Convert between metric and US units across six categories — length, weight, temperature, volume, area, and speed — with the result updating live as you type. Pick a category, enter a value, and read the answer; the swap button flips the direction instantly.
What it converts
Length: meters, kilometers, centimeters, millimeters, inches, feet, yards, miles, nautical miles. Weight: kilograms, grams, milligrams, metric tons, ounces, pounds, stone. Temperature: Celsius, Fahrenheit, Kelvin. Volume: liters, milliliters, cubic meters, teaspoons, tablespoons, fluid ounces, cups, pints, quarts, gallons. Area: square meters, kilometers, centimeters, millimeters, inches, feet, yards, acres, square miles. Speed: meters per second, kilometers per hour, miles per hour, feet per second, knots.
Everyday examples
Road trips: 26.2 miles is a marathon — 42.16 km. Cooking: a US recipe’s 2 cups is about 473 ml; a UK pint differs, so check which pint you mean. Body stats: 180 lb is 81.6 kg. Weather: a 75°F day is 23.9°C. Sailing and aviation: 30 knots is about 34.5 mph. Temperature is the one category that isn’t a simple ratio — the converter handles the offsets correctly, so 0°C reads 32°F, not 0.
Conversions use exact international definitions (the inch is exactly 25.4 mm, the pound exactly 0.45359237 kg), computed to six decimal places. Built in-house in plain JavaScript — no widgets, no tracking, nothing you type leaves your device.