Unit Converter
Convert length units instantly with this free unit converter. Switch between millimeters, centimeters, meters, kilometers, inches, feet, yards and miles.
About this tool
People around the world measure length in different units. The metric system uses millimeters, centimeters, meters and kilometers, while the United States and a few other countries use inches, feet, yards and miles. When you read a product specification, a recipe or a travel distance, you often need to switch between these systems quickly.
Our free unit converter does the conversion for you instantly. Type a value, pick the unit you have and the unit you want, and the tool calculates the exact result. It is perfect for students, engineers, travelers and anyone who works with measurements from different countries.
How to use
Using the unit converter takes three quick steps. First, enter the number you want to convert in the value field. Next, choose the unit you are converting from in the first dropdown, for example inches. Finally, choose the target unit in the second dropdown, such as centimeters, and press the Convert button.
The result appears immediately below the button. You can change any of the inputs and convert again as many times as you like. The tool runs entirely in your browser, so there is no waiting and your numbers are never sent anywhere.
The math behind it
Every conversion goes through meters, the base unit of length. Each unit has a fixed international factor: one inch is exactly 0.0254 meters, one foot is 0.3048 meters, one mile is 1609.344 meters, and so on. To convert, the tool first multiplies your value by the from-unit factor to get meters, then divides by the to-unit factor.
Because these factors are exact definitions, the results are precise. Rounding is only applied when the result is displayed, so you always see a clean, readable number.