Torque Calculator
Torque from a force on a lever (τ = F × r) or from power and rpm (P = τω): enter any two values to get the third, in N·m, kgf·m, lbf·ft or lbf·in.
Answer
τ = F × r (force at right angles to the arm)
- Given (in base units): F = 200 N, r = 0.3 m
- τ = F × r = 60 N·m
Values
Fill in any 2; leave the one to work out empty.
How is this calculated?
τ = F × r (force at right angles to the lever). P = τ × ω, with ω in rad/s; in workshop units, hp = lbf·ft × rpm ÷ 5,252 and kW = N·m × rpm ÷ 9,549.Runs in your browser — nothing you enter leaves this device.
About this tool
What it does
Torque Calculator works out turning force two ways. From a force on a lever: torque is the force times its distance from the axis, τ = F × r — how tight a wrench of a given length gets a bolt with a given push, or how hard you must push to reach a torque setting. From power and speed: power is torque times rotational speed, P = τ × ω — the torque of an engine or motor from its power and rpm, or its power from a torque figure. Choose which at the top, then enter any two of the three values; the third is worked out with the formula and working shown. Torque can be in newton metres, kilonewton metres, newton centimetres, kilogram-force metres, pound-force feet or pound-force inches; force, length, power and speed each have their usual units.
How to use it
- Choose Force and lever arm or Power and speed.
- Enter two of the three values, with their units.
- Leave the third empty: it is worked out and highlighted.
- Change the unit of the torque to N·m, lbf·ft or kgf·m to match a manual or spec sheet.
Limits and your data
- τ = F × r assumes you push at right angles to the lever. At another angle only the part of the force at right angles counts: multiply the force by the sine of the angle first.
- Engine torque and power figures are usually peak values at different rpm. Using peak power and peak torque together does not give one engine speed.
- The power formula gives the power at the shaft. Losses in a gearbox, chain or belt mean less arrives at the wheels.
- A torque wrench reading depends on where you hold it; extensions and adapters that lengthen it change the torque applied.
- The calculation runs entirely in your browser; nothing is sent or saved.
Questions
How do I calculate torque from force and distance?
Multiply the force by the distance from the axis. 200 N on a 30 cm wrench is 60 N·m — the example the page opens with.
How do I convert torque to horsepower?
Choose Power and speed, enter the torque and the rpm, and choose hp for the power. 300 N·m at 4,000 rpm is about 125.7 kW, or 168.5 hp.
How hard do I push to tighten a wheel nut to 100 N·m?
On a 45 cm wrench, about 222 N — roughly the weight of 22.7 kg. A longer wrench needs less force for the same torque.
How do I convert N·m to lbf·ft?
Divide by 1.3558. Enter the torque in one unit and switch the field’s unit to the other; the value converts exactly.