Online unit conversion
Convert any unit online in one place
Recipes, packages, workouts, travel, and coursework all need unit conversions. The online length converter covers nine categories in one place, with instant results and a full conversion table on every page, so you never need to remember a formula.
One pattern for every converter
Every converter on the platform works the same way, so the first one you learn teaches you all of them.
Pick the category
Open the converter for the kind of unit you need, from length and weight to temperature, time zones, and currency.
Type the value
Enter any number, decimal, or negative value. There are no fixed presets.
Choose source and target
Select the unit you have and the unit you need, or swap with one click.
Use the full table
The table below shows the same value in every supported unit for comparison.
The conversions people look up most
The most common online conversions are everyday pairs: centimeters to inches, kilograms to pounds, and Celsius to Fahrenheit. Each category page answers them in one step and shows the surrounding units in a table.
For mixed calculations such as body measurements, pair the length converter with the weight converter; for travel planning, combine time zones with currency.
- Length: centimeters, inches, feet, meters, kilometers, miles
- Weight: grams, kilograms, pounds, ounces, stones, tons
- Temperature: Celsius, Fahrenheit, Kelvin
- Data size: bytes, kilobytes, megabytes, gigabytes, terabytes
Where online conversion goes wrong
- Scattered one-off converters that each cover a single pair of units
- Search results that hide the formula and the answer behind ads
- Tools that ask for an account before showing the result
- Outdated conversion factors, especially for data size and currency
Getting conversions right
- Check whether US or UK units apply, especially gallons and tons
- Keep units consistent within one calculation
- Use the full table to sanity-check against a known value
- Remember that volume and weight differ for non-water substances
Frequently asked questions
Which units can I convert online?
Nine categories: length, weight, temperature, area, volume, speed, data size, time zones, and currency. Each page includes a full table of every supported unit.
Are the conversion factors accurate?
Yes. Converters use the standard definitions for each unit, including exact metric prefixes and the common imperial and US customary equivalents.
Do I need an account to convert units?
No. All converters are free and work without an account, and your values are processed locally in the browser.
Can I convert decimal or negative values?
Yes. Every converter accepts decimals, negatives, and large numbers, and results update as you type.
Conversions stay on your device
All unit converters calculate with JavaScript in your browser. The values you type are never uploaded or stored.
Open Length Converter