Unit Converter

Length, weight, temperature and more - instant results, no sign-up.

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A unit converter takes a value in one unit - centimeters, kilograms, Celsius, square feet - and gives you the equivalent in another. The tool above handles length, weight, temperature, area, and volume in a single place. The conversions use exact ratios (1 inch is exactly 2.54 cm by international agreement; pounds and kilograms relate by exactly 2.20462262), so the answer matches what an engineering reference would give you.

How conversions work

Most units are connected by a fixed multiplier. To convert a value, multiply by the right ratio:

  • Length: 1 inch = 2.54 cm exactly. 1 foot = 12 in = 30.48 cm. 1 mile = 1.609344 km. To convert km to miles, multiply by 0.621371.
  • Weight: 1 kg = 2.20462 lbs. 1 lb = 0.45359 kg. 1 ounce ≈ 28.35 g. The pound is defined in terms of the kilogram, so the conversion is exact to many decimal places.
  • Area: Squared units multiply differently. 1 m² = 10.7639 ft² (it's 3.28084², not 3.28084). Same for any "squared" unit - multiply the linear conversion by itself.
  • Volume: Cubed similarly. 1 m³ = 35.3147 ft³ (3.28084³). 1 US gallon = 3.78541 liters; 1 UK gallon = 4.54609 liters - note these are different.

Temperature is the exception. Because Celsius and Fahrenheit don't share a zero point, you can't just multiply. The full formula is °F = (°C × 9/5) + 32, and °C = (°F − 32) × 5/9. Kelvin is offset from Celsius by exactly 273.15 (0°C = 273.15 K, 100°C = 373.15 K).

Common conversions, at a glance
Length

1 inch = 2.54 cm · 1 foot = 30.48 cm · 1 yard = 0.9144 m · 1 mile = 1.609 km · 1 nautical mile = 1.852 km

Weight / mass

1 kg = 2.205 lbs · 1 lb = 453.59 g · 1 oz = 28.35 g · 1 stone = 6.35 kg · 1 metric ton = 1,000 kg = 2,204.6 lbs

Temperature reference points

Water freezes: 0°C = 32°F = 273.15 K · Body temp: 37°C = 98.6°F · Water boils (sea level): 100°C = 212°F · Comfortable room: 20°C = 68°F

Volume

1 liter = 33.81 fl oz (US) · 1 US gallon = 3.785 L · 1 UK gallon = 4.546 L · 1 cup = 240 mL · 1 tablespoon = 14.79 mL

Frequently asked questions
How many centimeters are in an inch?
Exactly 2.54 cm by international definition. To convert inches to centimeters, multiply by 2.54. To go the other way, divide by 2.54 (or multiply by 0.3937).
How do I convert kilograms to pounds?
Multiply kilograms by 2.20462 to get pounds. So 70 kg × 2.20462 ≈ 154.32 lbs. To convert pounds to kilograms, divide by 2.20462 (or multiply by 0.45359).
What is the formula for Celsius to Fahrenheit?
°F = (°C × 9/5) + 32. For example, 20°C = (20 × 1.8) + 32 = 68°F. The reverse is °C = (°F − 32) × 5/9. Unlike length or weight, temperature isn't a simple multiplication because the two scales don't share a zero point.
How many feet are in a meter?
1 meter = 3.28084 feet. To convert meters to feet, multiply by 3.28084. To go the other way, divide by 3.28084 (or multiply by 0.3048). For squared units (square meters to square feet), multiply by 10.7639 - that's 3.28084 squared.
Why are US and UK gallons different?
They're historically distinct units. A US gallon is 3.785 liters; a UK (imperial) gallon is 4.546 liters - about 20% larger. This matters when reading recipes, fuel-economy figures, or international product specs. The tool above uses US gallons by default; the conversion is shown explicitly.
What's the difference between mass and weight?
Mass is how much matter something contains (kilograms, pounds-mass). Weight is the gravitational force on that mass (newtons, pounds-force). On Earth they're proportional and people use the words interchangeably; in physics or engineering they're distinct. This calculator uses everyday convention.
How precise are the conversions?
All ratios used are accurate to the level reference tables provide - typically 5+ significant figures. For everyday use the answers are exact for any practical purpose. For scientific or legal precision, double-check the specific definition that applies in your context.
Can I convert between unrelated units (kg to inches)?
No. You can only convert between units of the same physical quantity - length to length, mass to mass, volume to volume. Some specialized fields use density to convert between mass and volume (1 liter of water ≈ 1 kg) but that's a different operation.