Unit Converter (Length, Weight, Temperature)
Convert length (mm, cm, m, km, in, ft, yd, mi), weight (mg, g, kg, t, oz, lb), and temperature (°C, °F, K) into every unit at once from a single input.
Length conversion base values (1 unit = how many meters)
| Unit | Base value |
|---|---|
| Millimeter (mm) | 1 mm = 0.001 m |
| Centimeter (cm) | 1 cm = 0.01 m |
| Meter (m) | 1 m = 1 m |
| Kilometer (km) | 1 km = 1,000 m |
| Inch (in) | 1 in = 0.0254 m |
| Foot (ft) | 1 ft = 0.3048 m |
| Yard (yd) | 1 yd = 0.9144 m |
| Mile (mi) | 1 mi = 1,609.344 m |
Weight conversion base values (1 unit = how many kilograms)
| Unit | Base value |
|---|---|
| Milligram (mg) | 1 mg = 0.000001 kg |
| Gram (g) | 1 g = 0.001 kg |
| Kilogram (kg) | 1 kg = 1 kg |
| Metric ton (t) | 1 t = 1,000 kg |
| Ounce (oz) | 1 oz = 0.028349523125 kg |
| Pound (lb) | 1 lb = 0.45359237 kg |
Temperature conversion formulas
| Celsius to Fahrenheit | °F = °C × 9/5 + 32 |
|---|---|
| Fahrenheit to Celsius | °C = (°F − 32) × 5/9 |
| Celsius to Kelvin | K = °C + 273.15 |
Tips
- Enter one value and pick its unit — every other unit in that category is converted at the same time, so there's no need to look them up one by one.
- Length and weight units convert with a simple ratio, but Celsius, Fahrenheit, and Kelvin each have a different zero point, so temperature can't be converted with a plain ratio.
- Inches, feet, yards, miles, ounces, and pounds have their metric equivalents precisely defined by the 1959 international yard-and-pound agreement, and this tool uses those exact definitions.
- Handy when you need to convert units from foreign recipes (ounces, Fahrenheit) or overseas DIY plans and books (inches, feet).
Frequently Asked Questions
Side Note — The stories behind the meter and the degree Fahrenheit
Today's meter has been defined, since 1983, as the distance light travels in a vacuum in 1/299,792,458 of a second. But the original meter, defined in 1791 by scientists during the French Revolution, was one ten-millionth of the distance from the North Pole to the equator along a meridian. Basing a unit on the Earth itself was a revolutionary attempt to end the chaos of measurements that had varied by region and were often tied to a local ruler's own body (a "foot" literally meaning the length of someone's foot).
Fahrenheit (°F) was devised around 1724 by the German physicist Daniel Gabriel Fahrenheit. He originally set 0 degrees at the freezing point of a brine solution (ice, water, and ammonium chloride) and roughly 96 degrees at human body temperature. More precise later measurements redefined the scale so that water freezes at 32 degrees and boils at 212 degrees, giving us the Fahrenheit scale used today. Because each degree Fahrenheit is a smaller step than a degree Celsius, it can express everyday temperature changes in finer detail, which is one reason it remains in everyday use in the United States.
Many imperial units trace back to everyday body parts and objects from medieval Europe. A "foot" is literally the length of a human foot; a "yard" is thought to derive from the distance from a person's nose to an outstretched hand, or from a standard length used for measuring cloth; and a "mile" comes from the Latin mille passus, meaning a thousand paces marched by Roman soldiers. Where the metric system pursued a universal, reproducible standard, imperial units grew organically out of the everyday human scale — a striking contrast between the two systems.