How to use it
Choose what you're measuring (length, weight, area…), type a value, and pick the unit you're starting from and the unit you want. The answer updates as you go, and the ⇄ button swaps the two units.
Below the answer you'll see the conversion factor (how many of the new unit fit in one of the old unit) and the multiplication or division that gets you there. The factors are exact: an inch is defined as exactly 2.54 cm, and a mile is exactly 1609.344 m. When an answer would have endless decimals, it's rounded, and the \(\approx\) sign tells you so.
Converting by hand
Multiply by a fraction equal to 1, with the unit you want on top and the unit you're getting rid of on the bottom. To change 26.2 miles to kilometers:
\[26.2\ \text{mi} \cdot \frac{1.609344\ \text{km}}{1\ \text{mi}} \approx 42.16\ \text{km}\]
The miles cancel and kilometers are left, which is a quick way to check you didn't flip the factor.
Metric steps, area and volume
- Metric length and mass units step by 10, so converting is just moving the decimal point: \(3.5\ \text{km} = 3500\ \text{m}\).
- For area, square the factor: a foot is 12 inches, so a square foot is \(12 \cdot 12 = 144\) square inches.
- For volume, cube it: a cubic yard is \(3 \cdot 3 \cdot 3 = 27\) cubic feet.
Temperature is the one exception, because the scales don't start at the same zero. To go from Celsius to Fahrenheit, multiply by \(\frac{9}{5}\) and add 32, so \(20\ ^\circ\text{C} = 68\ ^\circ\text{F}\).