How this unit converter works
Most units in a category are related by a fixed ratio, so converting is simply multiplication. Internally each category has a base unit — metres for length, kilograms for weight, litres for volume, and so on. Every unit stores how many base units it represents, so the converter first turns your value into the base unit, then divides by the target unit's factor.
For example, length uses metres as the base: a kilometre is 1000 m, a mile is 1609.344 m, a foot is 0.3048 m. To convert miles to kilometres the tool multiplies by 1609.344 to reach metres, then divides by 1000 — which is why 1 mile = 1.609 km. Temperature is the exception: Celsius, Fahrenheit and Kelvin have different zero points, so the converter uses formulas rather than a single multiplier.
Reference note: volume and weight use US customary units (US gallon ≈ 3.785 L, pound = 16 oz). Data sizes use binary multiples (1 KB = 1024 bytes). Results are rounded to a sensible number of significant figures for display.
Common conversions at a glance
| From | To | Multiply by |
|---|---|---|
| Miles | Kilometres | 1.609344 |
| Kilometres | Miles | 0.621371 |
| Pounds | Ounces | 16 |
| Kilograms | Pounds | 2.204623 |
| Inches | Centimetres | 2.54 |
| km/h | mph | 0.621371 |
| US gallons | Litres | 3.785412 |
| Cups (US) | Millilitres | 236.588 |
Frequently asked questions
- How many kilometers in a mile?
- One mile equals 1.609 kilometres (precisely 1.609344 km), and one kilometre is about 0.621 miles. Select Length, set From to miles and To to kilometres, and enter your value.
- How do I convert Celsius to Fahrenheit?
- Multiply the Celsius value by 9/5 and add 32. So 20 °C × 1.8 = 36, plus 32 = 68 °F. Temperature uses formulas, not a single multiplier, and this converter handles C, F and K automatically.
- How many ounces in a pound?
- There are 16 ounces in one pound (avoirdupois), so 2 pounds is 32 ounces. Choose Weight / Mass, set From to pounds and To to ounces.
- How many milliliters in a cup?
- This tool uses the US cup of about 236.588 ml. A metric cup is 250 ml and a UK cup is roughly 284 ml, so check which standard your recipe assumes.
- How do I convert km/h to mph?
- Divide the km/h value by 1.609 (or multiply by 0.621). So 100 km/h is about 62.1 mph. Select Speed, set From to km/h and To to mph.
- Is a US gallon the same as a UK gallon?
- No — a US gallon is about 3.785 litres while a UK (imperial) gallon is about 4.546 litres, roughly 20% larger. This converter uses US customary gallons, quarts, pints, cups and fluid ounces.