OTHER · VOLUME CONVERTER
Volume Converter Calculator
Convert between US and imperial (UK) volume units. Includes gallons, pints, quarts, fluid ounces, cups, and litres. US and imperial units are clearly separated to prevent errors.
About This Calculator
Convert volume between US customary and UK imperial units. US and imperial volumes diverge significantly at the gallon level (US gallon = 3.785 L; imperial gallon = 4.546 L — a ~20% difference). Use the system toggle to switch between US and imperial unit sets.
How It Works
Choose US customary or Imperial (UK) as your unit system, then select your from and to units. All conversions use the litre as a canonical base and apply exact factors from NIST SP 811 and the UK Weights and Measures Act 1985.
The Formula
1 US gallon = 3.785411784 L (exact, US definition). 1 imperial gallon = 4.54609 L (exact, UK Weights and Measures Act 1985). US and imperial pints, quarts, and fluid ounces are all different — never treat them as interchangeable.
Frequently Asked Questions
- Is a US gallon the same as a UK gallon?
- No. A US gallon is exactly 3.785411784 litres; a UK imperial gallon is exactly 4.54609 litres — about 20% larger. Always specify which gallon you mean.
- Why is there no "cup" in the imperial system?
- There is no standardised imperial cup. The cup measure is specific to US customary units (1 US cup = 8 US fl oz = 236.6 mL).
- What is a fluid ounce?
- A US fluid ounce (US fl oz) = 29.5735 mL. A UK imperial fluid ounce (UK fl oz) = 28.4131 mL. They differ by about 4%.