Are US and imperial gallons the same size?

No: an imperial gallon holds about 20% more. FluffyBench's Volume Converter turns liters, milliliters, cubic meters and both kinds of gallon into each other as you type, so pick the gallon your recipe or label names.

FluffyBench · 5 min read · Reviewed October 15, 2026

How it works

Pick the unit you have under From
Pick the unit you need under To
Type the number in Input value
Read or copy the answer

Volume units

Cubic meter (m³), Liter (L), Milliliter (mL), US liquid gallon (gal), Imperial gallon (gal). Cups and fluid ounces aren't on the list.

Two gallons

US liquid and imperial gallons are separate choices, so a gallon figure converts at the size its source meant.

Every unit at once

Below the answer, your volume also appears in each other unit, with its own Copy button.

Limits It converts a number you already have; it can't check a jug's markings.

Changing units keeps the volume the same

Think of a measuring jug marked in milliliters on one side and liters on the other. The water stays put; FluffyBench's From and To only choose which marks you read.

One jug filled to a single waterline. The left scale reads 750 mL at the waterline and the right scale reads 0.75 L, with marks at 0, 250, 500, 750 and 1,000 mL beside 0, 0.25, 0.5, 0.75 and 1 L. — A smaller unit takes a bigger number for the same amount: 1,000 mL make 1 L. How we measured

US liquid and imperial gallons hold different amounts

Both are called a gallon, but they hold different amounts. Stand them side by side on one liter scale and the imperial gallon comes out about 20% bigger.

Two full vessels on a shared scale from 0 to 5 liters: a US liquid gallon holds 3.785411784 L and an imperial gallon holds 4.54609 L. — Check the full gallon name in your source before you convert. The US dry gallon is a third size, and FluffyBench doesn't offer it.

Converting imperial gallons to US gallons in FluffyBench

Here's 1 imperial gallon turned into US liquid gallons, from picking the units to copying the answer.

Step 1. Open From and pick the unit your amount is in. The two gallons are separate choices; picking one closes the list.
1. Choose Imperial gallon for a UK gallon.
2. US liquid gallon is the other, smaller gallon.
Step 2. To already reads US liquid gallon here. Open it the same way when you need liters, milliliters or cubic meters.
1. From reads Imperial gallon, the unit you have.
2. To reads US liquid gallon, the unit you need.
Step 3. Type the number alone, without gal; there's no Convert button to press.
1. Type 1 in Input value.
2. The number is in imperial gallons.
3. Example fills in 1 for a quick try.
Step 4. The answer updates as you type. The list below repeats your volume in every other unit.
1. Read 1.2009499255049 US liquid gallons.
2. Press Copy to put the number on your clipboard.
3. The same volume in liters: 4.54609.

Copy puts the number on your clipboard by itself, without the unit and without the commas the page shows in big numbers. Type the unit after you paste, and keep the “US” so nobody reads it as an imperial gallon.

A real FluffyBench result reads 1.2009499255049 US liquid gallons. The clipboard text is 1.2009499255049. An illustrated note shows 1.2009499255049 followed by US gal, which the reader typed. — Pasting into a field that's already labeled US gal? Then the number alone is right.

What does Swap do to the number you typed?

The arrows between From and To swap the two units, but Input value keeps the 1 you typed. After a swap, that 1 means a US liquid gallon, so the answer changes to 0.83267418462899 imperial gallons.

From Imperial gallon, To US liquid gallon: Input value is 1, in imperial gallons, and the result is 1.2009499255049 US liquid gallons. — Going back the other way? The After Swap setup is the one to use: type your US gallon figure in its Input value.

From US liquid gallon, To Imperial gallon: Input value is still 1, now in US liquid gallons, and the result is 0.83267418462899 imperial gallons. — Going back the other way? The After Swap setup is the one to use: type your US gallon figure in its Input value.

Common volume conversions

Need a rough figure without typing? Each row gives 1 of a unit in all the others.

Input	m³	L	mL	US gal	imp gal	Precision
1 m³	1	1,000	1,000,000	≈ 264.172	≈ 219.969	Values marked ≈ are rounded reference results.
1 L	0.001	1	1,000	≈ 0.264172	≈ 0.219969	Values marked ≈ are rounded reference results.
1 mL	10⁻⁶	0.001	1	≈ 0.000264172	≈ 0.000219969	Values marked ≈ are rounded reference results.
1 US gal	0.003785411784	3.785411784	3,785.411784	1	≈ 0.832674	Values marked ≈ are rounded reference results.
1 imp gal	0.00454609	4.54609	4,546.09	≈ 1.20095	1	Values marked ≈ are rounded reference results.

Values marked ≈ are rounded here; FluffyBench shows up to 14 significant digits.

No answer, or Copy unavailable?

Input value takes a number by itself; the unit belongs in From. If your browser blocks the clipboard, FluffyBench leaves the result ready to select.

Input value contains 1 gal. FluffyBench shows Enter a decimal number for Value. — Delete the unit text to clear the first message. For the second, select the number and copy it yourself.

The result 1.2009499255049 is selected above the message Copy was unavailable. Select and copy the result. — Delete the unit text to clear the first message. For the second, select the number and copy it yourself.

Converting a weight, an area or an oven temperature instead?

FluffyBench's Volume Converter works only with the five volume units above. A weight in grams or pounds, a floor area, or the oven temperature from the same recipe each has its own FluffyBench converter, so pick the one that matches your number.

How we measured

Date: October 15, 2026. Browser: The displayed controls were checked in Google Chrome 155.0.8059.40. Device: 32 logical processors.

Volume conversion multiplies the input by the source unit's SI factor divided by the target unit's SI factor. For example, 1 US gal = 3.785411784 L exactly.

Volume results use up to 14 significant digits, with trailing zeros removed and thousands grouped on the page. An exact unit definition can still produce a rounded decimal result.

Volume choices: Cubic meter (m³), Liter (L), Milliliter (mL), US liquid gallon (US gal), Imperial gallon (imp gal).

US liquid and imperial gallons have separate factors; changing the From gallon choice keeps the entered number and changes the capacity it represents.

Volume inputs accept decimal and exponent notation. Non-finite numbers and nonzero inputs that become zero in browser arithmetic are rejected. A conversion that overflows or turns a nonzero value into zero reports a numeric-range error.

The volume converter updates as you type, in this page, without a conversion request.

Cubic meter (m³): 1,000 L exactly. Liter (L): One cubic decimeter, a thousandth of a cubic meter. Milliliter (mL): 0.001 L exactly. US liquid gallon (US gal): 3.785411784 L exactly. Imperial gallon (imp gal): 4.54609 L exactly. The US liquid gallon, defined as 231 cubic inches, and the imperial gallon are different units, and the imperial gallon is about 20% larger. Check which one a figure uses before converting it. The US dry gallon is a third unit and is not offered here. A liter is a cubic decimeter, so 1,000 liters make a cubic meter and a milliliter equals a cubic centimeter.

The walkthrough, Swap and message screenshots show the live tool after choosing Imperial gallon under From and typing 1; Swap gave 0.83267418462899 imperial gallons for 1 US liquid gallon. The jug and gallon diagrams are drawn from the unit definitions, and the pasted note is an illustration.

Copy writes the plain result, such as 1.2009499255049, with no unit and no thousands commas.

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