Unit Converter — Length, Weight, Data and More
Convert 139 units across 12 measurements, including length, weight, volume, temperature, data, pressure, energy and power. Compare results and definitions.
Use the converter
- Choose a measurement type, then the units you are converting from and to.
- Enter the number using a decimal point. You can use thousands separators such as
1,000.5. - Calculate, then open the other-unit results if you need to compare several units at once.
Changing a field clears the old result. The shortcut buttons select a conversion and calculate using the number already entered. Swapping units also keeps that number: swapping after converting 10 cm to inches calculates 10 inches to cm, rather than converting the previous answer back.
What you can convert
| Measurement | Units | Examples available |
|---|---|---|
| Length | 11 | nm, µm, mm, cm, m, km, inches, feet, yards, miles and nautical miles |
| Mass | 8 | µg, mg, g, kg, metric tonnes, ounces, pounds and stones |
| Temperature | 3 | Celsius, Fahrenheit and kelvin |
| Area | 11 | Metric and customary square units, are, hectare, acre and Korean pyeong |
| Volume | 21 | Metric and customary cubic units, litres, US liquid measures and Imperial liquid measures |
| Speed | 7 | m/s, cm/s, km/h, ft/s, ft/min, mph and knots |
| Time | 8 | ns, µs, ms, seconds, minutes, hours, fixed 24-hour days and 7-day weeks |
| Data size | 22 | Bits and bytes, decimal prefixes through peta, and binary prefixes through pebi |
| Data rate | 14 | Decimal bit/s and B/s through tera, plus KiB/s, MiB/s, GiB/s and TiB/s |
| Pressure | 11 | Pa, kPa, MPa, hPa, mbar, bar, atm, psi, Torr, conventional mmHg and kgf/cm² |
| Energy and heat | 13 | J to GJ, Wh to MWh, thermochemical and International Table calories, Btu (IT) and eV |
| Power | 10 | mW to GW, metric PS, mechanical hp, Btu (IT)/h, kcal (th)/h and US refrigeration tons |
A few conversions you can try
- A product measuring 25.4 mm is 1 inch long.
- A 100 Mbps connection converts to 12.5 MB/s. This is a unit conversion, not a prediction of your download speed.
- 1 kWh converts to 3.6 MJ. To work out energy from power, you also need the running time.
Within a category, the tool converts through a common reference unit. Temperatures also need an offset: °F = °C × 9/5 + 32, and K = °C + 273.15. The calculation keeps ratios through to the final display, rather than using an already rounded intermediate result.
Choose the definition that matches the label
MB, MiB and Mbps
Capitalization matters. B means byte; bit means bit. One byte is 8 bits. Decimal prefixes use powers of 1,000, while binary prefixes use powers of 1,024: 1 GB is 1,000,000,000 bytes and 1 GiB is 1,073,741,824 bytes. The tool keeps them separate. See NIST’s binary-prefix definitions and the BIPM SI-prefix table.
US and Imperial liquid measures
The converter gives about 3.78541178 L for 1 US gallon and 4.54609 L for 1 Imperial gallon. Choose the matching system for pints, quarts and fluid ounces too. The cup, tablespoon and teaspoon choices are US customary measures. They do not represent every recipe’s cup size. US dry pints and quarts are not included.
Ounces, feet and area
The mass choices oz and lb are avoirdupois units; they are not troy weights for precious metals. A fluid ounce belongs to volume. Length and area use the international foot rather than the former US survey foot. The tonne choice is a metric tonne. Converting pyeong changes the unit of an area, not whether a property measurement includes shared space.
Temperature readings and temperature changes
Use this tool for a temperature reading. A reading of 10°C is 50°F, but a rise of 10 Celsius degrees is a rise of 18 Fahrenheit degrees. The converter applies the offset and cannot be used directly to convert temperature differences. Values below absolute zero are rejected.
Pressure, heat and horsepower
Pressure conversion does not add or subtract atmospheric pressure: a gauge-pressure input keeps its gauge reference. Negative pressure inputs and conversion between gauge and absolute pressure are not supported. Conventional mmHg uses the NIST table’s rounded factor, 133.3224 Pa; Torr uses 101325/760 Pa. They remain separate choices.
Choose the named calorie definition rather than treating all calories alike. Thermochemical kcal uses 4.184 kJ; International Table kcal uses 4.1868 kJ. Power distinguishes metric horsepower (PS) from mechanical horsepower (hp), and the refrigeration-ton choice uses the US definition. These definitions and qualifications are described in NIST’s conversion-table footnotes.
Input limits and rounding
Enter up to 8 decimal places and a magnitude no greater than 1,000,000,000,000. Use zero or a positive number except for temperature. Scientific notation, fractions such as 1/2 and a comma as the decimal separator are not accepted; enter 0.5 instead. Enter feet and inches as a value in one unit, rather than notation such as 5′ 6″.
Results normally round to 8 decimal places and omit trailing zeroes. A nonzero result smaller than 0.0001 in magnitude uses up to 8 significant digits so that a small conversion does not disappear as zero. A long displayed number does not make a rounded source factor or your original measurement more accurate. Copying a result includes its unit.
You can only convert within one measurement type. Converting mass to volume needs a density; converting power to energy needs a duration. Months and years are excluded because they do not have one fixed length. The day and week choices do not calculate elapsed time between calendar dates or account for daylight saving or leap seconds.
Common questions
Why does the reverse conversion not reproduce my original number?
Swapping the units leaves the input number untouched. To convert the answer back, enter that answer first. Re-entering a rounded result can introduce a rounding difference, and the 8-decimal input limit may prevent you from entering a very small displayed answer exactly.
Does 100 Mbps mean I will download at 12.5 MB/s?
12.5 MB/s is the equivalent unit value. Network overhead, connection quality, the server and other traffic affect the transfer you actually get.
Are my numbers saved?
The converter processes numbers and results in your browser without sending or saving them for this tool. It remembers only the last measurement type and source and destination units in this browser. Returning starts with a default number. Reset clears those saved unit choices. If browser storage is blocked, calculation still works.
Website visits and services are handled separately from these calculations. See the privacy policy. Saved choices are not an account and do not synchronize to another device.
Conversion references
The NIST SI conversion table identifies unit definitions and distinguishes exact factors from rounded ones. The tool uses the selected definitions described above; the table should not be read as saying that every similarly named unit is interchangeable.
Need to compare local dates and working hours? Try the time zone meeting planner. Return to English tools or report a problem.