Convert between metric and imperial units for length, weight, temperature, volume, speed, and area. Works both directions — type in either field.
Convert between metric (mm, cm, m, km) and imperial (in, ft, yd, mi)
Convert between kg, g, lb, oz, stone, and more
Convert between Celsius, Fahrenheit, and Kelvin
Convert between liters, ml, gallons, cups, fl oz, and more
Convert between km/h, m/s, mph, knots, and more
Convert between m², km², hectares, sq ft, sq mi, acres, and more
Quick Reference — Most Common Conversions
| Metric | Imperial |
|---|---|
| 1 cm | 0.394 in |
| 1 m | 3.281 ft / 1.094 yd |
| 1 km | 0.621 mi |
| 1 kg | 2.205 lb |
| 1 kg | 0.157 st |
| 1 g | 0.035 oz |
| 1 metric ton | 2,204.6 lb |
| Metric | Imperial / US |
|---|---|
| 1 liter | 0.264 gal / 33.8 fl oz |
| 1 liter | 2.113 pt / 4.227 cups |
| 1 ml | 0.202 tsp / 0.068 tbsp |
| 1 km/h | 0.621 mph |
| 1 m/s | 3.281 fps |
| 1 hectare | 2.471 acres |
| 1 m² | 10.764 ft² |
Metric system (SI): Used by ~95% of the world. Based on powers of 10 — every unit is 10× the next smaller unit. Length: millimeter → centimeter → meter → kilometer. Weight: milligram → gram → kilogram → metric ton.
Imperial system: Used primarily in the United States, and partially in the UK and Canada. Based on historical conventions without a consistent multiplier — 12 inches in a foot, 3 feet in a yard, 1,760 yards in a mile, 16 ounces in a pound, 14 pounds in a stone.
Why both matter: Science and medicine use metric globally. US recipes, road signs, and product specs use imperial. Most international travel, shipping, and trade requires both.
Temperature note: Fahrenheit and Celsius cross at −40° (−40°C = −40°F). The formula: °F = (°C × 9/5) + 32. Water freezes at 0°C / 32°F and boils at 100°C / 212°F at sea level.