Torque Calculator
Calculate torque from force, lever arm and angle — in newton-meters, pound-feet and kilogram-force meters — and the power that torque delivers at a given rpm.
Twisting force from a push on a lever, and the power it makes when turning.
How the torque calculator works
Torque is force times the perpendicular distance from the pivot: τ = F r sin θ, where θ is the angle between the force and the lever arm. Pushing straight down on a spanner (90°) gives the full F × r; pushing along the handle gives none. Engines quote torque in N·m or lb·ft, and the power they deliver is torque × angular speed: P = τ × 2π × rpm ÷ 60.
A 100 N push on a 0.3 m spanner produces 30 N·m — a typical wheel-nut torque is 110 N·m.
Formula: τ = F r sin θ · P = τ ω = τ × 2π × rpm ÷ 60
Worked examples
| Inputs | Torque | Note |
|---|---|---|
| 100 N on a 0.3 m spanner at 90° | 30 N·m | 30 N·m |
| The same push at 45° | 21.21 N·m | 21.2 N·m — sin 45° |
| 200 N·m engine at 3,000 rpm | 200 N·m | 62.8 kW, 84 hp |
FAQFrequently asked questions
What is the difference between torque and power?
Torque is the twisting force; power is torque times how fast it turns. An engine's power peak is where torque × rpm is highest, usually well above the torque peak.
How do I convert N·m to lb·ft?
Divide by 1.3558. 100 N·m is 73.8 lb·ft.
Why does a longer spanner help?
Torque is force times arm. Doubling the arm doubles the torque for the same push — or halves the push needed.
What torque do wheel nuts need?
Typically 90–140 N·m for passenger cars; check the manual. A torque wrench set to the figure is the only reliable way.
Where these figures come from
- NIST — CODATA 2018 fundamental physical constants — G, g₀, R, c
- NIST Special Publication 811 — Guide for the use of the International System of Units — unit conversions
- The Engineering ToolBox — material properties — specific heats, expansion coefficients, densities
- National Institute of Standards and Technology — the US measurement authority
Last checked: September 2026. Constants are the CODATA 2018 values; formulas are the standard textbook forms.