Unit Converter
Convert between metric and imperial units in seconds. Use the quick converter below, or jump straight to a specialised tool: recipes, body measurements, DIY work, temperature, or scientific units.
The Anglo-Saxon inch was once defined as the length of three dry, round barleycorns laid end to end. The modern inch is now exactly 25.4 mm by international agreement — barley no longer involved.
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Frequently asked questions
How accurate are the conversions?
All conversions use the internationally agreed conversion factors — for example, 1 inch is exactly 25.4 millimetres and 1 pound is exactly 0.45359237 kilograms. Results are rounded to a sensible number of decimals for display but the underlying calculation uses full double-precision arithmetic.
What is the difference between the metric and imperial systems?
The metric system uses base-ten units (millimetres, metres, kilometres; grams, kilograms; degrees Celsius). The imperial system, still used in everyday measurement in the United States and parts of the United Kingdom, uses inches, feet, miles; ounces, pounds; and degrees Fahrenheit. Most of the world has standardised on metric for science and trade.
How do I convert between Celsius and Fahrenheit?
To convert Celsius to Fahrenheit, multiply by 9/5 and add 32. To convert Fahrenheit to Celsius, subtract 32 and multiply by 5/9. So 100 °C is 212 °F (boiling point of water) and 0 °C is 32 °F (freezing point of water).
Do you have a converter optimised for cooking?
Yes — the recipe converter handles cup-to-gram conversions for around twenty common ingredients (flour, sugar, butter, oil, etc.) using their actual densities, plus a paste-a-recipe mode that converts an entire ingredient list at once. The body converter does height plus weight together for fitness tracking, and the DIY converter accepts fractional and mixed-unit input like 5 feet 10 inches or 1 1/4 inches.
Do you support scientific units for school work?
Yes — the scientific converter at /science covers energy (joules, calories, electronvolts, kWh), force (newtons, dynes, lbf, kgf), pressure (pascals, atmospheres, bar, mmHg, psi), power (watts, horsepower), speed (m/s, km/h, mph, knots, even the speed of light), area (m², ft², acres, hectares), and time (microseconds to Julian years). Scientific notation input like 1.5e-19 is handled natively and the result switches to exponential form automatically when fixed-point would be unreadable.
Why use this converter instead of just searching Google?
Both work. This site is faster for repeated conversions — pick a category once and tweak units freely — and it works without sending each individual conversion as a search query. There is no sign-up and no tracking beyond standard analytics. Your last-used unit pair is remembered locally so the page is preconfigured next time you visit.
Can I use this converter offline?
Once the page is loaded, the conversion runs entirely in your browser and does not need a network connection. The site also ships a web app manifest so you can install it to your phone home screen on iOS and Android for quick access.