Developer Tools
Unit Converter Online
Convert everyday measurements with explicit unit definitions, instant results and formulas you can check.
Conversions stay in this browser tab. No values are uploaded, logged or saved.
Use a decimal point or scientific notation (for example, 2.5e3). Signed values are allowed for mathematical conversions; temperatures must be at or above absolute zero.
Result = input × 0.621371192237
1 km ≈ 0.621371192237 mi
International inch, foot, yard and mile; nautical mile = 1,852 meters.
Results and factors are displayed to at most 12 significant digits, with scientific notation for extreme values. Calculations use floating-point numbers; displayed and copied results may be rounded.
What is a unit converter?
A unit converter expresses the same quantity in a different measurement unit. Use this free tool to compare distances, weights, temperatures, areas, volumes, speeds, durations, storage sizes, pressures, energy and power.
How to use the converter
- Choose a measurement category and the source and target units.
- Enter a number. The result updates as you type; no submit button is needed.
- Check the unit definition and formula, then copy the displayed result if needed.
- Swap exchanges the units while keeping your input number. Clear removes the number.
Metric, imperial and US customary units
Metric conversions use powers of ten. International inches, feet and miles have defined relationships to meters. Volume needs more care: this converter uses US liquid measures, not Imperial gallons or dry measures. Mass uses avoirdupois ounces and pounds, not troy weights.
Decimal vs binary data storage
Decimal units use 1,000 at each step: 1 GB = 1,000 MB. Binary units use 1,024: 1 GiB = 1,024 MiB. A GB and a GiB are different quantities. These are bytes, not bits or transfer rates.
Celsius, Fahrenheit and Kelvin
Temperature scales need offsets as well as factors. Use °F = °C × 9/5 + 32 or K = °C + 273.15. For example, 0 °C is 32 °F and 273.15 K. These formulas convert absolute temperatures, not temperature changes.
Common conversion examples
- 1 inch = 2.54 centimeters.
- 1 foot = 0.3048 meters.
- 1 mile = 1.609344 kilometers.
- 1 pound = 0.45359237 kilograms.
- 1 US liquid gallon = 3.785411784 liters.
- 1 kilowatt-hour = 3,600,000 joules.
Definitions and limits
Factors use defined constants where available, but browser arithmetic has finite precision. Very large or small unrepresentable results produce a message instead of Infinity or a misleading zero. Negative values support signed mathematical quantities; they do not imply that every physical quantity can be negative. Calendar months and years are excluded.
Energy uses thermochemical calories and International Table BTU. Horsepower is mechanical horsepower. Conventional mmHg and torr are separate units. Pressure conversion does not change gauge pressure into absolute pressure.
Reference: NIST conversion factors. This reference opens only when selected; calculations do not contact it.
Supported units by category
Length
Millimeter (mm), Centimeter (cm), Meter (m), Kilometer (km), Inch (in), Foot (ft), Yard (yd), Mile (mi), Nautical mile (nmi).
Weight / Mass
Milligram (mg), Gram (g), Kilogram (kg), Metric ton (t), Ounce (avoirdupois) (oz), Pound (avoirdupois) (lb), Stone (st).
Temperature
Celsius (°C), Fahrenheit (°F), Kelvin (K).
Area
Square millimeter (mm²), Square centimeter (cm²), Square meter (m²), Square kilometer (km²), Square inch (in²), Square foot (ft²), Square yard (yd²), Acre (ac), Hectare (ha), Square mile (mi²).
Volume
Milliliter (mL), Liter (L), Cubic meter (m³), US teaspoon (US tsp), US tablespoon (US tbsp), US fluid ounce (US fl oz), US customary cup (US cup), US liquid pint (US pt), US liquid quart (US qt), US liquid gallon (US gal).
Speed
Meters per second (m/s), Kilometers per hour (km/h), Miles per hour (mph), Knot (kn), Feet per second (ft/s).
Time
Millisecond (ms), Second (s), Minute (min), Hour (h), Day (24 hours) (d), Week (7 days) (wk).
Data Storage
Byte (B), Kilobyte (decimal) (KB), Megabyte (decimal) (MB), Gigabyte (decimal) (GB), Terabyte (decimal) (TB), Kibibyte (binary) (KiB), Mebibyte (binary) (MiB), Gibibyte (binary) (GiB), Tebibyte (binary) (TiB).
Pressure
Pascal (Pa), Kilopascal (kPa), Megapascal (MPa), Bar (bar), Pounds-force per square inch (psi), Standard atmosphere (atm), Torr (Torr), Millimeter of mercury (conventional) (mmHg).
Energy
Joule (J), Kilojoule (kJ), Calorie (thermochemical) (cal), Kilocalorie (thermochemical) (kcal), Watt-hour (Wh), Kilowatt-hour (kWh), BTU (International Table) (BTU IT).
Power
Watt (W), Kilowatt (kW), Megawatt (MW), Horsepower (mechanical) (hp).
Frequently asked questions
How many centimeters are in an inch?
One international inch is exactly 2.54 centimeters. Multiply inches by 2.54 to get centimeters.
How do I convert kg to pounds?
Divide kilograms by 0.45359237. One kilogram is approximately 2.20462262185 pounds.
How do I convert Celsius to Fahrenheit?
Multiply Celsius by 9/5, then add 32. For example, 100 °C is 212 °F.
Is 1 GB the same as 1 GiB?
No. One GB is 1,000,000,000 bytes; one GiB is 1,073,741,824 bytes.
Are conversions processed locally?
Yes. All calculations happen in your browser. Values are not sent to an API or saved in browser storage.