Free Unit Converter

How to Use the Unit Converter

Pick a category tab at the top: length, weight, temperature, volume, area, speed, time, or data. Choose your from and to units in the two dropdowns, then type a number in either box. The other box updates instantly, so conversions run both directions. Hit the swap button to flip the units without retyping. The copy button grabs the result for pasting into a recipe, invoice, or homework answer. For the full walkthrough of the math and quick reference charts, see our unit conversion guide.

The Conversions People Look Up Most

These eight answers cover the vast majority of everyday conversion searches. Each one is exact:

When You Need a Unit Converter

Travel. Rental cars abroad quote kilometers and speed limits change at the border. A quick mph to km/h check keeps you legal, and kilometers to miles keeps the road-trip math in your head. Temperature flips too: weather reports in Celsius read very differently from Fahrenheit.

Cooking. Recipes cross borders constantly. American cups and Fahrenheit meet grams and Celsius everywhere else. A wrong conversion ruins a bake; volume to weight needs the ingredient density, but cups to milliliters and Fahrenheit to Celsius are straight conversions this tool handles.

Shipping and selling. International carriers charge by kilogram and centimeter while US listings think in pounds and inches. One decimal-place error on a freight quote costs real money. Double-check dimensions before you print the label.

Homework and DIY. Science classes mix metric and imperial in the same problem set, and hardware store measurements flip between inches, feet, and millimeters. Two-way conversion means you can start from whichever unit the question gave you.

How the Conversions Work

Almost every conversion here is a single multiplication. Each unit is defined by its exact factor relative to a base unit: meters for length, kilograms for weight, liters for volume, square meters for area, meters per second for speed, seconds for time, and bytes for data. Converting means going from your unit to the base unit, then out to the target unit. That two-step path is why the tool can convert between any pair in a category without storing a factor for every combination.

Temperature is the exception: it is not linear because Fahrenheit and Celsius zero points do not line up. Celsius to Fahrenheit is (C × 9/5) + 32, and Fahrenheit to Celsius is (F - 32) × 5/9. Kelvin is just Celsius shifted by 273.15. The tool handles the offsets automatically; details and a full temperature table are in the guide.