Convert gallon (UK / imperial) to gallon (US).

Convert gallon (UK / imperial) (gal-uk) to gallon (US) (gal-us). This is a fixed-ratio conversion — multiply the input by the factor below.

Formula

gal-us = gal-uk × 1.20095

Reference values

Things to watch for

• US and UK gallons are different. 1 US gal = 3.785 L; 1 UK (imperial) gal = 4.546 L. Recipes from the UK will not work with US cups.
• Volume scales as the cube of length: doubling a container's dimensions multiplies volume by 8, not 2.
• For viscous or compressible fluids, volume changes with temperature and pressure. Specify conditions for precise work.

What is a UK (imperial) gallon?

One imperial gallon equals exactly 4.54609 liters — about 20% more than a US gallon. Fuel economy in the UK (miles per gallon), historical British recipes, and some Commonwealth countries.

What is a US gallon?

One US gallon equals exactly 3.785411784 liters or 128 US fluid ounces. Gasoline, milk, paint, and most US liquid measurement.

Real-world examples of imp gal

These anchors can be useful when sizing up a value. 1 imp gal is about a typical kettle's capacity; 5 imp gal is a standard UK bucket.

How to convert UK (imperial) gallon to US gallon

To convert a value from UK (imperial) gallon (gal (UK)) to US gallon (gal (US)), apply the conversion factor shown in the formula above. The calculation is the same whether you do it by hand, in a spreadsheet, or with the live converter on this page.

Steps:

1. Take your input value in gal (UK).
2. Apply the formula gal-us = gal-uk × 1.20095.
3. The result is your value in gal (US).

For repeated calculations, save the formula in a spreadsheet or use the live converter at the top of this page — it handles the math automatically and displays the result as you type.

Frequently asked questions

How do I convert gal (UK) to gal (US)?

Apply the formula gal (UK) → gal (US) shown above, or just type your value into the converter at the top of this page. The result updates instantly.

Which is bigger, gal (UK) or gal (US)?

This depends on the conversion ratio in the formula. If the factor multiplied by your value gives a larger number, then gal (US) is the smaller unit (so it takes more of them to express the same quantity). If the result is smaller, then gal (US) is the larger unit.

When would I use gal (UK) versus gal (US)?

Both units measure volume, so the choice depends on context. Uk (imperial) gallon is typically used for cooking, beverages, fuel, and industrial fluid handling; US gallon similarly. Most professional fields standardize on one or the other based on regional conventions or technical tradition.

How precise is this gal (UK) to gal (US) conversion?

The conversion factor shown is the internationally defined exact value (or the best-published approximation if the relationship is irrational, like degrees-to-radians). The live converter on this page uses double-precision floating-point math, accurate to about 15 significant digits — far beyond any practical engineering need.

Is the conversion ratio exact, or an approximation?

Most unit conversions between SI metric units, and between SI and US customary units, have been formally defined as exact values since the 1959 international yard-pound agreement and subsequent SI redefinitions. Exceptions are unit pairs that involve irrational numbers (radians, e.g.) or empirical conversions (like food calories, which depend on temperature). When in doubt, consult the formula at the top of this page.

Related conversions

See also