Free Unit Converter
Convert length, weight, temperature, volume, speed and area instantly. Metric to imperial and back.
Common Conversions
How Unit Conversion Works
Unit conversion multiplies or divides a value by a known conversion factor. For example, 1 inch = 2.54 centimetres, so 10 inches = 10 x 2.54 = 25.4 cm. Temperature conversion is different — it uses a formula rather than a simple multiplier: Fahrenheit = (Celsius x 9/5) + 32. This converter handles six categories: length, weight, temperature, volume, speed, and area, covering all the conversions you need for travel, cooking, science, and everyday life.
Length Conversion Reference
Weight Conversion Reference
Temperature Formulas
- Celsius to Fahrenheit: (C x 9/5) + 32. Example: 100°C = 212°F
- Fahrenheit to Celsius: (F - 32) x 5/9. Example: 72°F = 22.2°C
- Celsius to Kelvin: C + 273.15. Example: 0°C = 273.15 K
Key reference points: water freezes at 0°C / 32°F, boils at 100°C / 212°F. Room temperature is about 20-22°C / 68-72°F. Body temperature is 37°C / 98.6°F.
Metric vs Imperial
The metric system (officially the International System of Units, SI) is used by virtually every country. It uses base-10 prefixes: kilo (1,000), centi (1/100), milli (1/1,000). The imperial system uses feet, pounds, gallons, and Fahrenheit. The United States is the only major country that hasn't officially adopted metric, though the UK uses a mix — kilometres on road signs, miles in daily speech, kilograms in shops, and stone for body weight.
Volume: UK vs US Gallons
The UK gallon (4.546 litres) is about 20% larger than the US gallon (3.785 litres). This causes confusion in fuel economy comparisons. A car getting 40 miles per US gallon gets about 48 miles per UK gallon. When converting recipes between American and British cookbooks, cup measurements also differ: a US cup is 236 ml while a metric cup (used in UK/Australia) is 250 ml.
Conversion Tips for Travel
- Quick km to miles: Multiply by 0.6 for a rough estimate (100 km ≈ 60 miles)
- Quick kg to lbs: Double it and add 10% (70 kg ≈ 140 + 14 = 154 lbs)
- Quick C to F: Double and add 30 for a rough estimate (20°C ≈ 70°F)
- Quick litres to gallons: Divide by 4 for rough US gallons (8 litres ≈ 2 gallons)
Related Tools
Frequently Asked Questions
Multiply by 0.6214. Quick trick: multiply by 0.6 for an estimate. 10 km ≈ 6.2 miles.
(°C x 9/5) + 32. Example: 20°C = 68°F. Quick trick: double and add 30.
1 kg = 2.2046 lbs. Quick trick: double the kg and add 10%.
UK gallon = 4.546 litres. US gallon = 3.785 litres. UK is about 20% larger.
Metric uses base-10 (metres, kg, litres). Imperial uses feet, pounds, gallons. Most of the world uses metric.
Results are accurate to 4 decimal places using standard conversion factors.
