Our Volume Unit Converter handles metric and US/Imperial volume units in a single tool. Enter any value and choose the units you want to convert between — mL, L, m³, cm³, US gal, UK gal, US cup, US pint, US quart, US fl oz, UK fl oz, US tablespoon, US teaspoon, cubic feet, cubic inches, or oil barrels. Every conversion runs through litres as the common base so results stay consistent across all unit pairs. Use it for cooking recipes (cup ↔ mL, tbsp ↔ tsp), home-improvement projects (cubic feet ↔ gallons), engineering (m³ ↔ L), or crude-oil math (barrel ↔ litre). Common equivalents are displayed in a grid below the primary result so you can cross-check a single value against ten other units at a glance.
Choose the unit you're converting from — millilitres, litres, cubic metres, US/UK gallons, cups, pints, quarts, fluid ounces, tablespoons, teaspoons, cubic feet/inches, or oil barrels.
Choose the unit you want the answer in. Swap units anytime with the swap button.
Type any number. The primary result updates instantly, with full-precision decimals.
Below the primary result, a grid shows the same value converted to every other supported unit, so you can cross-check at a glance.
Every volume unit is converted through litres (L) as the base. The input value is multiplied by the FROM factor to get litres, then divided by the TO factor to produce the result. Keeping a single base unit makes the math internally consistent and reversible for any unit pair.
litres = value × factor(from) | result = litres / factor(to)
1 US gallon = 3.78541 L, 1 UK (imperial) gallon = 4.54609 L — they are NOT the same, the UK gallon is ~20% bigger
US liquid ounce ≠ UK fluid ounce — US = 29.5735 mL, UK = 28.4131 mL (the UK one is smaller)
Kitchen shortcut: 1 US cup = 16 tablespoons = 48 teaspoons = 240 mL
1 litre = 1,000 cm³ = 1,000 mL — this is an exact definition, unlike most imperial conversions
1 oil barrel (bbl, petroleum) = 42 US gallons = 158.987 L — used in crude oil pricing
1 cubic foot = 7.48052 US gallons ≈ 28.3168 L — useful for tank and aquarium sizing
A wine bottle (750 mL) is about 25.36 US fl oz or just over 3 US cups
Volume measurement is complicated by the coexistence of three major systems: metric (liters and milliliters), US customary (gallons, quarts, cups, fluid ounces), and imperial (which shares names with US units but differs in size). A US gallon equals 3.785 liters, while an imperial gallon is 4.546 liters — nearly 20% larger. Even within the US system, a "cup" varies by context: a US legal cup (used in nutrition labeling) is 240 mL, while a US customary cup is 236.588 mL. In cooking, these small differences rarely matter, but in chemistry, pharmacy, and industrial applications, precision is critical. The metric system's decimal structure makes conversion straightforward (1 liter = 1,000 mL = 0.001 cubic meters), while converting between US customary units requires memorizing that 1 gallon = 4 quarts = 8 pints = 16 cups = 128 fluid ounces. Scientific and engineering applications use cubic meters (m³) as the SI standard, with cubic centimeters (cm³, identical to mL) common in medicine and automotive contexts (engine displacement). International recipes, pharmaceutical dosing, and global trade all require reliable volume conversion to avoid potentially costly or dangerous measurement errors.
Our converter keeps US and UK units clearly labelled so you never mix them up accidentally.
The most-searched cooking conversions:
1 US fl oz = 29.5735 mL, so an 8 oz glass = 236.6 mL.
For metric recipes:
To convert any volume, first multiply your value by the FROM unit's factor in liters, then divide by the TO unit's factor: result = (value × factor_from) ÷ factor_to.
For example, 2 US gallons to liters = 2 × 3.78541 = 7.57082 L.
The liter is defined by the International System of Units (SI) via the cubic meter, where 1 L = 1 dm³ = 0.001 m³ exactly, as documented by the BIPM.
