Unit Converter
Fast, precise conversions for length, weight, temperature, and more.
Length Conversion
About this converter
Enter a value to instantly convert between common length units. Results are computed with high-precision constants.
How ConvertMaster works
Every conversion on this site is computed from internationally recognized base units. Length conversions reduce each unit to meters; weight to kilograms; volume to liters; and area to square meters. Temperature is the only category that can't be expressed as a single multiplier — Celsius, Fahrenheit, and Kelvin each require an offset, so we apply the standard formulas°F = °C × 9/5 + 32 andK = °C + 273.15 directly.
Constants come from the International System of Units (SI) and the National Institute of Standards and Technology (NIST). For example, one inch is defined as exactly 0.0254 meters, one pound as exactly 0.45359237 kilograms, and one US gallon as exactly 3.785411784 liters. Because these definitions are exact, your answer is limited only by how many digits you choose to display.
Quick reference: common conversions
These are the conversions our visitors look up most often. Use them as a sanity check, or memorize the rounded values for quick mental math.
| From | To | Exact | Rounded |
|---|---|---|---|
| 1 meter | feet | 3.28083989501… | 3.28 ft |
| 1 mile | kilometers | 1.609344 | 1.61 km |
| 1 inch | centimeters | 2.54 | 2.54 cm |
| 1 kilogram | pounds | 2.20462262185… | 2.20 lb |
| 1 ounce | grams | 28.349523125 | 28.35 g |
| 100 °C | °F | 212 | 212 °F |
| 0 °F | °C | −17.7777… | −17.78 °C |
| 1 US gallon | liters | 3.785411784 | 3.79 L |
| 1 acre | square meters | 4046.8564224 | 4046.86 m² |
| 1 hectare | acres | 2.47105381… | 2.47 ac |
Frequently asked questions
How accurate are the results?
Calculations use double-precision floating-point arithmetic with exact SI conversion factors. Results are displayed to up to six significant decimals; for engineering work that requires more precision, copy the value into a spreadsheet and apply the underlying factor directly.
Why are US and Imperial gallons different?
The US gallon (3.785411784 L) is based on the historical Queen Anne wine gallon, while the Imperial gallon (4.54609 L) was defined in 1824 by the British Weights and Measures Act. The two coexist today, which is why fuel economy numbers don't translate cleanly between the US and the UK.
Do you store the values I enter?
No. All conversions happen entirely in your browser. Nothing you type is sent to a server or saved.
Is ConvertMaster free to use?
Yes. The converter is free for personal, educational, and professional use. We support the site through unobtrusive advertising — see the privacy page for details.