⚙ Torque Calculator
Calculate rotational force (torque) in Newton-metres, foot-pounds, and inch-pounds. Enter force, lever arm length, and angle.
Torque is the rotational equivalent of linear force. When tightening a bolt with a wrench, the torque depends on the force you apply, the length of the wrench (lever arm), and the angle. Maximum torque occurs at 90°. Torque = Force × Distance × sin(angle). Common uses: engine torque specs (N·m), bolt tightening torque, wrench settings, motor output. A car engine producing 400 N·m at 0.3 m crankshaft radius generates about 1333 N of force.
📊 Torque Unit Conversion Reference
| From | To N·m |
|---|---|
| 1 ft·lb | 1.3558 N·m |
| 1 in·lb | 0.1130 N·m |
| 1 kgf·m | 9.8067 N·m |
| 1 ozf·in | 0.00706 N·m |
🔗 Related Calculators
Understanding Torque: The Rotational Force
Torque is the rotational equivalent of linear force — it describes the tendency of a force to rotate an object around an axis. The formula is straightforward: Torque = Force × Distance × sin(θ), where θ is the angle between the force vector and the moment arm. When the force is perpendicular (θ = 90°), sin(θ) = 1 and the formula simplifies to T = F × d.
Real-World Torque Examples
Torque appears everywhere in engineering and daily life. When you use a wrench, the torque you apply equals the force on the handle multiplied by the wrench length — which is why a longer wrench gives you more mechanical advantage. Engine torque determines a vehicle's ability to accelerate and tow loads: a diesel truck producing 900 N·m of torque can tow far more than a sports car producing 400 N·m, even if the sports car has higher horsepower.
Torque vs. Horsepower
Horsepower and torque are related but distinct: HP = (Torque in lb·ft × RPM) / 5,252. At 5,252 RPM, torque in lb·ft numerically equals horsepower. Below 5,252 RPM, torque exceeds HP; above it, HP exceeds torque. Diesel engines peak torque at low RPM (great for towing); petrol sports engines peak at high RPM (great for top speed). Electric motors produce maximum torque at 0 RPM — instant acceleration.
What Is Torque and How Is It Calculated?
Torque is the rotational equivalent of force — it measures how much a force causes an object to rotate around an axis. τ = F × d × sin(θ), where F is the applied force, d is the distance from the pivot point (the moment arm or lever arm), and θ is the angle between the force vector and the lever arm. When force is applied perpendicular to the lever arm (θ = 90°, sin(90°) = 1), the formula simplifies to τ = F × d. Torque is measured in Newton-meters (N·m) in SI units, or pound-feet (lb·ft) in imperial — note that torque is lb·ft, not ft·lb (though both are used, lb·ft is technically more correct). Tightening a bolt with a 0.3 m wrench using 50 N of force applies 15 N·m of torque.
Torque in Engines: What the Numbers Mean
Engine torque ratings describe rotational force at the crankshaft. A car engine producing 300 lb·ft of torque at 3,000 RPM provides strong pulling force at low engine speeds — important for towing and acceleration from rest. Horsepower and torque are related by: HP = Torque (lb·ft) × RPM ÷ 5,252. This is why the torque and horsepower curves always cross at 5,252 RPM. For practical driving, torque determines how quickly a vehicle can accelerate from low speeds and how much it can tow; horsepower determines top speed and sustained power at high RPM. Diesel engines typically produce more torque at lower RPM than gasoline engines of similar displacement — which is why diesel trucks and trains are preferred for heavy hauling.
Torque in Everyday Tools and Fasteners
Torque wrenches are used in automotive and mechanical work to tighten fasteners to precise specifications, preventing both over-tightening (which can strip threads or break bolts) and under-tightening (which can cause loosening under vibration). Common torque specs: spark plugs 15–25 N·m (11–18 lb·ft), lug nuts 80–130 N·m (60–100 lb·ft) depending on vehicle, cylinder head bolts 70–100 N·m for most passenger cars. When a torque spec isn't available, a general rule is to tighten until snug, then turn an additional 1/4 to 1/2 turn (called torque-angle method). Thread lubricant (anti-seize) reduces the torque required to achieve the same clamping force by 25–30% — always check whether a torque spec assumes lubricated or dry threads.
