Unit Converter

What is Unit Converter?

The Unit Converter is a free online tool that converts measurements across fourteen physical categories: length, mass, temperature, area, volume, speed, pressure, energy, power, angle, data-transfer rate, fuel economy, frequency and time. Engineers, students, cooks, scientists and travelers use it to change kilometers to miles, kilograms to pounds, bar to psi, joules to calories, or watts to horsepower. Pick a category, type a value, and choose your From and To units — the result updates instantly, and a full results table shows the same value in every unit of that category at once. A swap button reverses the two units, a copy button sits on each row, and you can set how many significant figures every result is rounded to. Temperature and fuel economy use the correct non-linear formulas, and numbers are formatted for your locale.

How to use Unit Converter

1. Choose one of the fourteen categories from the segmented buttons: Length, Mass, Temp., Area, Volume, Speed, Pressure, Energy, Power, Angle, Data, Fuel, Freq. or Time.
2. Type the number you want to convert into the From value field.
3. Pick the source unit in the From dropdown and the target unit in the To dropdown; the converted result appears instantly.
4. Use the swap button to exchange the From and To units, and the copy button to copy the result.
5. Read the all-units table to see your value in every unit at once, copy any row, and open the settings gear to set the significant-figure precision.

Examples

Length, 1 km to m

1,000

Temp., 100 °C to °F

212

Pressure, 1 bar to psi

14.5038

Frequently asked questions

Which categories and units are supported?

Fourteen categories with expanded unit sets: Length (mm, cm, m, km, in, ft, yd, mi, nmi), Mass (mg, g, kg, t, oz, lb, st), Temperature (°C, °F, K), Area (mm², cm², m², km², ft², yd², ac, ha), Volume (ml, l, m³, tsp, tbsp, fl oz, cup, pt, qt, gal), Speed (m/s, km/h, mph, ft/s, knot), Pressure (Pa, kPa, MPa, bar, psi, atm, Torr), Energy (J, kJ, cal, kcal, Wh, kWh, eV, BTU, ft·lb), Power (W, kW, MW, hp, PS, BTU/h), Angle (°, rad, grad, arcmin, arcsec, turn), Data rate (bit/s, kbit/s, Mbit/s, Gbit/s, B/s, kB/s, MB/s, GB/s), Fuel economy (km/L, L/100km, mpg US, mpg UK), Frequency (Hz, kHz, MHz, GHz, rpm) and Time (ms, s, min, h, day, week, month, year).

What does the all-units table show?

Below the converter, a table lists your input value converted into every unit of the chosen category at once. Each row is a read-only field you can copy with one click, and in the workspace each row is a separate output you can chain into another tool.

Can I swap the units and change the precision?

Yes. The swap button exchanges the From and To units in place, and the settings gear lets you choose how many significant figures every result is rounded to (3, 4, 6, 8 or 10). Both the converter result and the whole table update instantly.

Why do temperature and fuel economy convert differently from other units?

Temperature scales are non-linear and need offset formulas rather than a simple ratio, and fuel economy mixes distance-per-volume units (km/L, mpg) with a volume-per-distance unit (L/100km) that is reciprocal, so the tool applies the correct equations instead of a single multiplier.

Does my data get uploaded anywhere?

No. Every conversion runs 100% client-side in your browser with no upload and no server communication, so your values never leave your device.