Because every unit is anchored to this SI base, the math stays reversible and internally consistent. NIST publishes the customary-to-metric factors used here, so 1 US gallon = 3.785411784 L is exact by definition, not an approximation.
1 US liquid gallon = 3.78541 liters, while 1 UK (imperial) gallon = 4.54609 liters — the imperial gallon is roughly 20% larger.
The difference exists because the US gallon derives from the old English wine gallon (231 cubic inches) whereas the imperial gallon was redefined by the UK in 1824. NIST fixes the US gallon at exactly 3.785411784 L, and the imperial gallon is defined as exactly 4.54609 L.
This gap matters for fuel economy, brewing, and international recipes: a car rated at 40 UK mpg is only about 33 US mpg. Always confirm which gallon a source means before converting.
A US legal cup equals 240 mL exactly — this is the definition the FDA uses for nutrition-facts labeling in the United States.
This converter uses the 240 mL legal cup, matching modern US food labels. For quick kitchen math: 1 US cup = 8 US fluid ounces = 16 tablespoons = 48 teaspoons.
Small differences between the 236.588, 240, and 250 mL cups rarely affect cooking, but they matter for precise baking and lab work where SI milliliters are preferred.
Metric volumes convert in clean powers of ten: 1 m³ = 1,000 L = 1,000,000 mL, and 1 mL = 1 cm³ (cubic centimeter) exactly.
To go from cubic meters to liters, multiply by 1,000; from liters to milliliters, multiply by 1,000 again.
The cubic meter is the coherent SI unit of volume defined by the BIPM, and the liter is an accepted non-SI unit equal to one cubic decimeter.
This decimal structure is why the metric system is used in science and medicine — cm³ and mL are interchangeable, which is why syringes, engine displacement, and lab glassware are labeled in either. NIST recommends mL for liquids and cm³ for solids, though the value is identical.
A US fluid ounce equals 29.5735 mL, while a UK (imperial) fluid ounce equals 28.4131 mL — the US ounce is slightly larger.
Despite this, a UK pint (20 imperial fl oz = 568.261 mL) is bigger than a US pint (16 US fl oz = 473.176 mL), because the two systems divide the pint differently. NIST defines the US fluid ounce as 1/128 of a US gallon, and the UK fluid ounce as 1/160 of an imperial gallon.
This mismatch trips up travelers and recipe converters: an "8 oz" US drink is about 237 mL, but 8 imperial ounces is 227 mL, a difference worth noting for precise dosing.
1 cubic foot = 7.48052 US gallons ≈ 28.3168 liters, and 1 cubic inch = 16.3871 mL.
These follow from the exact inch definition: since 1959, 1 inch = 2.54 cm exactly (adopted by NIST and international standards bodies), so 1 in³ = 2.54³ cm³ = 16.387064 cm³, and 1 ft³ = 12³ in³ = 28,316.8 cm³.
To size an aquarium or water tank, multiply cubic feet by 7.48 for US gallons: a 4 ft³ tank holds about 30 US gallons. Cubic feet are common in HVAC, plumbing, and shipping, where volume in cubic feet must be reconciled with liquid capacity in gallons or liters.
One petroleum barrel (bbl) = 42 US gallons = 158.987 liters — the standard used in global crude-oil pricing and trading. This 42-gallon figure was standardized in the 19th-century US oil industry and remains the benchmark today.
Be careful:
This converter uses the petroleum barrel because it dominates commodity markets and energy statistics. When you see a headline oil price "per barrel," it always refers to these 158.987 liters, so multiply a per-barrel price by roughly 0.00629 to estimate cost per liter.
Volume conversion shows up across cooking, science, trade, and home projects.
Because NIST, the BIPM (via SI), and ISO 80000 all publish authoritative conversion factors, using standardized values prevents the costly measurement errors that have historically caused failed batches, dosing mistakes, and even spacecraft losses.
Data sourced from trusted institutions
All formulas verified against official standards.