Convert gallons to millilitres

Content last reviewed:2026-09-30

A US gallon is 3,785.41 millilitres, an imperial gallon 4,546.09 and a US dry gallon 4,404.88. Type a number of gallons and the result appears at once. The Gallon type switch under the fields picks one of those three measures. A water cooler bottle of 5 US gal is 18,927.06 millilitres.

Gallons

US gal

Millilitres

Gallon type

US: 3.785 l, the gallon of American fuel prices and containers. UK: 4.546 l, the gallon behind British miles-per-gallon figures. US dry: 4.405 l, a former US grain measure, used until the 1990s.

How many millilitres are in a gallon?

One US gallon is 3,785.41 millilitres. Multiply the number of gallons by 3,785.411784: millilitres = gallons × 3,785.411784[1].

The same multiplier works for every other number of gallons. Two gallons come to 7,570.82 millilitres. Five gallons give 18,927.06 millilitres, the size of the bottle that sits on a water cooler[2]. Ten gallons work out at 37,854.12 millilitres, just under 38 litres. At that size the millilitre figure runs to five digits, so larger volumes are easier to read in litres.

Which gallon your number describes decides the result. An imperial gallon holds 4,546.09 millilitres, a fifth more[3]. A US dry gallon holds 4,404.88 millilitres and was used for grain until the 1990s[4]. The Gallon type switch under the fields sets the measure, and the multiplier changes with it.

For the other direction use the millilitres to gallons converter. For fuel prices and tank sizes the gallons to litres converter is the easier read.

What is a gallon, and what is a millilitre?

A gallon describes whole containers: jerrycans, buckets, bottles and drums. The US measure is exactly 231 cubic inches, and that definition gives 3,785.411784 millilitres[4]. British weights-and-measures law writes its own gallon straight into metric units, as 4.54609 cubic decimetres[3].

The millilitre comes from the litre, and the litre has had a single definition since 1964. The General Conference on Weights and Measures recorded then that the word litre may be used as a special name for the cubic decimetre[5]. A millilitre is a thousandth of that cube and takes up exactly one cubic centimetre[6].

That makes a millilitre easy to picture as a size: a container measuring 10 by 10 by 10 centimetres holds exactly 1,000 millilitres. An inch is exactly 2.54 centimetres, so a cube with one-inch sides holds 16.387064 millilitres. That is why the US gallon, defined in cubic inches, runs to six decimal places in millilitres.

A red steel fuel jerrycan embossed with the marking 20 L, standing on gravel — The can carries an embossed 20 L, which is 20,000 millilitres. On the US measure that comes to 5.283441 gallons. Photo: Egor Myznik, Unsplash.

Gallons to millilitres conversion table

The three columns match the three options on the Gallon type switch. The same number of gallons gives three different volumes, and the imperial column runs a fifth higher than the US one.

Gallons	US gallon	Imperial gallon	US dry gallon
0.2 gal	757.08 ml	909.22 ml	880.98 ml
0.25 gal	946.35 ml	1,136.52 ml	1,101.22 ml
0.3 gal	1,135.62 ml	1,363.83 ml	1,321.47 ml
0.5 gal	1,892.71 ml	2,273.05 ml	2,202.44 ml
0.6 gal	2,271.25 ml	2,727.65 ml	2,642.93 ml
0.75 gal	2,839.06 ml	3,409.57 ml	3,303.66 ml
1 gal	3,785.41 ml	4,546.09 ml	4,404.88 ml
1.25 gal	4,731.76 ml	5,682.61 ml	5,506.10 ml
1.3 gal	4,921.04 ml	5,909.92 ml	5,726.35 ml
1.5 gal	5,678.12 ml	6,819.14 ml	6,607.33 ml
2 gal	7,570.82 ml	9,092.18 ml	8,809.77 ml
2.5 gal	9,463.53 ml	11,365.23 ml	11,012.21 ml
3 gal	11,356.24 ml	13,638.27 ml	13,214.65 ml
3.5 gal	13,248.94 ml	15,911.32 ml	15,417.09 ml
4 gal	15,141.65 ml	18,184.36 ml	17,619.54 ml
4.5 gal	17,034.35 ml	20,457.41 ml	19,821.98 ml
5 gal	18,927.06 ml	22,730.45 ml	22,024.42 ml
6 gal	22,712.47 ml	27,276.54 ml	26,429.30 ml
7 gal	26,497.88 ml	31,822.63 ml	30,834.19 ml
8 gal	30,283.29 ml	36,368.72 ml	35,239.07 ml
9 gal	34,068.71 ml	40,914.81 ml	39,643.95 ml
10 gal	37,854.12 ml	45,460.90 ml	44,048.84 ml
15 gal	56,781.18 ml	68,191.35 ml	66,073.26 ml
20 gal	75,708.24 ml	90,921.80 ml	88,097.68 ml
25 gal	94,635.29 ml	113,652.25 ml	110,122.09 ml
30 gal	113,562.35 ml	136,382.70 ml	132,146.51 ml
40 gal	151,416.47 ml	181,843.60 ml	176,195.35 ml
50 gal	189,270.59 ml	227,304.50 ml	220,244.19 ml
55 gal	208,197.65 ml	250,034.95 ml	242,268.61 ml
100 gal	378,541.18 ml	454,609.00 ml	440,488.38 ml

Have a figure in millilitres and want gallons? Go to the millilitres to gallons converter.

How many millilitres the containers quoted in gallons hold

A US catalogue gives the capacity of equipment in gallons, while a metric specification for the same object gives litres. Both figures stand side by side here.

