Volume Converter: Liters, Gallons, Cups and Fluid Ounces

The volume converter changes a value between fifteen units: milliliter (mL), liter (L), cubic centimeter (cm³), cubic meter (m³), cubic inch (in³), cubic foot (ft³), cup, US pint (pt), US quart (qt), US gallon (gal), US fluid ounce (fl oz), tablespoon (tbsp), teaspoon (tsp), imperial gallon (imp gal) and imperial pint (imp pt). Typing in either card updates the other card and the All Units list.

Updated 2026-09-30Reviewed by CalcX Editorial Team5 sources5 min read

What the volume converter does

The metric side is decimal and exact: 1 L = 1,000 mL = 1 dm³, 1 m³ = 1,000 L, and a cubic centimeter is the same size as a milliliter. The US units are exact subdivisions of one gallon: 1 gal = 4 qt = 8 pt = 16 cups = 128 fl oz, 1 cup = 8 fl oz, and 1 fl oz = 2 tbsp = 6 tsp. One US gallon is 231 in³ = 3.785411784 L. The imperial units stand apart: 1 imp gal = 4.54609 L and 1 imp pt = 568.26125 mL.

For length and mass use the length converter and the weight converter; for typed arithmetic, the scientific calculator.

How to use it

Choose the units.Each card has a dropdown of all fifteen units; the page opens with Milliliter on the left and Liter on the right.
Type the value.The card you last touched is the input side; the other side converts live. The swap button exchanges the units and carries the value across.
Type an expression if one number is not enough.The focused field evaluates it with the same engine as the scientific calculator: 3/4, 1+2 and 1/3 all work. A quiet hint shows the running value (= 0.75); invalid text (2+) shows = ? and keeps the last settled value converting.
Settle with Enter or `=`.The expression collapses to its value at 12 significant digits.
Read the All Units list.Below the cards the same quantity appears in every unit; click a row to move the input side to that unit.

Worked examples

A US gallon. Left card Gallon (US) (gal), right card Liter (L), type 1: the right field reads 3.785411784, and All Units shows Milliliter 3,785.411784, Cubic inch 231, Cup (US) 16, Pint (US) 8, Quart (US) 4, Fluid ounce (US) 128, Tablespoon 256, Teaspoon 768, and Gallon (UK) 0.8326741846. The 231 cubic inches are the definition: 231 × 16.387064 mL.
An imperial gallon is not a US gallon. Left card Gallon (UK) (imp gal), right card Liter (L), type 1: the right field reads 4.54609; the rows show Gallon (US) 1.2009499255, Pint (US) 9.607599404 and Pint (UK) 8.
Three quarters of a cup, in tablespoons. Left card Cup (US) (cup), right card Tablespoon (tbsp), type 3/4: the hint reads = 0.75, the right field reads 12, and the rows show Teaspoon 36, Fluid ounce (US) 6 and Milliliter 177.441177375. Press Enter and the left field settles to 0.75.

Background

In the SI the litre is exactly a cubic decimetre, so 1 L = 1,000 cm³ and a millilitre is a cubic centimetre; the cubic metre is the coherent unit and 1 m³ = 1,000 L. The US gallon is the older British wine gallon of 231 cubic inches, and the smaller US units are its subdivisions. Since 1959 one inch is exactly 25.4 mm, which makes 1 in³ = 16.387064 mL and a US gallon exactly 3.785411784 L. UK law defines the imperial gallon as 4.54609 dm³, divided into eight imperial pints of 20 imperial fluid ounces each (568.26125 mL); the converter offers the imperial gallon and pint but not the imperial fluid ounce.

Reading results and limits

Display rule.: Results carry up to 12 significant digits. Between 10⁻¹⁰ and 10¹⁵ they print with comma grouping and at most 10 decimal places (3,785.411784, 0.1774411774, 0.0000353147); at 10¹⁵ and above, and below 10⁻¹⁰, they switch to a six-decimal exponential form (1.000000e+15, 1.000000e-14); zero prints as 0; a result that overflows binary64, such as 1e308 cubic meters, prints ---.
Small values.: Values below 1 are capped at 10 decimal places, so the small end is where precision visibly drops: 1 mL in cubic feet reads 0.0000353147 and 1 mL in US gallons 0.0002641721. The last visible digit can round too — three teaspoons make one tablespoon exactly, 14.78676478125 mL, and the Milliliter row reads 14.7867647812.
Enter settles the input.: Enter settles the focused field to 12 significant digits without grouping, and the rows then convert that written number: while 1/3 in a cup is still live the Milliliter row reads 78.8627455, and after Enter it reads 78.8627454999.
Volume only.: It does not convert length or mass: dimensions live on the length converter and weights on the weight converter.

Common mistakes

"gal", "imp gal", "pt" and "imp pt" are four different units. A US gallon is 3.785411784 L, an imperial gallon 4.54609 L; 1 imp gal = 1.2009499255 US gal and 1 imp pt = 1.2009499255 US pt. Feeding a UK figure into "gal" understates it by about 17%, and a US figure into "imp gal" overstates it by about 20%.
The cup is the US customary cup, 236.5882365 mL. The US nutrition-label cup is 240 mL and the metric cup of Australia, Canada and New Zealand is 250 mL, 5.7% larger; a 250 mL measuring cup overshoots.
1/3 cup is not 5 tablespoons. The converter shows 1/3 cup = 5.3333333333 tbsp = 16 tsp, so writing 5 tbsp is 6.25% short.
Fluid ounces are volume, not weight. The fl oz row measures volume; ounces and grams belong to the weight converter.

Where it is used

Cooking and baking. Cups, tablespoons and teaspoons to millilitres: 3/4 cup is 12 tbsp, or 177.441177375 mL.
Fuel and drink labels. US and imperial gallons beside litres: 1 gal is 3.785411784 L and 1 imp gal is 4.54609 L.
Containers and shipping. Cubic metres to litres or cubic feet for freight and tank volumes: 1 m³ is 1,000 L.