Convert Between Metric and Imperial Units
This unit converter handles the conversions people need most across five categories: length, weight, temperature, volume and area. Choose a category, enter a value and pick the units to convert from and to. The result appears instantly, along with the formula used, so you can see exactly how the answer was reached.
Common Conversions
- Length: 1 inch = 2.54 cm, 1 foot = 0.3048 m, 1 mile = 1.609 km.
- Weight: 1 pound = 0.4536 kg, 1 ounce = 28.35 g, 1 kg = 2.2046 lb.
- Volume: 1 U.S. gallon = 3.785 liters, 1 cup = 236.6 ml.
- Area: 1 acre = 43,560 sq ft = 4,047 m².
- Temperature: °F = °C × 9/5 + 32, and °C = (°F − 32) × 5/9.
How Conversion Works
Most conversions multiply by a fixed factor. Each unit is converted to a base unit (such as meters or kilograms) and then to the target unit. Temperature is different because the scales have different zero points, so the converter uses a formula rather than a single factor.
Example: 25 °C × 9/5 + 32 = 77 °F, and 10 miles × 1.609 = 16.09 km.
Frequently Asked Questions
Why can't temperature be converted with a single multiplier?
Celsius and Fahrenheit start at different zero points: water freezes at 0 °C but at 32 °F. The conversion needs both a multiplication and an addition or subtraction, unlike length or weight.
Is a U.S. gallon the same as a UK gallon?
No. A U.S. gallon is about 3.785 liters, while an imperial (UK) gallon is about 4.546 liters, roughly 20% larger. Check which gallon your recipe or vehicle uses.
What is the quickest way to estimate kilometers from miles?
Multiply miles by 1.6. For a rough reverse estimate, multiply kilometers by 0.6. For example, 5 km ≈ 3.1 miles.