different physical quantities, and converting between them requires knowing the density of the substance. For water at room temperature, 1 litre weighs almost exactly 1 kilogram, so the numbers coincide. But 1 litre of vegetable oil weighs about 0.92 kg, and 1 litre of honey about 1.42 kg. For density-based conversions, use a dedicated weight-from-volume calculator.