Volume Conversion Calculator
Enter a volume and pick your starting unit. The calculator converts it to every other common unit at once, covering metric (liters, milliliters, cubic meters), US customary (gallons, fluid ounces, cups, pints, quarts, cubic feet), UK imperial, and specialty units including oil barrels and dry measures. Results update as you type, and the steps panel shows the exact conversion factor used.
How volume conversion works
Every volume conversion passes through a common base unit. This calculator uses the liter as the bridge: to convert from any unit A to any unit B, it first multiplies by the factor that turns A into liters, then divides by the factor that turns liters into B. For example, to convert US gallons to UK pints, the calculator converts to liters (1 US gal = 3.78541 L) and then to UK pints (1 UK pt = 0.568261 L), giving 3.78541 / 0.568261 = 6.661 UK pints per US gallon. This two-step approach means only one table of factors is needed to support hundreds of unit pairs.
US customary vs UK imperial units
The most common source of confusion in volume conversion is the difference between US and UK units that share the same name. A US fluid ounce is 29.574 mL; a UK fluid ounce is 28.413 mL, about 4% smaller. A US gallon is 3.785 liters; a UK (imperial) gallon is 4.546 liters, about 20% larger. This means a recipe calling for "1 pint of milk" means 473 mL in a US kitchen and 568 mL in a UK kitchen. Fuel economy figures such as miles per gallon are also not directly comparable between countries without conversion. Always check whether a source uses US or UK units before applying a conversion.
Metric volume units and their relationships
The metric system is built on powers of ten, which makes conversions straightforward. The base unit is the cubic meter (m³), but the liter (L), defined as exactly one cubic decimeter (1 dm³ = 0.001 m³), is the practical everyday unit. Standard prefixes apply: 1 kiloliter (kL) = 1000 L, 1 deciliter (dL) = 0.1 L, 1 centiliter (cL) = 0.01 L, 1 milliliter (mL) = 0.001 L. One milliliter equals one cubic centimeter (1 mL = 1 cm³), a useful identity in medicine and chemistry. Scientific contexts favor m³ and cm³ to keep units consistent with the International System of Units (SI).
Practical applications by field
Cooking and baking rely on cups, tablespoons, teaspoons, and fluid ounces; converting between US and metric recipes is the most common everyday use. Medicine and pharmacy use milliliters almost exclusively for liquid doses, while intravenous drip rates use mL per hour or mL per minute. The petroleum and energy industry measures crude oil in barrels (1 oil barrel = 42 US gallons = 158.987 L); natural gas volumes are quoted in cubic feet or cubic meters. Civil engineering and hydrology work in cubic meters, cubic feet, and acre-feet (1 acre-foot = about 1233.5 m³). Aquariums and swimming pools are sized in gallons or liters. Knowing which system a source document uses before converting prevents costly errors in all of these contexts.
Common volume unit conversion factors
| Unit | Symbol | Liters (exact / rounded) | System |
|---|---|---|---|
| Milliliter | mL | 0.001 | Metric |
| Centiliter | cL | 0.01 | Metric |
| Deciliter | dL | 0.1 | Metric |
| Liter | L | 1 | Metric |
| Cubic centimeter | cm³ | 0.001 | Metric |
| Cubic meter | m³ | 1000 | Metric |
| US fluid ounce | fl oz | 0.029574 | US Customary |
| US cup | cup | 0.24 | US Customary |
| US pint | pt | 0.473176 | US Customary |
| US quart | qt | 0.946353 | US Customary |
| US gallon | gal | 3.785412 | US Customary |
| Cubic inch | in³ | 0.016387 | US Customary |
| Cubic foot | ft³ | 28.3168 | US Customary |
| UK fluid ounce | fl oz | 0.028413 | Imperial |
| UK pint | pt | 0.568261 | Imperial |
| UK gallon | gal | 4.54609 | Imperial |
| US liquid barrel | bbl | 119.240 | US Customary |
| Oil barrel | bbl | 158.987 | Petroleum |
Exact or rounded conversion factors. All factors convert the listed unit to liters (the SI derived unit for volume).
Frequently asked questions
How many liters are in a US gallon?
Exactly 3.785411784 liters. For quick mental arithmetic, the approximation 3.785 L per US gallon is accurate to within 0.01%. A US gallon contains 4 quarts, 8 pints, 16 cups, or 128 fluid ounces.
What is the difference between a US gallon and a UK gallon?
A US liquid gallon is 3.785 liters. A UK (imperial) gallon is 4.546 liters, making it about 20% larger. A US pint is 473 mL; a UK pint is 568 mL. A US fluid ounce is 29.57 mL; a UK fluid ounce is 28.41 mL. These differences affect recipes, fuel economy figures, and any measurement described as "gallons" or "pints" without a country qualifier.
How do I convert milliliters to teaspoons?
Divide milliliters by 4.929 to get US teaspoons, or by 5.919 to get UK teaspoons. A US teaspoon is 4.929 mL; a UK teaspoon is 5.919 mL. A practical rule for the US: 5 mL is very close to 1 US teaspoon, accurate to within 1.4%. Many medical dosing spoons are calibrated to exactly 5 mL.
How many cups are in a liter?
About 4.167 US cups (since 1 US cup = 240 mL = 0.24 L). A metric cup is exactly 250 mL, so 1 liter = exactly 4 metric cups. A UK cup is 284 mL, giving about 3.52 UK cups per liter. Always check which cup size a recipe uses before scaling.
What is an oil barrel in liters and gallons?
One oil barrel (petroleum barrel, abbreviated bbl) equals exactly 42 US gallons, or 158.987 liters. This unit is used for crude oil, refined products, and OPEC production quotas. It differs from a US liquid barrel, which is 31.5 US gallons (119.24 L) and is used for beer and other liquids in trade.
How do I convert cubic feet to gallons?
Multiply cubic feet by 7.4805 to get US gallons, or by 6.2288 to get UK gallons. For example, a 10-cubic-foot fish tank holds about 74.8 US gallons. To go the other way, divide US gallons by 7.4805 to get cubic feet.