About the unit converter
Recipes from another country, a furniture listing in inches, a weather forecast in Fahrenheit, a speed limit in miles per hour: everyday life constantly mixes the metric and imperial systems. This converter covers the six categories people need most often and shows the answer as soon as you type.
Every factor is the exact legal definition, not a rounded approximation. Since 1959 the international inch has been defined as exactly 2.54 cm and the pound as exactly 0.45359237 kg, and US customary volumes are defined from the cubic inch. Results are shown to ten significant digits, and you can open the full table to see your value in every unit at once.
How to use it
- Choose a category: length, weight, temperature, area, volume or speed.
- Type the value you want to convert.
- Choose the from and to units. Use the swap button to reverse the conversion.
- Copy the result, or open “Convert to every unit” to see all equivalents.
Common conversion factors
| From | To | Multiply by |
|---|---|---|
| Inches | Centimeters | 2.54 |
| Feet | Meters | 0.3048 |
| Miles | Kilometers | 1.609344 |
| Pounds | Kilograms | 0.45359237 |
| Ounces | Grams | 28.349523125 |
| US gallons | Liters | 3.785411784 |
| Acres | Square meters | 4,046.8564224 |
| Miles per hour | Kilometers per hour | 1.609344 |
Temperature is different because the scales have different zero points: °F = °C × 9 ÷ 5 + 32, and K = °C + 273.15.
Examples
- A 6 ft person is 6 × 0.3048 = 1.8288 m (about 183 cm) tall.
- A 70 kg weight is 70 ÷ 0.45359237 ≈ 154.32 lb.
- A 180 °C oven is 180 × 9 ÷ 5 + 32 = 356 °F.
- Driving at 100 km/h is about 62.14 mph.
More worked examples
Height: 5 ft 10 in is 70 inches × 2.54 = 177.8 cm.
Weather: 30 °C is 30 × 9 ÷ 5 + 32 = 86 °F.
Running: a marathon is 42.195 km, or about 26.22 miles.
Common mistakes to avoid
- Mixing US and imperial gallons. A US gallon is 3.785 liters; an imperial gallon is 4.546 liters.
- Converting temperatures with a single factor. Celsius and Fahrenheit have different zero points, so you must add or subtract 32.
- Rounding too early. Round only the final answer. To check body weight in kg or lbs against a healthy range, use the BMI calculator.
Sources and methodology
The calculations on this page follow these published standards and references. The code is covered by automated tests against known values.