About Torque Calculator
Torque is the rotational force that makes wheels turn, bolts tighten, turbines spin, and engines accelerate. In mechanical and electrical engineering, torque appears everywhere from the lug wrench in a garage to the drive shaft of a multi-megawatt generator. This calculator provides two complementary ways to find torque: from a linear force applied at a distance from a pivot, and from mechanical power delivered at a rotational speed. A technician applying 100 newtons of force 0.5 meters from a bolt axis generates 50 Nm of torque. An electric motor delivering 1,500 watts at 1,500 RPM produces about 9.55 Nm. Because torque and rotational speed trade off for a given power output, this relationship explains why low-RPM electric vehicles use gear reduction to multiply torque at the wheels and why wind turbines need large rotors to capture enough torque to drive generators. Whether you are selecting a motor, designing a drivetrain, or checking fastener preload, converting between force-distance and power-RPM torque gives you a universal engineering language for rotating systems.
How It Works
The calculator computes torque from force and distance using the lever-arm definition. Separately, it computes torque from power and RPM by rearranging the power-rotation relationship: power equals torque multiplied by angular velocity. This lets you enter either a force-and-distance scenario or a power-and-speed scenario and see both results.
Formula & Calculation Logic
Torque from Force = Force (N) × Distance from Pivot (m). Torque from Power = (Power (W) × 60) ÷ (2 × π × RPM). The first formula comes from the definition of a moment. The second rearranges P = τω, where angular velocity ω is expressed in radians per second; multiplying by 60 and dividing by 2π converts RPM to rad/s.
Step-by-Step Guide
- Step 1: Enter the applied force in newtons and the perpendicular distance from the pivot in meters to calculate torque from force.
- Step 2: Alternatively, enter mechanical power in watts and rotational speed in RPM to calculate torque from power.
- Step 3: Review both output values; the force result is independent of RPM, while the power result depends on rotational speed.
- Step 4: Use the appropriate torque value for your specific design or diagnostic task.
Example Calculations
- Scenario 1: A mechanic applies 200 N of force on a 0.3 m wrench handle, producing 60 Nm of torque on a lug nut.
- Scenario 2: An industrial motor rated at 5,500 W and running at 1,750 RPM delivers approximately 30 Nm of torque.
Common Use Cases
- Sizing motors and gearboxes for conveyors, pumps, and fans
- Calculating fastener tightening torque from tool force and lever length
- Matching engine or motor output to load requirements
- Diagnosing mechanical systems by comparing measured and calculated torque
Pro Tips
- Always use the perpendicular distance from the pivot; angled force reduces effective torque by the sine of the angle.
- For belt and pulley systems, remember that torque changes with pulley radius even when power stays constant.
- Convert to foot-pounds by dividing Nm by 1.356 when working with imperial specifications.
- Check that power units match; use watts with RPM, or kilowatts with rad/s, consistently.
Common Mistakes to Avoid
- Using total lever length instead of the perpendicular moment arm
- Confusing torque with power; high RPM with low torque can equal low RPM with high torque for the same power
- Forgetting to convert RPM to radians per second in manual calculations
- Ignoring friction, efficiency losses, and safety factors in real drivetrains
Why Use This Tool?
- Provides two independent torque calculations in one tool
- Supports both SI and common mechanical units
- Helps select motors, drives, and fasteners accurately
- Clarifies the torque-power-speed relationship