Unit converter

Convert between units in 13 categories, from length and pressure to data size and fuel economy, with swap and copy. Up to 6 decimals.

Length · m → km0.001 km

What to know

The unit converter holds 13 categories in one form: length, weight, temperature, area, volume, speed, pressure, energy, power, angle, time, data and fuel efficiency. On the root page a Category select switches between them, and each category also has its own page with the category fixed.

Most categories convert through a base unit. A value is multiplied by the factor of the From unit and divided by the factor of the To unit, so 5 mi to km is 5 x 1609.344 / 1000 = 8.04672. Temperature and fuel efficiency are the exceptions because they use offsets and reciprocals instead of a single factor.

Results show up to 6 decimal places, and anything smaller than 0.000001 switches to scientific notation with 6 significant digits. The Swap units button exchanges From and To in one click, and a value that overflows the supported range triggers an error instead of a number.

Inputs are validated as you type. Temperature cannot go below absolute zero, fuel efficiency must be greater than zero, and anything that is not a number is flagged. The converter handles physical units only, with no currency or exchange rate lookups.

Typed numbers are read with the conventions of the page language, so a Spanish visitor can enter 12,5 where an English one enters 12.5. The Value label always names the From unit, which makes it easy to confirm that a number is read in the unit you intended before you copy it.

Choose a specific task 13
Related tools 1
How to use Unit converter
  1. Choose a Category such as Length, or open the dedicated category page.
  2. Type 5 in the Value field and pick mi in From and km in To.
  3. The Result line shows 8.04672 km.
  4. Press Swap units to see 8.04672 km turned back into 5.000000 mi, then copy the result.

Quick answers

How many decimals does the result show?

Up to 6. Values below 0.000001 appear in scientific notation, for example 1.5e-7.

Which units are not included?

Nautical miles, stones, torr, BTU, bits, terabytes and calendar months or years are absent, because each category carries a fixed list of the most common units.

Why does temperature reject my number?

The page blocks values below absolute zero: -273.15 C, -459.67 F or 0 K.

Does the converter use live data?

No. All factors are constants in the page, so the same input always gives the same output without a network request.