Gallon Converter

What the Gallon Converter does

Gallon Converter: 1 gal = 3.785411784 L, so multiply a gallon (US) value by 3.785411784 to get litre, or divide to go back. Example: 1 gal = 3.785411784 L.

Point it at Value, From and To and it returns Result, How it was calculated and Reverse conversion. Results refresh instantly, so trying variations costs nothing but a moment.

Two industries often use the same word for slightly different quantities. That is usually what brings people following a recipe or spec written elsewhere here.

This runs client-side, which means we never receive what you enter and could not retrieve it if asked.

The sections that follow cover the fields, the method, and one full example computed from the defaults.

What do the Gallon Converter fields mean?

The Gallon Converter uses 3 inputs. Every field is populated on load; treat those numbers as a template rather than a suggestion.

How does the Gallon Converter work?

Both units are converted through volume's base unit (L), so any of the 19 units in the dropdowns can be paired in either direction without loss of accuracy.

Definitions are taken from the SI system where one exists, and from CODATA or the IAU where a unit is established by measurement. No factor is rounded before the calculation.

Worked example

These are the values the Gallon Converter loads by default, and the result it produces from them. This walkthrough uses the starting values, which means you can follow along without typing anything.

US and imperial gallons

There are two different gallons in common use, and they are genuinely different volumes, not just different names for the same thing: the US gallon is exactly 3.785411784 litres, while the UK imperial gallon is exactly 4.54609 litres, about 20% larger.

Worth knowing

• This split explains a persistent confusion in car fuel-economy figures: a car quoted at "40 mpg" in the UK is not as efficient as the same number would suggest if read as US mpg, precisely because the UK gallon holds 20% more fuel. The two "40 mpg" figures represent different actual efficiencies.
• The imperial gallon was historically defined as the volume of 10 pounds of water under specified conditions, while the US gallon derives from an older English wine-trade measure (the "Queen Anne gallon") that predates the imperial standard: they diverged because the US retained the older definition after independence while Britain standardised to a new one in 1824.
• Fuel pumps, milk containers and most retail packaging in the US use the US gallon; the UK largely moved to litres for retail sale (except fuel is still often discussed informally in terms of the old imperial gallon), always check which country’s gallon a figure refers to before converting.

Definitions: BIPM SI Brochure · NIST reference on units

How to use it

1. Enter Value.
2. Pick a value for From: the options are Millilitre (mL), Centilitre (cL), Litre (L), Cubic metre (m³), Cubic centimetre (cm³) or Cubic inch (in³).
3. Pick a value for To: the options are Millilitre (mL), Centilitre (cL), Litre (L), Cubic metre (m³), Cubic centimetre (cm³) or Cubic inch (in³).
4. The result appears as you type. There is no button to press.
5. You get Result, How it was calculated and Reverse conversion back.
6. Share the link rather than a screenshot. It carries the values with it.

What this tool does not do

• Repeated conversions compound rounding, so convert once from the original value where you can.
• Conversion factors use SI definitions; some industries use their own rounded factors.
• It does not account for anything you did not enter, by definition.
• Results are only as good as the inputs. Check your units before reading anything into the output.

Frequently asked questions

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