Unit Converter
Free unit converter online. Convert length, weight, temperature, area, volume, speed, and time instantly. No sign-up needed.
Unit Converter
Comprehensive Guide & Practice
Master the mathematical principles, formulas, and step-by-step methods with worked examples and FAQs.
1. How to Convert Between Units
Unit conversion is the process of expressing the same physical quantity in a different unit of measurement. The key principle: multiply by a conversion factor — a fraction equal to 1, where the numerator and denominator express the same quantity in different units.
For example: 1 kilometre = 1000 metres. To convert 5 km to metres: 5 × 1000 = 5,000 m.
2. Length Conversions
The metric system is built on powers of 10. Key conversions: 1 km = 1,000 m | 1 m = 100 cm | 1 cm = 10 mm. Imperial: 1 mile = 1,760 yards = 5,280 feet. 1 foot = 12 inches. Metric to Imperial: 1 km ≈ 0.621 miles | 1 m ≈ 3.281 feet | 1 cm ≈ 0.394 inches.
3. Temperature Conversions
Three common scales: Celsius (°C), Fahrenheit (°F), and Kelvin (K). Formulas: °F = (°C × 9/5) + 32 and K = °C + 273.15. Key points: Water freezes at 0°C = 32°F. Water boils at 100°C = 212°F. Absolute zero = 0K = −273.15°C.
4. Weight Conversions
Metric: 1 kg = 1,000 g. Imperial: 1 lb = 16 oz | 1 stone = 14 lb. Metric to Imperial: 1 kg ≈ 2.205 lb | 1 g ≈ 0.035 oz.
See also: Geometry Calculator | Speed Calculator | Scientific Notation