Capacity from the catalogue	Millilitres	Litres	What the container is
3 gal	11,356.24 ml	11.36 l	Water cooler bottle, one of the original sizes
5 gal	18,927.06 ml	18.93 l	Water cooler bottle, the standard size today
5.17 gal	19,570.58 ml	19.57 l	Sixth-barrel keg, known as a torpedo keg
6 gal	22,712.47 ml	22.71 l	Water cooler bottle, one of the original sizes
7.75 gal	29,336.94 ml	29.34 l	Quarter-barrel keg, known as a pony keg
15.5 gal	58,673.88 ml	58.67 l	Half-barrel keg, the standard US beer keg
55 gal	208,197.65 ml	208.20 l	Steel drum under its American name

Bottle sizes come from the article on water coolers[2], keg capacities from the article on kegs[7].

The three gallons and the number of 750 ml bottles each holds

The rows match the options on the Gallon type switch. The second column says how many standard wine bottles fill one gallon of each measure.

Gallon type	Millilitres	750 ml bottles	Where you meet it	Option on the switch
US liquid	3,785.41 ml	5.05	Fuel, water cooler bottles, kegs and drums in the United States	US
Imperial	4,546.09 ml	6.06	UK fuel-economy figures and British weights-and-measures law	UK / Imperial
US dry	4,404.88 ml	5.87	A former US grain measure, an eighth of a bushel	US dry

The US and imperial figures come from the NIST table[1], the dry gallon and its use for grain from the article on the gallon[4].

Which number formats does this converter handle?

The field accepts each of these formats and converts it, so you don’t need to tidy a number before you paste it. The table shows what the converter does with each one, and the converter worked out the results itself.

What you type	What the converter shows	How we read it
2.5	9463.53 ml	The point is the decimal separator, so this is two and a half gallons.
2,5	9463.53 ml	A comma followed by one digit is a European decimal comma, so we read it as two and a half.
1,500	5678117.68 ml	Three digits after the comma mark a thousands separator, so we count one thousand five hundred gallons. A note under the field says: Read as 1500. If you meant 1.5, type 1.5.
1 500	5678117.68 ml	A space between the thousands is skipped, so this is one thousand five hundred gallons as well.
3/4	2839.06 ml	We convert a fraction with a slash directly, so it doesn’t need to become 0.75 first.
1½	5678.12 ml	A ½ character copied from a recipe or a label is added to the number in front of it.
5 gal	18927.06 ml	A unit pasted along with the number doesn’t get in the way, so we count five gallons.
1 UK gal	4546.09 ml	The field reads UK gal as the British imperial gallon and counts it as 4,546.09 millilitres.

How do you convert gallons to millilitres?

The whole calculation is one multiplication. The steps show how to match the multiplier to the measure in front of you.

Check where the number of gallons comes from
A US catalogue, an owner’s manual and a label from the States all describe the liquid gallon. British paperwork and fuel-economy figures from a British test describe the imperial gallon.
Set that measure on the Gallon type switch
The switch sits under both fields and offers three buttons: US, UK / Imperial and US dry. The line under them gives the capacity of each gallon in litres, so the choice is visible before you type anything.
Type the number of gallons
The result appears as you type. The field takes a point or a comma, and a slash for fractions, so 2 1/2 gives the same answer as 2.5.
Read the millilitres and take them further
The Copy result button puts the number on the clipboard. For larger volumes divide it by a thousand to get litres: 18,927.06 millilitres is 18.93 litres.

The same drum: 55 gallons in the States, 44 in Britain

A steel drum filled to about 200 litres carries two different names. In the United States it is called a 55-gallon drum, and in Britain and the rest of the world a 44-gallon drum[8].

Both names describe the same object, because each counts in a different gallon. Forty-four imperial gallons come to 200,027.96 millilitres, almost exactly the 200 litres the drum is filled to. Fifty-five US gallons are 208,197.65 millilitres. The gap between the two figures is 8,169.69 millilitres.

Open steel drums photographed from above, in black and white — A steel drum has a nominal capacity of 200 litres, or 200,000 millilitres. That comes to 52.834 US gallons or 43.994 imperial gallons. Photo: Albert Stoynov, Unsplash.

Convert other units to Millilitres

oz to ml liters to ml deciliters to ml centiliters to milliliters cups to ml tbsp to ml tsp to ml drops to ml quarts to ml pints to ml

Convert Gallons to other units

gallons to liters gallons to barrels gallons to cups gallons to pints

Sources

NIST Special Publication 811, appendix B.9 — conversion factors — National Institute of Standards and Technology
Water cooler — Wikipedia
Weights and Measures Act 1985, Schedule 1 — legislation.gov.uk
Gallon — Wikipedia
Resolution 6 of the 12th CGPM (1964) on the litre — Bureau International des Poids et Mesures
Litre — Wikipedia
Keg — Wikipedia
Drum (container) — Wikipedia

Every figure in the tables was computed from the unit definitions and checked arithmetically before publication. Historical values and the names of local units come from the sources listed above.

Content last reviewed: September 30, 2026 · written and checked by the Arteon team

Frequently asked questions about gallons and millilitres

How many fluid ounces are in a gallon?

A US gallon holds exactly 128 fluid ounces, so one ounce is 29.57 millilitres. An imperial gallon divides into 160 imperial ounces of 28.41 millilitres. Where the number 128 comes from is explained by the ounces to cups converter.

Is a one-litre bottle a quarter of a gallon?

Almost. One thousand millilitres is 0.264172 of a US gallon, a little over a quarter. On the imperial setting it gives 0.219969, and on the US dry setting 0.227021.

Arteon free tool screenshot: Convert gallons to millilitres

A question or a suggestion?

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