Torque Calculator – Rotational Force
Calculate torque
How to Use
- Enter values
- Click calculate
What Is Torque?
Torque is the rotational equivalent of linear force. It measures the tendency of a force to cause an object to rotate about an axis. The formula is τ = F × d × sin(θ), where F is the applied force, d is the distance from the axis of rotation (lever arm), and θ is the angle between the force vector and the lever arm.
Torque is maximized when the force is applied perpendicular to the lever arm (θ = 90°). When you use a wrench to tighten a bolt, you instinctively push at a right angle to the handle to get the most turning effect. A longer wrench provides more torque for the same applied force.
Units of Torque
The SI unit of torque is the Newton-meter (N·m). In imperial systems, foot-pounds (ft·lb) and inch-pounds (in·lb) are common. Although N·m has the same dimensions as the joule (a unit of energy), torque and energy are physically distinct concepts and should not be confused.
Automotive specifications typically list engine torque in N·m or ft·lb. For example, a typical passenger car engine might produce 200 to 400 N·m of peak torque, while a heavy-duty diesel truck engine can exceed 2,000 N·m.
Relationship Between Torque and Power
Power is the rate at which work is done and is related to torque by the equation P = τ × ω, where P is power in watts and ω is the angular velocity in radians per second. In automotive terms, horsepower equals torque (in ft·lb) multiplied by RPM, divided by 5,252.
An engine can produce high torque at low RPM (like a diesel) or high power at high RPM (like a sport motorcycle engine). Gearboxes trade torque for speed: lower gears multiply torque at the wheels for acceleration, while higher gears reduce torque but increase speed.
Frequently Asked Questions
- What is the difference between torque and horsepower?
- Torque measures rotational force at a given instant, while horsepower (or kilowatts) measures the rate of doing work over time. Torque determines how much pulling or twisting force is available, and horsepower determines how quickly that force can be sustained. The two are related by the formula: HP = Torque × RPM / 5,252.
- Why is a torque wrench important?
- A torque wrench ensures that bolts and fasteners are tightened to a specific torque value recommended by the manufacturer. Under-tightening can cause parts to loosen and fail, while over-tightening can strip threads or crack components. Torque wrenches are essential in automotive work, construction, and aerospace assembly.
- How can I increase torque?
- Torque can be increased by applying more force, using a longer lever arm, or ensuring the force is applied at 90° to the lever arm. In mechanical systems, gear reduction increases torque at the expense of speed. A gear ratio of 3:1 triples the output torque while reducing the output speed to one-third.
- What is the relationship between torque and angular momentum?
- Torque is the time rate of change of angular momentum, analogous to how force is the rate of change of linear momentum. Applying a net torque to an object changes its angular velocity. When no external torque acts on a system, angular momentum is conserved, which explains why spinning ice skaters speed up when they pull their arms in.