Volume Converter
Convert known volume and capacity values among 38 metric, cubic, U.S. liquid, U.S. dry, Imperial and defined petroleum-barrel units. The calculator keeps every defined factor as an exact ratio, distinguishes similarly named systems, and rounds only the final display.
- 38 clearly named units
- Exact rational arithmetic
- U.S. and Imperial units separated
- Decimal or significant-figure rounding
Convert Volume Units
Enter a nonnegative decimal, scientific-notation value, simple fraction or mixed number. Then choose explicit source and target units. This tool converts a known volume; it does not calculate volume from dimensions.
1 US gal converted using the exact 231-cubic-inch definition.
Calculation Steps
- Use 1 US gal = 3.785411784 L exactly.
- Use 1 L = 1 L exactly.
- Multiply 1 US gal by the exact ratio 3.785411784 to obtain 3.785411784 L.
- Round the final value once to 6 decimal places: approximately 3.785412 L.
Every supported unit definition is exact. The main result uses 6 decimal places with nearest rounding, ties to even. Converted digits do not add certainty to the source measurement.
The browser blocked automatic copying. The complete result is selected. Press Ctrl+C on Windows or Command+C on macOS.
How to Use This Volume Converter
Allow about two minutes for one conversion, including a quick check of the unit system and reporting precision.
- Enter one known volume. Use a decimal such as 2.5, scientific notation such as 1e3, a fraction such as 1/2, or a mixed number such as 1 1/2.
- Select the source unit. Choose the full label that matches the original value, including U.S. liquid, U.S. dry or Imperial where required.
- Select the target unit. Choose any supported metric, cubic, customary, dry, Imperial or petroleum-barrel definition.
- Choose display precision. Select decimal places or significant figures, enter the required count, and choose a tie rule.
- Press Convert Volume. Review the rounded answer, exact value, unit ratio, base-unit comparisons and calculation steps.
- Copy, swap or reset. Copy the complete result, swap units without using a rounded display, or restore the default U.S.-gallon example.
Zero is valid. Negative physical volume is rejected. The calculator also rejects unit symbols, commas, malformed fractions and exponents outside its stated range. A nonzero result below the selected decimal resolution is shown in scientific notation instead of being displayed as zero.
Volume Conversion Formula
Every supported unit is stored as an exact number of litres. The calculator first changes the source value to litres, then divides by the target unit's exact litre definition. It performs both operations as one reduced rational calculation.
For example, one U.S. liquid gallon contains exactly 3.785411784 L. Because the target litre contains exactly 1 L, the factor is 3.785411784. Reversing the direction uses its exact reciprocal, 125000000/473176473, whose decimal expansion does not terminate.
A same-unit conversion has a factor of exactly one. Swapping units uses the unrounded target ratio as the new input, so it does not feed the visible rounded answer back into the calculation.
Volume Conversion Examples
Example 1: Convert 1 U.S. liquid gallon to litres
Multiply by the exact U.S.-gallon factor. One U.S. liquid gallon equals exactly 231 cubic inches, which equals exactly 3.785411784 L.
Example 2: Convert 5 litres to U.S. liquid gallons
Divide 5 by 3.785411784. The exact result is 625000000/473176473 US gal, approximately 1.32086026179 US gal.
Example 3: Convert 1 Imperial gallon to litres
The U.K. statutory definition gives one Imperial gallon as exactly 4.54609 L. This is not the U.S. gallon factor.
Example 4: Convert 1 cubic foot to litres
One international foot is exactly 0.3048 m. Cubing this length gives 0.028316846592 m³, or exactly 28.316846592 L.
Example 5: Convert 1 petroleum barrel to U.S. gallons
The supported petroleum barrel is explicitly defined as 42 U.S. liquid gallons. It therefore equals exactly 158.987294928 L. Other commodity barrels can have different definitions.
Metric Volume and Cubic Relationships
The cubic metre, symbol m³, is the SI unit of volume. The litre is a special name for the cubic decimetre. Metric prefixes on litre units scale by ordinary powers of ten. Prefixes on cubic length units are cubed with the unit.
| Relationship | Exact equivalent | Reason |
|---|---|---|
| 1 m³ | 1000 L | A metre contains 10 decimetres; 10³ = 1000 |
| 1 L | 1 dm³ | The litre is the special name for a cubic decimetre |
| 1 mL | 1 cm³ | Both equal 0.001 L |
| 1 µL | 1 mm³ | Both equal 0.000001 L |
| 1 km³ | 1012 L | A kilometre is 1000 m; 1000³ m³ equals 1012 L |
A common mistake is to apply a linear prefix factor only once. One cubic centimetre is not 0.01 m³. It is (0.01 m)³, which equals 0.000001 m³ or 1 mL.
Cubic Inches, Feet, Yards and Acre-Feet
The calculator uses the international inch and foot. One inch equals exactly 0.0254 m, and one foot equals exactly 0.3048 m. Cubing those exact length definitions produces exact volume factors.
| Unit | Exact relationship | Exact litres |
|---|---|---|
| Cubic inch | 1 in³ | 0.016387064 L |
| Cubic foot | 1728 in³ | 28.316846592 L |
| Cubic yard | 27 ft³ | 764.554857984 L |
| Acre-foot | 43,560 ft³, international foot | 1,233,481.83754752 L |
The acre-foot option uses the current international foot. A legacy acre-foot based on the retired U.S. survey foot has a slightly different metric value and is not silently substituted.
