Unit Converter
Convert between metric and US units — length, weight, temperature, volume, area, and speed. Results update as you type.
Popular conversions
Each has its own page with the formula and a reference table:
- Centimeters to inches · Feet to centimeters · Kilometers to miles
- Kilograms to pounds · Grams to ounces · Stone to kilograms
- Celsius to Fahrenheit · Fahrenheit to Celsius
- Liters to gallons · Milliliters to fluid ounces · Cups to milliliters
- Square meters to square feet · Acres to square feet
- km/h to mph · mph to km/h
Browse all 50+ conversion pages.
Metric vs. US customary: a 60-second primer
Nearly every country uses the metric system (meters, kilograms, liters, Celsius). The United States is the major exception, using customary units (feet, pounds, gallons, Fahrenheit) for daily life. The UK sits in between — metric officially, but miles on road signs and stone for body weight.
Handy anchors: a meter is a bit over 3 feet · a kilogram is about 2.2 pounds · a liter is about a quarter of a US gallon · 20°C is a pleasant 68°F room.
Frequently asked questions
Are these US or UK (imperial) units?
US customary. Gallons and fluid ounces differ between the two systems — a UK gallon is about 20% larger. Length and weight units (inches, feet, pounds) are the same in both.
How precise are the conversions?
Conversion factors are exact by international definition (1 inch = exactly 2.54 cm; 1 lb = exactly 0.45359237 kg). Displayed results are rounded to six significant digits.
Does this work offline?
Once loaded, yes — all conversion happens in your browser, nothing is sent to a server.