Unit Converter
Convert length, weight, and temperature between common units
Converts between units of length, weight, and temperature, updating instantly in either direction — change the "from" value or the "to" value and the other one recalculates.
How it works
Length and weight use a shared base unit (meters and grams respectively) that every other unit converts through, while temperature uses dedicated Celsius/Fahrenheit/Kelvin formulas since those scales don't share a simple multiplier. Editing either field recomputes the other immediately, and results are rounded to 6 significant decimal places to avoid floating-point noise like 2.54000000000001.
Frequently asked questions
Which units are supported?
Length: millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles. Weight: milligrams, grams, kilograms, metric tons, ounces, and pounds. Temperature: Celsius, Fahrenheit, and Kelvin.
Why does it reject negative numbers?
For length and weight, negative values aren't physically meaningful, so they're rejected with an error. Temperature is the exception — negative Celsius or Fahrenheit values are valid and accepted.
Why did it reject my temperature value?
Only values at or above absolute zero (-273.15°C) are accepted — anything colder isn't physically possible, so it's rejected as an error rather than silently converted.
Can I type into either field, or only the "from" side?
Either one — type into "to" and "from" recalculates instead, exactly as if you'd typed into "from" originally. The tool tracks whichever field you last edited as the source.
Is my data sent anywhere?
No — every conversion happens locally in your browser using plain arithmetic. Nothing is uploaded.