Torque Calculator
Calculate torque from force and radius, convert between N·m, ft·lb, in·lb, and look up standard bolt torque specifications for mechanical engineering.
Torque Unit Conversion Table
| Unit | ft·lb | in·lb | kgf·m |
|---|---|---|---|
| 1 Newton-meter (N·m) | 0.7376 | 8.851 | 0.1020 |
| 1 Foot-pound (ft·lb) | 1 | 12 | 0.1383 |
| 1 Inch-pound (in·lb) | 0.0833 | 1 | 0.01152 |
| 1 kgf·m | 7.233 | 86.8 | 1 |
Standard Bolt Torque Specifications
| Bolt Size / Grade | Recommended Torque |
|---|---|
| M6 (Grade 8.8) | 9-10 N·m (6.6-7.4 ft·lb) |
| M8 (Grade 8.8) | 22-25 N·m (16-18 ft·lb) |
| M10 (Grade 8.8) | 43-48 N·m (32-35 ft·lb) |
| M12 (Grade 8.8) | 74-83 N·m (55-61 ft·lb) |
| 1/4"-20 SAE Grade 5 | 7.9-9.0 N·m (70-80 in·lb) |
| 3/8"-16 SAE Grade 5 | 28-32 N·m (21-24 ft·lb) |
| 1/2"-13 SAE Grade 5 | 68-76 N·m (50-56 ft·lb) |
Frequently Asked Questions
What is torque and how is it calculated?
Torque (τ) is a rotational force measured as the tendency of a force to rotate an object around an axis. Formula: τ = F × r × sin(θ), where F is the applied force, r is the moment arm (distance from pivot), and θ is the angle between force direction and moment arm. For perpendicular force: τ = F × r. Example: 50 N force applied at 0.3 m = 15 N·m torque.
What is the difference between torque and power?
Torque is a static rotational force. Power is the rate of doing work, combining torque and rotational speed. Power (W) = Torque (N·m) × Angular velocity (rad/s). Or: Power (hp) = Torque (ft·lb) × RPM / 5,252. A diesel engine produces high torque at low RPM; a sports car engine produces the same power with lower torque at much higher RPM.
How do I convert N·m to ft·lb?
1 N·m = 0.7376 ft·lb. To convert N·m to ft·lb, multiply by 0.7376. To convert ft·lb to N·m, multiply by 1.3558. Example: 100 N·m = 73.76 ft·lb. Engine specifications between US (ft·lb) and metric (N·m) can be compared using these conversions.
What torque should I use for wheel lug nuts?
Most passenger vehicles: 80-120 ft·lb (108-163 N·m). Light trucks: 100-150 ft·lb. Performance/sports cars: 85-110 ft·lb. Always check your vehicle owner's manual for the exact specification. Use a calibrated torque wrench and torque in a star pattern (not circular) to ensure even clamping force.
What is mechanical advantage in torque?
Mechanical advantage with torque: using a longer wrench handle requires less force to achieve the same torque. A 0.5 m breaker bar requires half the force of a 0.25 m ratchet to produce the same torque. This is why truck wheel nuts require cheater bars — the longer handle provides mechanical advantage. MA = output torque / input torque.