Unit Conversion Calculators
Convert between metric and imperial units instantly — length, weight, temperature, area, volume, and more. Each calculator shows the conversion formula so you can understand the maths, not just get the answer.
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Length & Distance
Metres to feet, km to miles, centimetres to inches
Weight & Mass
Kg to pounds, grams to ounces, stones to kg
Temperature
Celsius to Fahrenheit and Kelvin conversions
Showing 40 of 40 calculators
Conversion Glossary — Key Terms Explained
- Metric System (SI)
- The International System of Units — used by most of the world. Based on powers of 10 for easy conversion. Key units: metre (length), kilogram (mass), second (time), Kelvin (temperature), litre (volume).
- Imperial System
- The traditional British system still used officially in the US and partially in the UK. Key units: foot/inch/mile (length), pound/ounce/stone (mass), Fahrenheit (temperature), gallon/pint (volume).
- Fahrenheit to Celsius
- °C = (°F − 32) × 5/9. Key reference points: 32°F = 0°C (water freezes); 98.6°F = 37°C (body temp); 212°F = 100°C (water boils).
- Stone (weight)
- A UK unit of weight equal to 14 pounds or 6.35 kilograms. Still widely used in the UK for personal body weight. Not used in the US or most other countries.
- Nautical Mile
- A unit of distance used in maritime and aviation navigation. 1 nautical mile = 1.852 km = 1.151 statute miles. Based on one minute of latitude arc on the Earth's surface.
Frequently Asked Questions
How do I convert Celsius to Fahrenheit?
°F = (°C × 9/5) + 32. Key conversions: 0°C = 32°F; 20°C = 68°F; 37°C = 98.6°F; 100°C = 212°F. Quick mental approximation: double the Celsius temperature and add 30 (gives ±2°F accuracy for temperatures between 0–30°C).
How many kg is a stone?
1 stone = 6.35029 kg. 1 stone = 14 pounds. To convert stones to kg: multiply stones by 6.35. To convert kg to stones: divide kg by 6.35. Example: 11 stone = 11 × 6.35 = 69.85 kg ≈ 70 kg.
How many miles is a kilometre?
1 kilometre = 0.621371 miles. 1 mile = 1.60934 kilometres. Quick approximation: multiply km by 5 and divide by 8. Example: 80 km = 80 × 5/8 = 50 miles (exact = 49.7 miles). Or: 100 km ≈ 62 miles.
How do I convert square metres to square feet?
1 square metre = 10.7639 square feet. To convert m² to ft²: multiply by 10.764. To convert ft² to m²: divide by 10.764 (or multiply by 0.0929). Example: a 20 m² studio flat = 20 × 10.764 = 215 square feet.