TOOL 02 / UNITS

An engineering unit converter that reads whole expressions.

Q: How do I convert compound units?

Type the value with its units, then to and the units you want, for example 60 mi/h to km/h. Use / for “per”, ^ for powers and a space or * between units that are multiplied.

Q: Can I use the result in a calculation?

Yes. The calculator converts inline with the same to, and values on a worksheet keep their units from card to card.

Pick a quantity and see every unit of it at once. Or write a calculation with units in it and say what you want it in.

Open the unit converter — Free ↗What it does ↓

No account required · Right in your browser · Works offline once opened

The Slide Rule unit converter showing one atmosphere in thirteen pressure units, and 60 miles per hour converted to 96.56064 kilometres per hour — One atmosphere in every pressure unit at once and, on the right, a compound conversion typed as a sentence.

WHAT IT DOES

Two ways to convert.

A table for when you know the quantity, and a line to type into for everything else.

Every unit at once

Choose a quantity, enter a value and the unit it is in, and the whole family updates together. There is no “to” box to keep changing.

Convert any expression

Write a quantity, then to and the unit you want. Compound units are fine: 60 mi/h to km/h, 1 cP to Pa s, 3000 rpm to rad/s.

Calculate, then convert

The line takes arithmetic too. 70 kg * 9.81 m/s^2 to kN multiplies a mass by an acceleration and gives 0.6867 kN.

SI and US customary

Metres and feet, newtons and pounds-force, pascals and psi, joules and BTU, with the engineering sizes in between: kN, MPa, GPa, ksi, kip.

The same units everywhere

The calculator and the worksheet understand the same units, so 200 GPa to ksi works there as well, and a worksheet card can end in to mm.

Nothing to sign up for

The converter is part of the free plan and needs no account. Opened once, it keeps working offline.

TRY THESE

Conversions people look up.

Typed into “Convert any expression” exactly as shown.

YOU TYPESLIDE RULE ANSWERSWHAT IT IS
60 mi/h to km/h96.56064 km/hSpeed, miles per hour to kilometres per hour.
1 atm to psi14.69594878 psiPressure, a standard atmosphere in pounds per square inch.
200 GPa to ksi29007.54755 ksiThe elastic modulus of steel, in US customary units.
350 hp to kW260.994955 kWPower, horsepower to kilowatts.
2.5 kWh to MJ9 MJEnergy, kilowatt-hours to megajoules.
300 K to degC26.85 °CTemperature, kelvin to degrees Celsius.
1 cP to Pa s0.001 Pa·sViscosity, centipoise to pascal-seconds.
3000 rpm to rad/s314.1592654 rad/sAngular speed, revolutions per minute to radians per second.

WHAT IS COVERED

Nineteen kinds of quantity.

The quantities an engineering or science course keeps coming back to, each with the units you meet in textbooks, datasheets and older references.

Converting between quantities that do not match, such as a force to a pressure, gives a message rather than a wrong number.

MECHANICS

Lengthm, mm, µm, in, ft, mi …
Masskg, g, lb, slug, tonne …
Times, ms, min, h, day …
Speedm/s, km/h, mph, knot …
Accelerationm/s², ft/s², g₀
ForceN, kN, lbf, kip, kgf …
TorqueN·m, kN·m, lbf·ft, lbf·in
Angle°, rad, grad, rev …
Angular speedrad/s, rpm, °/s
FrequencyHz, kHz, MHz, GHz

MATERIALS, FLUIDS AND ENERGY

PressurePa, MPa, bar, atm, psi, ksi, mmHg …
EnergyJ, kJ, kWh, cal, BTU, eV …
PowerW, kW, MW, hp, BTU/h
Temperature°C, K, °F, °R
Densitykg/m³, g/cm³, lb/ft³ …
ViscosityPa·s, mPa·s, poise, cP
Flow ratem³/s, L/s, L/min, gal/min …
Aream², mm², ha, ft², acre …
Volumem³, L, mL, ft³, US gal …

QUESTIONS

Before you open it.

How do I convert compound units?

Type the value with its units, then to and the units you want, for example 60 mi/h to km/h. Use / for “per”, ^ for powers and a space or * between units that are multiplied.

How do I convert temperatures?

Choose Temperature in the table for °C, K, °F and °R side by side, or type 300 K to degC. The offset between the scales is handled for you.

How many digits does it give?

Up to ten significant figures, so that a converted value can go straight back into a calculation without losing accuracy. Round it for your final answer.

Can I use the result in a calculation?

Yes. The calculator converts inline with the same to, and values on a worksheet keep their units from card to card.

One of eight tools that work together.

A value from one goes straight into another

NOTHING TO INSTALL

The right units, every time.

Open the unit converter — Free ↗

No account required. Free for every tool; Pro adds unlimited worksheets and exports.