Convert length, weight, temperature, volume, area, speed, and data — instantly.
Unit Converter converts between units across all common measurement categories: length (mm, cm, m, km, inches, feet, yards, miles), weight/mass (mg, g, kg, lb, oz, ton), temperature (Celsius, Fahrenheit, Kelvin), volume (mL, L, fl oz, cups, pints, quarts, gallons), area, speed, time, data storage, and pressure. Enter a value in any field and all equivalent values update instantly.
Unit conversion is a daily practical need: following a recipe that uses cups when you have grams, understanding a temperature in Fahrenheit when you think in Celsius, calculating fuel efficiency in km/L vs mpg, or converting between metric and imperial units when reading international specifications. This tool handles all of these without manual formula lookup.
The metric system (SI) is the international standard used by science, medicine, and most of the world. The United States, Liberia, and Myanmar use the imperial system (inches, pounds, Fahrenheit) alongside the metric system in scientific contexts. Engineering and international trade frequently require converting between systems — a single unit error caused NASA's Mars Climate Orbiter spacecraft to be lost in 1999 (the navigation team mixed metric and imperial units).
Body temperature 98.6°F to Celsius
Result: 98.6°F → (98.6 - 32) × 5/9 = 37.0°C — normal human body temperature
5 miles to kilometers
Result: 5 miles × 1.60934 = 8.047 km — useful for running distances and road trips
2 cups to milliliters
Result: 2 cups × 236.588 mL = 473.18 mL — for recipe conversions between US and metric
Why does the US still use imperial units?
The US has made several attempts to fully metricate. The Metric Conversion Act of 1975 made metric the preferred system but voluntary. Industries that went metric (pharmaceuticals, science, military) did so for practical reasons. Everyday consumer life (road signs, food labels, construction) remains largely imperial due to infrastructure costs and consumer habit.
What is the difference between mass and weight?
Mass is the amount of matter in an object (measured in kg or lb_mass). Weight is the gravitational force on that mass (measured in Newtons). In everyday usage they are treated as equivalent on Earth. In space or on other planets, your mass stays the same but your weight changes. Scales typically measure weight but display in mass units assuming Earth gravity.
How do I convert Fahrenheit to Celsius?
Formula: C = (F - 32) × 5/9. Celsius to Fahrenheit: F = C × 9/5 + 32. Quick mental estimate: subtract 32, then halve the result (this gives 5/10 instead of 5/9, about 11% error, good enough for weather). Exact: 32°F = 0°C, 212°F = 100°C, 98.6°F = 37°C.
What is the difference between US and UK fluid ounces?
US fluid ounce = 29.5735 mL. UK/Imperial fluid ounce = 28.4131 mL. A US cup = 8 US fl oz = 236.6 mL; a UK cup = 10 UK fl oz = 284.1 mL. US and UK pints and gallons also differ significantly. This tool defaults to US fluid measurements; specify UK when needed.
What is a troy ounce and why does it matter?
A troy ounce (ozt) = 31.1035g, used exclusively for precious metals (gold, silver, platinum). A standard (avoirdupois) ounce = 28.3495g. When buying gold, prices are per troy ounce — a 1-ounce gold bar is 31.1g, not 28.3g. The troy system dates to medieval European trade fairs and persists in commodity markets worldwide.