Unit Converter
Convert between length, weight, and temperature units — metric and imperial.
Popular conversions
How to use the Unit Converter
- Choose Length, Weight, or Temperature as the conversion category.
- Type the amount into Value, then pick the unit you have in From and the unit you want in To.
- The result updates as you type. Use Swap units to reverse the direction, or tap one of the popular conversions to load that pair instantly.
About the Unit Converter
This unit converter handles the three categories of conversion people need most often: length (meters, feet, inches, kilometers, miles, and more), weight (kilograms, pounds, ounces, grams), and temperature (Celsius, Fahrenheit, Kelvin). Pick a category, choose your 'from' and 'to' units, and the result updates instantly as you type.
It's designed for quick everyday conversions — following a recipe written in another country's units, converting your height or weight for a form, or checking a temperature reading — without needing to remember or look up conversion factors.
Worked example
Example: converting temperature, 100°F converts to approximately 37.8°C — useful for reading a US-style thermostat or weather report if you think in Celsius.
How the conversions are calculated
Every length is converted through meters, every weight through kilograms, and every temperature through degrees Celsius, so any pair of units in a category uses the same exact definitions. Those definitions are fixed by international agreement rather than measured: an inch is exactly 2.54 cm, a foot exactly 0.3048 m, a yard 0.9144 m, and a mile 1,609.344 m. A pound is exactly 0.45359237 kg, an ounce is 1/16 of a pound (about 28.35 g), and a stone is 14 pounds (about 6.35 kg). Results are shown to at most four decimal places.
Temperature is different from length and weight
Length and weight conversions are pure multiplication, but temperature scales also have different zero points, which causes two common errors. First, a temperature difference converts without the offset: a rise of 10 °C is a rise of 18 °F, not 50 °F. Second, doubling a temperature means nothing physically unless you use Kelvin, the scale that starts at absolute zero (0 K = −273.15 °C). One curiosity: −40 is the same reading on both the Celsius and Fahrenheit scales.
Shortcuts for estimating in your head
- Kilometers to miles: multiply by 0.6 (or by 5/8). A 10 km race is about 6.2 miles.
- Kilograms to pounds: multiply by 2.2. 70 kg is about 154 lb.
- Centimeters to inches: divide by 2.5 for a quick estimate, 2.54 for the exact answer.
- Celsius to Fahrenheit: double it and add 30. It's close in everyday ranges (20 °C → about 70 °F; exact is 68 °F) and drifts further off at the extremes.
- Watch for volume: US and UK gallons, pints, and fluid ounces are different sizes, which is a frequent source of recipe errors. This converter covers length, weight, and temperature only.
Frequently asked questions
- What unit categories does this converter support?
- Length (millimeters to miles), weight/mass (grams to pounds), and temperature (Celsius, Fahrenheit, and Kelvin). Switch categories using the selector above the converter.
- Are the conversions precise?
- Yes, conversions use standard, internationally recognized conversion factors (for example, 1 inch = 2.54 cm exactly) and display results rounded to a reasonable number of decimal places for readability.
- Why is Fahrenheit to Celsius not a simple ratio?
- Celsius and Fahrenheit scales have different zero points as well as different degree sizes, so the formula is °C = (°F − 32) × 5/9 rather than a simple multiplication.
- Can I convert both directions?
- Yes — swap the 'from' and 'to' units at any time, or use the swap button, and the converter recalculates instantly in the reverse direction.