Convert 81 units in 12 categories: speed (km/h to mph), cups to ml, pressure (bar to psi), energy, frequency, temperature and data. Bilingual, works offline.
A recipe calls for 180 ml of milk, the label says 1 cup, and the two numbers are 56 ml apart. The same happens with a tyre pressure in psi when the manual gives bar, or with a drive in gigabytes when the box says terabytes. Every one of those mismatches is a conversion someone has to do, and doing it by hand means looking up a formula and hoping you did not get the factor backwards.
This converter puts twelve categories and 77 units on one screen so those lookups happen in the same place. The arithmetic is not where the difficulty usually lies.
A mile is defined as exactly 1.609344 kilometres, and a foot as exactly 0.3048 metres, so those conversions have no rounding in them. 100 km/h is 62.1372 mph. A knot is a nautical mile per hour, which is 1.852 km/h exactly, and it is not the same as a mile per hour: at 20 knots a ship is doing 37.04 km/h, not 32.19. Sailors, pilots and anyone reading an aviation forecast needs that distinction to be visible.
A US cup is 236.588 millilitres, a tablespoon is 14.7868 ml and a teaspoon is 4.92892 ml. Those numbers are not arbitrary: the tablespoon is defined as half a fluid ounce, the fluid ounce as about 29.5735 ml and the cup as 8 fluid ounces, which is why a cup is exactly 16 tablespoons and 3 teaspoons. British cups are 284.13 ml, a difference of about 20 percent. A cake that rises differently in London than in Los Angeles is usually not a different oven but a different cup.
One bar is exactly 100,000 pascals and one standard atmosphere is 101,325 pascals. Since one pound per square inch is 6,894.757 pascals, 1 bar works out at 14.5038 psi, and the 32 psi a typical car tyre is inflated to is 2.206 bar. Torr and millimetres of mercury are the same unit under two names, both 133.322 pascals, which is why 760 torr equals one atmosphere. They appear separately in the selector here because a recipe and a barometer use the names differently.
Both answers are correct for a different unit. KB, MB and GB are SI units with base 1000, so 1 KB is 1000 bytes. KiB, MiB and GiB are IEC units with base 1024, so 1 KiB is 1024 bytes. Nobody made a mistake; two standards ended up in use.
It explains a puzzle everyone hits. A drive advertised as 1 TB reports about 931 GB in Windows. The manufacturer counted 1,000,000,000,000 bytes and the operating system divides by 1,073,741,824 instead, so the same drive is 931 gibibytes. The gap is about 9.7 percent, which is enough to make people think something is missing. This converter carries both sets of units rather than picking one.
Every other conversion is a multiplication by a fixed factor. Temperature is not, because the scales are offset as well as scaled. Fahrenheit is defined so that water freezes at 32 and boils at 212, while Celsius uses 0 and 100, which forces an offset into any conversion between them. A calculator that treats this as a factor ratio gets it wrong, which is why 0 °C has to come out as 32 °F and not 0.
It does not convert currencies. Exchange rates change daily, and a rate frozen into a page would give confidently wrong numbers, which is worse than giving none. Everything else is computed in your browser, nothing is sent anywhere, and the page keeps working with the network off.
Unit Converter is a progressive web app. Install it from your browser and it runs like a normal app, with its own icon and its own window.
Open Unit Converter in Chrome, tap the browser menu (⋮) and choose “Install app” or “Add to Home screen”.
Open Unit Converter in Safari, tap the Share button and choose “Add to Home Screen”.
Open Unit Converter in Chrome, Edge or Brave and click the install icon on the right side of the address bar.
Convert 81 units in 12 categories: speed (km/h to mph), cups to ml, pressure (bar to psi), energy, frequency, temperature and data. Bilingual, works offline.
Yes. Unit Converter is a free, ad-free progressive web app. It needs no sign-up and no payment details, and your data stays on your own device.
Yes. Once installed as a PWA, Unit Converter runs from your device and keeps working when you have no internet connection.
Open Unit Converter in your browser and choose “Install app” from the Chrome menu, or “Add to Home Screen” in Safari. It then opens with its own icon, like a native app.
Unit Converter works on Android, iOS, Windows, macOS and Linux, because it is a progressive web app.
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