U.S. Liquid, U.S. Dry and Imperial Units
Similar names do not guarantee equal sizes. The U.S. liquid gallon is exactly 3.785411784 L, while the Imperial gallon is exactly 4.54609 L. The Imperial gallon is about 20.095% larger. Yet an Imperial fluid ounce is smaller than a U.S. fluid ounce because the Imperial gallon contains 160 fluid ounces and the U.S. gallon contains 128.
| Unit | Exact litres | System note |
|---|---|---|
| U.S. liquid gallon | 3.785411784 L | 231 in³, 4 liquid quarts, 128 US fl oz |
| Imperial gallon | 4.54609 L | 4 Imperial quarts, 160 imp fl oz |
| U.S. liquid quart | 0.946352946 L | Two U.S. liquid pints |
| U.S. dry quart | 1.101220942715 L | One thirty-second of a U.S. dry bushel |
| U.S. fluid ounce | 0.0295735295625 L | One one-hundred-twenty-eighth of a U.S. gallon |
| Imperial fluid ounce | 0.0284130625 L | One one-hundred-sixtieth of an Imperial gallon |
The U.S. cup and spoon options use the exact customary chain: one cup is 8 U.S. fluid ounces, one tablespoon is one-half U.S. fluid ounce, and one teaspoon is one-sixth U.S. fluid ounce. These are not a 240 mL nutrition-label cup, a 250 mL metric cup or an Australian 20 mL tablespoon.
Exact Factors, Rounding and Measurement Precision
The engine stores every entered decimal or fraction and every unit factor as integers over integers. It does not convert through a binary floating-point number. This preserves values such as 1e-1000, exact thirds and long terminating definitions.
The default ties-to-even rule affects an exact halfway case. If the retained digit is even, it stays unchanged; if it is odd, it increases. The optional ties-away rule supports workflows that specify it. Most conversions are not exact ties, so both rules produce the same result.
Exact unit definitions do not make a measurement more accurate. A container marked 1 gal might have manufacturing tolerance. Converting its nominal capacity to 3.785411784 L is mathematically exact, but reporting every digit as measured certainty would overstate the source data.
Common Volume Conversion Mistakes
- Using an unqualified gallon. U.S. liquid and Imperial gallons differ by more than 20%.
- Mixing liquid and dry quarts. One U.S. dry quart is larger than one U.S. liquid quart.
- Treating fluid ounces as mass. Fluid ounce measures volume. Ounce without “fluid” normally measures mass.
- Assuming every cup is the same. U.S. customary, metric and nutrition-label cups use different definitions.
- Forgetting to cube a length factor. Cubic units scale in three dimensions.
- Assuming one litre of every material weighs one kilogram. Mass conversion requires the material's density and applicable conditions.
- Using a generic barrel. This page supports only the petroleum barrel explicitly defined as 42 U.S. liquid gallons.
- Rounding an intermediate factor. Keep the exact ratio and round the final result once.
Related Calculators
Frequently Asked Questions
How do I convert one volume unit to another?
Multiply the entered value by the exact litres per source unit, then divide by the exact litres per target unit. This calculator combines those operations into one reduced ratio and rounds only the final display.
How many litres are in a U.S. gallon?
One U.S. liquid gallon equals exactly 3.785411784 L. It also equals exactly 231 cubic inches, 4 U.S. liquid quarts or 128 U.S. fluid ounces.
Are U.S. and Imperial gallons the same?
No. One U.S. liquid gallon equals exactly 3.785411784 L, while one Imperial gallon equals exactly 4.54609 L. Select the system stated by the source measurement.
Is 1 millilitre equal to 1 cubic centimetre?
Yes. One millilitre equals exactly one cubic centimetre. One litre equals exactly one cubic decimetre, and one microlitre equals exactly one cubic millimetre.
Are U.S. dry and liquid quarts equal?
No. One U.S. dry quart equals exactly 1.101220942715 L, while one U.S. liquid quart equals exactly 0.946352946 L. The full unit label matters.
Why do cubic conversions use the third power?
Volume has three dimensions. A linear factor applies to length, width and height, so it is cubed. Since 1 yd equals 3 ft, 1 yd³ equals 3³, or 27 ft³.
Can I convert volume directly to mass?
No. A volume-to-mass conversion requires the substance's density and sometimes temperature or pressure. This page converts volume units without assuming the substance is water.
Which cup, tablespoon and teaspoon does this converter use?
It uses U.S. customary definitions: 1 cup = 8 U.S. fluid ounces, 1 tablespoon = 1/2 U.S. fluid ounce, and 1 teaspoon = 1/6 U.S. fluid ounce. Other culinary and lab conventions differ.
How many gallons are in a petroleum barrel?
The petroleum barrel option equals exactly 42 U.S. liquid gallons, or exactly 158.987294928 L. A barrel for another commodity may use a different definition.
Can I enter fractions or scientific notation?
Yes. Enter a decimal, scientific notation, simple fraction or mixed number without a unit symbol or comma. Zero is accepted, negative physical volume is rejected, and the supported exponent range is -1000 to 1000.
Method and Official Sources
SI volume and litre relationships follow the BIPM SI Brochure and NIST SI Units: Volume. Exact cubic, U.S. liquid and U.S. dry relationships follow NIST Handbook 44, 2026, Appendix C. Additional conversion and rounding guidance follows NIST SP 811, Appendix B. Imperial definitions follow the U.K. Weights and Measures Act 1985, Schedule 1.
Measurement note: This tool converts a stated volume or capacity. It does not calculate geometry, density, mass, flow, medication dose, container tolerance, gas volume at reference conditions or uncertainty. Confirm the original unit system before relying on a result.