About the Volume Converter

The volume converter translates between eleven units of volume: millilitre, litre, cubic metre, cubic centimetre, cubic inch, cubic foot, US cup, US pint, US quart, US gallon, and UK gallon. All conversions are expressed in millilitres as the pivot unit, which equals one cubic centimetre and one-thousandth of a litre.

The litre was originally defined in 1795 as one cubic decimetre, but was redefined in 1901 as the volume of one kilogram of water at 4°C (its temperature of maximum density). This introduced a small discrepancy because the kilogram prototype was slightly too heavy. In 1964 the 12th CGPM restored the original definition: 1 litre = 1 cubic decimetre = exactly 1000 cubic centimetres = exactly 1000 millilitres.

The US liquid gallon is defined as exactly 231 cubic inches, which equals approximately 3.78541 litres. The UK (imperial) gallon was defined in 1824 as the volume of 10 pounds of water at 62°F, which equals approximately 4.54609 litres. The US and UK gallons are not the same: 1 UK gallon equals about 1.20095 US gallons.

The converter handles any real input, including negatives (which can arise in signed-volume calculations in fluid dynamics) and zero. The US pint, quart, and cup are related by factors of 2: 2 cups = 1 pint, 2 pints = 1 quart, 4 quarts = 1 gallon. The UK versions are slightly different and not included in the dropdown.

How It Works

The converter uses the two-step method through millilitres:

base_in_ml = value * factor[from]
result = base_in_ml / factor[to]

The factor table (in ml) is:

ml  = 1 ml             L  = 1000 ml          m³ = 1,000,000 ml
cm³ = 1 ml             in³ = 16.3871 ml       ft³ = 28,316.8 ml
cup = 236.588 ml       pt  = 473.176 ml        qt  = 946.353 ml
gal (US) = 3,785.41 ml  galUK = 4,546.09 ml

The metric factors are exact: 1 L = 1000 ml exactly, 1 m³ = 1000 L exactly, 1 cm³ = 1 ml exactly. The imperial factors are derived from the underlying length definitions: 1 in³ = (2.54 cm)³ = 16.387064 cm³ = 16.387064 ml, displayed as 16.3871 for readability.

The US liquid measurements are defined exactly in terms of the cubic inch: 1 US gallon = 231 in³, 1 US quart = 1/4 gallon, 1 US pint = 1/8 gallon, 1 US cup = 1/16 gallon. The UK gallon is defined separately as approximately 4546.09 ml.

The two-step method through millilitres keeps the code simple and makes the conversions transparent. The choice of millilitres (rather than litres or cubic metres) as the pivot matches the magnitudes of everyday cooking measurements.

Worked Examples

Converting 1 US gallon to litres: the input in ml is 3785.41 ml, and the result is 3785.41 / 1000 = 3.78541 L. The popular approximation "1 US gallon is about 3.8 litres" is therefore accurate to within 0.4 percent.

Converting 1 UK gallon to US gallons: the input in ml is 4546.09 ml, and the result is 4546.09 / 3785.41 = 1.20095 US gallons. This explains why a UK fuel economy figure (miles per imperial gallon) is not directly comparable to a US figure: the UK gallon is about 20% larger.

Converting 1 cubic foot to litres: the input in ml is 28,316.8 ml, and the result is 28.3168 L. This is the volume of a cube 1 foot on each side, which is approximately 28.3 litres. A typical refrigerator has an internal volume of about 20 cubic feet, or about 566 litres.

When to Use This Tool

Use the volume converter when you need to:

Convert cooking measurements between cups, millilitres, and fluid ounces.
Translate fuel tank capacities between US gallons, UK gallons, and litres.
Convert engine displacement between cubic inches and litres (a 350 cubic-inch engine is 5.7 L).
Compute the volume of a shipping container in cubic metres from cubic feet.
Convert aquarium or pool volumes between gallons and litres.
Translate recipe quantities between US and UK measurements.
Compute the volume of a liquid in a tank from its dimensions in different units.

Limitations & Disclaimer

This converter uses exact conversion factors for metric units and US/UK liquid measurements defined in SI. It does not handle US dry measurements (dry pint, dry quart, dry gallon), fluid ounces, tablespoons, or teaspoons. The "gallon" options refer to US and UK liquid gallons only. Results are subject to IEEE 754 floating-point precision. See our disclaimer for full details.

Frequently Asked Questions

Why are US and UK gallons different?

The US gallon was defined in 1707 as exactly 231 cubic inches (about 3.785 L), based on the British wine gallon. The UK imperial gallon was defined in 1824 as the volume of 10 pounds of water at 62°F (about 4.546 L). They diverged because the UK redefined its gallon after US independence, while the US kept the older British measure.

What is the difference between a fluid ounce and a weight ounce?

A fluid ounce is a unit of volume (about 29.5735 ml in the US), while a weight ounce is a unit of mass (about 28.3495 g). The two are not the same and are not interchangeable. The confusion arises because both are called 'ounces' in everyday speech.

Is 1 millilitre the same as 1 cubic centimetre?

Yes. Since 1964, the litre has been defined as exactly 1 cubic decimetre (= 1000 cubic centimetres), so 1 millilitre equals exactly 1 cubic centimetre. The medical field uses 'cc' (cubic centimetre) and 'ml' interchangeably for syringe measurements.

Why is the litre not an SI unit?

Although the litre is not an SI base or derived unit, it is accepted for use with SI per the SI Brochure 9th edition, Table 6. The SI derived unit of volume is the cubic metre, but the litre is more convenient for everyday quantities because 1 cubic metre equals 1000 litres, which is a large volume.

How many cups are in a pint or quart?

In the US liquid system: 2 cups = 1 pint, 2 pints = 1 quart, 4 quarts = 1 gallon. So 1 US gallon = 16 cups. In the UK, the relationships are similar but the absolute sizes are different: 1 UK pint = 568.261 ml, while 1 US pint = 473.176 ml.

Does the converter handle dry measurements?

No. The US dry gallon, dry pint, and dry quart are slightly larger than their liquid counterparts and are used for measuring dry bulk goods like grain. This converter handles only liquid measurements and the cubic units. For dry measurements, use a dedicated dry-volume converter.

Last updated: September 9, 2026 · Author: HT99 Tools Editorial Team