All-in-One Unit Converter (length, weight, volume, temperature & more)

Understanding the all-in-one unit converter — concept and principle

This converter handles everyday and technical units in one place: length, area, volume, mass, temperature, speed, time, data, pressure, energy and power. Pick a "from" unit and a "to" unit of the same kind, enter a value, and it shows the result plus how much one unit of each equals in the other. Students, travellers, cooks, engineers and anyone reading foreign specifications use it.

Through a base unit — with the default inputs: 3.048 m.

How it is calculated

Each unit is stored as an exact factor to one base unit for its kind: metre, square metre, litre, kilogram, kelvin, metre per second, second, byte, pascal, joule or watt.
Result = value × factor of "from" unit ÷ factor of "to" unit.
Temperatures also shift by their zero point: K = °C + 273.15; °F is converted through the Rankine scale, with °R = °F + 459.67 and K = °R × 5/9.
Only units of the same kind can be converted. Results show up to 10 significant digits.

The principle

Converting through a single base unit means every pair of units uses the same two exact factors, so there is no rounding chain. Most factors are exact by definition: since 1959 the international inch is exactly 25.4 mm, so the foot is 0.3048 m and the pound 0.45359237 kg. Data units follow IEC 80000-13: a kilobyte is 1,000 bytes while a kibibyte is 1,024 bytes. Korean traditional units are included: 1 pyeong = 400/121 m² (about 3.3058 m²) and 1 don = 3.75 g. Temperature is different from other quantities because the scales have different zero points, so a simple ratio does not work; that is why the "1 unit equals" rows are blank for temperature.

Worked example

Default: 10 feet to metres.

Factor for the foot = 0.3048 m; factor for the metre = 1.
Result = 10 × 0.3048 ÷ 1 = 3.048 m; quantity: Length.
1 ft = 0.3048 m.
1 m = 1 ÷ 0.3048 = 3.280839895 ft.

Each point is the calculator re-run with only “Value” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Value	Result
2.5	0.762 m
5	1.524 m
7.5	2.286 m
10	3.048 m
12.5	3.81 m
15	4.572 m
20	6.096 m

How to read the result

Check that the quantity matches what you meant: US and UK gallons differ by about 20%, and a US cup is not the same as a metric cup of 250 mL. For data sizes, operating systems and storage makers sometimes use different prefixes, which explains why a "1 TB" drive shows fewer "GB". For cooking, small rounding is harmless; for engineering, keep enough significant digits.

Common mistakes

Mixing US and UK gallons or fluid ounces.
Treating a temperature difference like a temperature: a change of 10 °C is a change of 18 °F, not 50 °F.
Confusing kB (1,000 B) with KiB (1,024 B).
Using calorie and kilocalorie interchangeably; food "Calories" are kilocalories.

Keep in mind: Results are exact to the factors listed, but rounding for display can matter in precision work. For trade, medicine and engineering, use the units and tolerances your regulations require.

Frequently asked questions

How many feet are in a metre?

About 3.2808, because one foot is exactly 0.3048 m.

Why can't I convert kilograms to litres?

They measure different quantities, mass and volume. You need the substance's density.

What is a pyeong?

A traditional Korean area unit of 400/121 m², about 3.3058 m², still used for flats and land.

Sources: BIPM, The International System of Units (SI Brochure), 9th ed. (2019) · NIST Special Publication 811 (2008), Appendix B; NIST Handbook 44, Appendix C · IEC 80000-13, Quantities and units — Information science and technology

Checked 9 Nov 2026. SI Brochure (BIPM, 9th ed., 2019); NIST SP 811 (2008), Appendix B; US customary volumes from NIST Handbook 44, Appendix C; data units per IEC 80000-13 (kB = 1,000 B, KiB = 1,024 B); traditional Korean units 1 pyeong = 400/121 m² and 1 don = 3.75 g.

Your numbers