Free Unit Converter
Convert across 16 categories — length, weight, temperature, volume, area, speed, time, data, angle, pressure, energy, power, force, frequency, fuel economy, and cooking. Pin favorite pairs for one-click access. Accurate to 10+ significant digits using internationally standardized definitions.
- Nanometer999,999,999,999.9999 nm
- Micrometer1,000,000,000 µm
- Millimeter1,000,000 mm
- Centimeter100,000 cm
- Meter1,000 m
- Kilometer1 km
- Inch39,370.07874 in
- Foot3,280.839895 ft
- Yard1,093.613298 yd
- Mile0.621371 mi
- Nautical mile0.539957 nmi
- Light year1.057004e-13 ly
Tips
- 16 categories: length, weight, temperature, volume, area, speed, time, data, angle, pressure, energy, power, force, frequency, fuel economy, and cooking.
- Live conversion: change category, units, or value and everything updates immediately.
- All units at once: the list shows every unit in the category — copy any with one click.
- Save pairs: star any conversion to keep it pinned across sessions.
- Precision slider: 0-10 decimal places, auto-switch to scientific for huge/tiny values.
Common conversions at a glance
| From | To | Formula |
|---|---|---|
| Kilometers | Miles | km × 0.621371 |
| Inches | Centimeters | in × 2.54 |
| Pounds | Kilograms | lb × 0.453592 |
| Celsius | Fahrenheit | C × 9/5 + 32 |
| Liters | US Gallons | L × 0.264172 |
| Square meters | Square feet | m² × 10.7639 |
| km/h | mph | km/h × 0.621371 |
When you need a unit converter
Travel
Convert km to miles, kg to lbs for luggage, and Celsius to Fahrenheit when reading weather abroad.
Cooking
Convert ounces to grams, cups to milliliters, and Fahrenheit oven temperatures to Celsius.
Fitness
Convert body weight, running distance, and gym plate weights between metric and imperial systems.
Engineering and DIY
Convert millimeters to inches for hardware, square meters to square feet for flooring estimates.
Frequently asked questions
Why don't temperatures convert linearly like other units?
Temperature scales have different zero points. Celsius zero is the freezing point of water; Fahrenheit zero is much colder; Kelvin zero is absolute zero. So converting requires both a multiplication and an offset: F = C × 9/5 + 32, K = C + 273.15.
Is 1 kg exactly 2.2 lbs?
Not exactly. 1 kg = 2.20462262 lbs. The '2.2' figure is a quick mental shortcut used in everyday conversions. This tool uses the full precision.
What is the difference between a US gallon and an Imperial gallon?
A US gallon is 3.785 liters. An Imperial (UK) gallon is 4.546 liters — about 20% larger. This is a common mistake when converting fuel economy figures between countries.
Can I convert currencies here?
No. Currency conversion requires live exchange rate data and is a separate tool. This converter handles physical units only.
How precise are the conversions?
All conversions use internationally standardized SI definitions with full double-precision floating-point math. Results are accurate to at least 10 significant digits — more than enough for engineering, cooking, fitness, and everyday use.
Other free tools
Convert length, weight, temperature, volume, area, and time across 50+ units. Live, with formula display for learning purposes.
How to use
- 1Pick the conversion category (Length / Weight / Temperature / etc.).
- 2Pick source and destination units.
- 3Enter the value — destination updates live.
- 4See the conversion formula below for reference.
Why use this tool
- Six categories, 50+ units total.
- Formula display — learn the math, not just the answer.
- Browser-only — works offline.
Real-world examples
Recipe conversion
American recipe says 350°F → convert to 177°C for European oven. Or 1 cup → 240 ml.
Distance for travel
Walking guidebook in km → convert to miles for US trip planning.
Engineering
PSI ↔ kPa, lb-ft ↔ Nm — between imperial and metric for every category.