Convert a measurement between compatible units of length, mass, temperature, area, volume, speed, time, digital storage, pressure or energy. Choose the category first, then check the full unit names: a US gallon and an imperial gallon are different quantities.
Unit Converter
Convert between units of length, weight, temperature, area, volume, speed, time, digital storage, pressure and energy — instantly, with a full conversion table for every result.
Full conversion table
Note: Conversions use standard international factors. Choose US or UK (imperial) gallons carefully. The smaller customary volume units listed here use US measures. Rounding is applied for display.
How to use this unit converter
- Choose the measurement category, such as Length or Volume.
- Enter the numeric value. Select its original unit under From and the required unit under To.
- Read the result with its unit. The comparison table shows the same quantity in the other units available in that category.
- Use the swap button to reverse the selected units. Check the input value again before treating the reversed calculation as a new measurement.
Keep the original measurement and unit with your answer. A result of “12” alone does not say whether you mean inches, centimetres, litres or something else.
Worked conversions you can check
| Convert | Calculation | Result |
|---|---|---|
| 12 inches to centimetres | 12 × 2.54 | 30.48 cm |
| 5 kilometres to metres | 5 × 1,000 | 5,000 m |
| 10 square feet to square metres | 10 × 0.3048² | 0.9290304 m² |
| 2 cubic metres to litres | 2 × 1,000 | 2,000 L |
| 20 degrees Celsius to Fahrenheit | (20 × 9 ÷ 5) + 32 | 68 °F |
These examples show the mathematical value before any rounding in the tool’s display. The international foot is 0.3048 metres and the inch is 2.54 centimetres. Conversion factors are documented in NIST’s conversion tables.
Three mistakes that change the answer
Using a length factor for area or volume
Area uses a squared factor; volume uses a cubed factor. Because 1 metre is 100 centimetres, 1 m² is 10,000 cm² and 1 m³ is 1,000,000 cm³. Multiplying a square-metre value by only 100 gives the wrong area.
Choosing the wrong gallon or ounce
US customary and British imperial units share some names but differ for liquid volume. One US liquid gallon is 3.785411784 litres; one imperial gallon is 4.54609 litres. Read the unit label carefully: the gallon choices include US and UK, while the smaller customary volume choices on this tool use US measures. An ounce of mass and a fluid ounce of volume also belong to different categories.
Treating a temperature as a simple ratio
Celsius and Fahrenheit have different zero points. For a temperature reading, use °F = °C × 9/5 + 32. For a change in temperature, omit the offset: a rise of 10 °C is a rise of 18 °F. This tool converts temperature readings.
Entering feet and inches as one value
The input accepts one numeric value, so convert a mixed measurement before entering it. For 5 feet 9 inches, calculate 5 × 12 + 9 = 69 inches, then select inches as the starting unit. The equivalent decimal-foot value is 5 + 9/12 = 5.75 feet. Entering 5.9 feet means 5 feet and 10.8 inches, which is a different height.
Digital storage: MB and MiB are different
One megabyte (MB) is 1,000,000 bytes. One mebibyte (MiB) is 1,048,576 bytes. A byte contains 8 bits, so lowercase b and uppercase B matter. This tool lists decimal kB, MB, GB and TB separately from binary KiB, MiB, GiB and TiB. Choose the label used by your source instead of assuming every storage unit uses 1,024. See NIST’s binary-prefix reference for the decimal and binary definitions.
What this tool can and cannot convert
The two units must describe the same kind of quantity. Kilograms can become pounds, but kilograms cannot become litres without a material’s density. Cups cannot become grams without an ingredient-specific relationship. Clothing sizes, exchange rates and school credits are outside this tool’s measurement categories.
For ingredient quantities, use the Recipe Scaler. To calculate a shape before converting its units, use the Area Calculator or Volume Calculator. For calendar dates rather than fixed time units, use the Date Difference Calculator.
How many decimal places should I keep?
A conversion can display more digits than your measurement justifies. Converting a roughly measured 2-metre shelf into inches does not make that measurement exact. Keep extra digits while working, then round the final result to suit the precision of the original measurement. The tool’s displayed rounding is separate from measurement uncertainty.
Fixed time units versus calendar dates
A minute is 60 seconds and an hour is 60 minutes. The converter uses a fixed 365.25-day year for its year unit. A calendar year can contain 365 or 366 days, and months have different lengths. A time-unit conversion cannot answer how many days remain until a birthday or deadline; enter the actual dates in the Date Difference Calculator for that task.