Unit Converter
Instantly convert between temperature, length, weight, volume, speed, area, and data storage units.
About This Converter
All conversions use exact SI conversion factors. Temperature conversions use the precise formulas (°C = (°F − 32) × 5/9). For very large or very small values, the result is shown in scientific notation automatically.
Everything About the Unit Converter
How unit conversion works, the key formulas, and quick mental math shortcuts for everyday use.
How It Works
- Select a unit category (temperature, length, weight, volume, speed, area)
- Choose your source unit and target unit
- Enter the value to convert
- Instant result using exact SI conversion factors
- Reverse conversion with one click
The Formula
°F = °C × 9/5 + 32 °C = (°F−32) × 5/9
1 mile = 1.60934 km 1 kg = 2.20462 lbs
1 ft = 0.3048 m 1 oz = 28.3495 g
For most categories: Target = Source × Conversion Factor (exact constant). Temperature uses an additive offset formula.
Pro Tips
- Quick °C to °F: double the Celsius and add 30 (rough estimate, exact: ×1.8 + 32)
- Speed: 60 mph ≈ 100 kph (actual 96.6 kph — close enough for road trips)
- 1 liter ≈ 1.06 US quarts; 1 gallon = 3.785 L — useful at the gas pump abroad
- Body temp: 37°C = 98.6°F; oven baking: 180°C = 356°F
Frequently Asked Questions
How do I convert Celsius to Fahrenheit and back? +
°F to °C: subtract 32, then multiply by 5/9. Example: 98.6°F = (98.6−32) × 5/9 = 37°C. °C to °F: multiply by 9/5, then add 32. Example: 100°C = (100 × 9/5) + 32 = 212°F. Quick mental shortcuts: 0°C = 32°F (freezing); 100°C = 212°F (boiling); 37°C = 98.6°F (body temperature); −40 is where both scales meet. For rough estimates, double the Celsius value and add 30.
What is the difference between mass and weight? +
Mass is the amount of matter in an object (kilograms in SI) — it doesn't change regardless of location. Weight is a force: mass × gravitational acceleration (measured in Newtons). An astronaut who weighs 180 lbs on Earth weighs about 30 lbs on the Moon but has the same mass either way. In everyday life, we use “weight” to mean mass. But in science, baking, and medication dosing, using mass (kg/g) is more accurate than force-based weight.
Why does the US still use imperial units? +
The US actually legally adopted the metric system in 1866 and mandated federal agencies use it in 1992, but consumer adoption stalled. Key barriers: massive infrastructure investment in imperial-based systems, public unfamiliarity, industry lobbying (construction, automotive), and the cost of complete industrial retooling. The US uses metric behind the scenes — pharmaceuticals, military, science, and international trade all use metric. Road signs and popular culture remain the most visible holdouts of imperial measurement.
How do I convert area and volume units? +
Area and volume conversions require squaring or cubing the linear conversion factor. If 1 foot = 0.3048 meters, then 1 square foot = 0.3048² = 0.0929 m², and 1 cubic foot = 0.3048³ = 0.0283 m³. Common pitfall: applying the linear factor to area/volume calculations. For quick reference: 1 acre = 43,560 sq ft = 0.405 hectares; 1 US gallon = 3.785 liters; 1 cubic yard = 27 cubic feet = 0.765 m³.
What is the difference between US and UK/Imperial gallons? +
A US gallon = 3.785 liters. An Imperial (UK) gallon = 4.546 liters — about 20% larger. Similarly, a US fluid ounce = 29.57 mL vs. a UK fluid ounce = 28.41 mL. This creates confusion in cooking recipes online — always check whether a recipe uses US or UK measurements. The difference in fuel economy (mpg) between US and UK cars is largely due to this difference: a UK car "getting 40 mpg" actually uses less fuel than a US car getting 40 mpg, since the UK gallon is larger.