Unit Converter

How to use

1. Pick a category chip, or type a whole sentence such as 180 lb in kg into Ask for it and press Enter.
2. Type the value, set From and To, and read the answer above; the swap icon between the menus reverses the pair.
3. Leave Show on Meaningful for every digit, or pick 6 figures or 2 decimals to round, and read the cost on Digits shown.
4. Copy result takes the figure with its unit; Share link copies an address that reopens this exact conversion.

About this tool

Nineteen categories sit in one row of chips, from Length and Mass through Temperature, Volume, Area, Speed, Data, Time, Cooking, Pace and Fuel to the engineering set: Pressure, Energy, Power, Angle, Frequency, Force, Torque and Data transfer rate. Pick one, type a value, set From and To, and the answer above rewrites itself on every keystroke. The swap icon between the two menus flips the direction without retyping. If you would rather say it than click it, type 180 lb in kg into Ask for it and the chip, both menus and the value move to match, with the reading said back so you can correct it.

Every factor is the defining decimal, kept as a string and run as an exact fraction, so a conversion that ends prints every digit and is marked Exact: one mile is 1,609,344 mm, not 1,609,340. A ratio that never ends, kilometres to miles for one, prints fifteen significant digits and is marked Repeats. Only the radian is Rounded, because π has no end. The working sits on its own card, so the claim can be checked rather than taken on trust.

Show chooses how much of that you see. Meaningful is every digit; 6 figures and 2 decimals round every figure on the page and the Digits shown card says what the rounding cost, as in 4 mm short of 1,609,344. Under the cards, the same quantity is listed in every other unit of the category, and the sixteen conversions people search for most, cm to inches through kilowatts to horsepower, are a row of links that open their pair.

Names that mean two things are kept apart. The volume list carries US and imperial gallons, quarts, pints and fluid ounces beside each other, and the answer says which it holds; Data pairs the decimal gigabyte a drive is sold in with the binary gibibyte your system reports. Temperature carries both readings and differences, because a rise of 10 °C is a rise of 18 °F while a reading of 10 °C is 50 °F. The address bar keeps the category, both units, the value and the Show choice, so a pasted link opens on the same conversion.

Where it stops short

• No currencies. Exchange rates move all day and every factor here is fixed, so adding them would mean shipping numbers that go stale.
• Fifteen significant digits is where a repeating answer stops. That is past what any measurement carries, and the Exactness card says when an answer is cut there rather than ended.
• Cooking is volume against volume. Grams per cup depends entirely on whether the cup holds flour or sugar, so nothing here pretends to know.
• Running pace takes decimal minutes, not clock minutes. A 5:30 kilometer goes in as 5.5, and typing 5.30 gives you 5 minutes 18 seconds.