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How Unit Conversion Works
Unit conversion uses fixed ratios between measurement systems. Our converter handles 7 categories with dozens of units, converting instantly as you type. Temperature uses special formulas (not simple ratios), and all conversions happen in your browser.
How to Use This Converter
- Select a category by clicking one of the tabs at the top: Length, Weight, Temp, Area, Volume, Speed, or Data. Each category loads its own set of units into the "From" and "To" dropdown menus.
- Choose your units. Use the "From" dropdown to select the unit you are converting from, and the "To" dropdown to select the unit you want to convert to. Click the "Swap" button to quickly reverse the direction of conversion.
- Enter your amount in the number field. The result updates instantly as you type, so you can experiment with different values without pressing any button.
- Copy the result by clicking the "Copy" button. This copies the full conversion summary, including both units and the result, to your clipboard.
How It Works
Most unit conversions rely on fixed conversion factors. The converter first translates the input amount into a standard base unit for each category, such as metres for length, grams for weight, or square metres for area. It then divides by the conversion factor of the target unit to produce the final result. For example, converting 5 miles to kilometres involves multiplying 5 by the mile-to-metre factor (1609.344) to get 8046.72 metres, then dividing by the kilometre-to-metre factor (1000) to arrive at 8.04672 km. Temperature is the exception because it uses offset formulas rather than simple ratios. To convert Celsius to Fahrenheit, the calculator multiplies by 9/5 and adds 32. To convert Fahrenheit to Celsius, it subtracts 32 and multiplies by 5/9. Kelvin conversions add or subtract 273.15 from the Celsius value. All calculations run entirely in your browser using JavaScript, ensuring privacy and zero server delay.
Common Conversions Reference
| From | To | Factor |
|---|---|---|
| 1 inch | 2.54 cm | Length |
| 1 foot | 30.48 cm | Length |
| 1 mile | 1.609 km | Length |
| 1 pound | 453.6 g | Weight |
| 1 stone | 6.350 kg | Weight |
| 1 ounce | 28.35 g | Weight |
| 0 °C | 32 °F | Temp |
| 100 °C | 212 °F | Temp |
| 1 UK gallon | 4.546 litres | Volume |
| 1 US gallon | 3.785 litres | Volume |
Frequently Asked Questions
How many centimetres are in an inch?
One inch is exactly 2.54 centimetres. This conversion factor was internationally agreed upon in 1959 and is used across engineering, manufacturing, and everyday measurement. To convert inches to centimetres, multiply the number of inches by 2.54. To go the other way, divide the centimetre value by 2.54 to get inches.
How do I convert Celsius to Fahrenheit?
To convert Celsius to Fahrenheit, multiply the Celsius temperature by 9/5 (or 1.8) and then add 32. For example, 20 degrees Celsius equals (20 times 1.8) plus 32, which is 68 degrees Fahrenheit. To convert Fahrenheit back to Celsius, subtract 32 from the Fahrenheit value and multiply by 5/9. This formula accounts for the different zero points and scale sizes of the two systems.
How many grams are in a pound?
One pound equals exactly 453.592 grams. This is the avoirdupois pound used in everyday commerce in the UK and US. To convert pounds to kilograms, divide by 2.205 (or multiply by 0.4536). When following recipes or tracking dietary intake, knowing this conversion helps you switch seamlessly between metric and imperial weight measurements.
How many miles are in a kilometre?
One kilometre equals approximately 0.621371 miles, and conversely one mile equals approximately 1.60934 kilometres. A handy approximation is that 5 miles is roughly 8 kilometres, or you can multiply kilometres by 0.6 for a quick mental estimate. This conversion is essential when driving in countries that use different distance units on their road signs.
What is the difference between a UK gallon and a US gallon?
A UK (imperial) gallon is 4.546 litres, while a US gallon is only 3.785 litres. This means a UK gallon is about 20% larger than a US gallon. The difference is important when comparing fuel economy figures or following recipes from different countries. Always check which gallon standard is being referenced to avoid measurement errors.
What is the difference between metric and imperial units?
The metric system, also called SI (International System of Units), is based on powers of 10 and uses units like metres, grams, and litres. The imperial system, still common in the UK and US for some measurements, uses units like feet, pounds, and gallons. Metric is simpler for scientific work because conversions involve multiplying or dividing by 10, 100, or 1000. Imperial units have irregular conversion factors, which is why a converter tool is so helpful.
