Torque Calculator
Use this torque calculator to find torque from force and lever arm, with an optional angle (T = F × r × sin θ), to find torque from power and RPM, and to convert between N·m, lb·ft, lb·in, kgf·m and oz·in. Torque is the twisting force on a shaft, wrench or bolt, while horsepower is the rate of doing work, which also depends on speed. For horsepower and kW use the horsepower calculator, to turn power into current use the amp calculator, and for voltage, current and resistance see the Ohm's law calculator.
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Torque from force and lever arm
N·m
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lb·ft
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lb·in
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kgf·m
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oz·in
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Torque from power and RPM
N·m
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lb·ft
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lb·in
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kgf·m
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oz·in
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Torque unit converter
N·m
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lb·ft
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lb·in
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kgf·m
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oz·in
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Torque T = F × r × sin θ, where r is the distance from the pivot to where the force acts and θ is the angle between the force and the arm. 90° means the force is perpendicular, which gives the most torque. From power, T = P ÷ (2π × RPM ÷ 60). 1 lb·ft = 1.3558 N·m = 12 lb·in = 192 oz·in, and 1 kgf·m = 9.80665 N·m. These are physics calculations, not fastener specifications, so use the manufacturer's torque value for bolts.
Horsepower Calculator · Amp Calculator · Ohms Law Calculator
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How it works
- What is torque and how do you calculate it?
- Torque is the twisting effect of a force about an axis, found as force × lever arm: T = F × r. A 50 N force at the end of a 0.3 m wrench gives 50 × 0.3 = 15 N·m, which is about 11.1 lb·ft.
- What lever arm length do I use?
- Use the perpendicular distance from the pivot or axis to the point where the force acts, for example from the centre of a bolt to where you grip a wrench. A longer arm gives more torque for the same force. This calculator does not give bolt tightening specs, so follow the manufacturer's torque value for fasteners.
- What is the difference between torque and horsepower?
- Torque is rotational force. Horsepower is the rate of doing work, so it also depends on speed: power = torque × angular speed, or HP = torque (lb·ft) × RPM ÷ 5252. 100 HP at 3,000 RPM corresponds to about 175 lb·ft (237 N·m). See the horsepower calculator for conversions.
- How do I convert N·m to lb·ft?
- Multiply N·m by 0.7376 to get lb·ft, so 100 N·m is 73.756 lb·ft. Other factors: 1 lb·ft = 1.3558 N·m = 12 lb·in, 1 lb·in = 16 oz·in and 1 kgf·m = 9.80665 N·m. Torque in lb·ft has the same dimension as work in ft·lb, but they are different quantities.
- How does the angle change the torque?
- Only the part of the force perpendicular to the arm twists, so T = F × r × sin θ. At 90° you get the full F × r, at 30° you get half, and at 0° or 180° (pushing along the arm) the torque is zero. With 50 N on a 0.3 m arm at 30° the torque is 7.5 N·m.