What is a Unit Converter?
A unit converter translates measurements from one unit to another—like converting miles to kilometers, pounds to kilograms, or Fahrenheit to Celsius. It eliminates the need to remember conversion formulas and handles the math instantly.
With different countries using different measurement systems (metric vs. imperial), a unit converter is essential for international travel, online shopping from foreign sites, or working with instructions in unfamiliar units.
Length/Distance
Miles, kilometers, feet, meters, inches, centimeters
Weight/Mass
Pounds, kilograms, ounces, grams, stones
Temperature
Fahrenheit, Celsius, Kelvin conversions
And More
Area, volume, speed, time, digital storage
Common conversion scenarios:
- International recipes — Converting cups/tablespoons to grams/milliliters
- Travel planning — Understanding distances in km when you think in miles
- Online shopping — Converting clothing sizes between EU/UK/US systems
- Weather apps — Converting Celsius to Fahrenheit or vice versa
- DIY projects — Converting metric hardware specs to imperial or reverse
Exact Conversion Factors and Worked Examples
Many conversion factors people memorize are rounded. The values below are the exact ones defined by the international yard and pound agreement of 1959, so they hold no matter how many decimal places you carry.
Length, weight, and area factors
| From | To | Exact factor |
|---|---|---|
| 1 inch | centimeters | 2.54 (exact) |
| 1 mile | kilometers | 1.609344 (exact) |
| 1 pound | kilograms | 0.45359237 (exact) |
| 1 stone | pounds | 14 |
| 1 acre | square feet | 43,560 |
| 1 acre | hectares | 0.404686 |
Worked example: 5 km to miles
Since 1 mile is 1.609344 km exactly, dividing gets you miles: 5 ÷ 1.609344 = 3.10686 miles, which rounds to about 3.11 miles. Going the other way, a 3.1 mile run is 3.1 × 1.609344 = 4.989 km, just under 5 km.
Why cups do not convert cleanly to grams
A cup measures volume and a gram measures mass, so the conversion depends entirely on what you are measuring. One US cup (236.6 mL) of all-purpose flour weighs roughly 120 g, but the same cup of white sugar weighs about 200 g because sugar is denser. Recipe cups also differ by region: the US cup is 236.6 mL, the metric cup used in Australia is 250 mL, and the older UK cup is 284 mL.
Kilobytes: KB vs KiB
There are two standards. IEC binary prefixes count in powers of two: 1 KiB = 1,024 bytes and 1 GiB = 1,073,741,824 bytes. SI decimal prefixes count in powers of ten: 1 kB = 1,000 bytes. Drive makers advertise in decimal, so a "1 TB" disk holds 1,000,000,000,000 bytes. Windows reports that using binary units, dividing by 1,073,741,824, which shows about 931 GiB. No space is missing; the two systems just count differently.
Temperature landmarks
| Reference | Celsius | Fahrenheit |
|---|---|---|
| Water freezes | 0 | 32 |
| Body temperature | 37 | 98.6 |
| Moderate oven | 180 | 356 |
| Scales cross | -40 | -40 |
Kelvin shares its step size with Celsius but starts at absolute zero, so the offset is exactly 273.15: 0 °C = 273.15 K and 100 °C = 373.15 K. On a practical note, only a few countries still lean on imperial units day to day, chiefly the United States, Liberia, and Myanmar. The UK is mixed: road distances are in miles and pints are pulled in pubs, yet fuel is sold in litres and packaged food is labeled in grams.