Quick answer
Torque T = P × 60 ÷ (2π × rpm) and power P = T × 2π × rpm ÷ 60. 150 kW at 5,000 rpm corresponds to 286.48 N·m (211.3 lbf·ft), or 201.15 hp.
Choose the direction, then enter power or torque and engine speed. The calculator returns the other quantity.
Related tools: Torque Calculator: Torque from force, lever arm and angle. Engine Displacement Calculator: Displacement from bore, stroke and number of cylinders.
How to use the Engine Torque Calculator
- Choose calculate: Power → torque and Torque → power.
- Optionally, enter power (kW) (above 0).
- Optionally, enter torque (N·m) (above 0).
- Enter engine speed (rpm) (above 0).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Calculate | Choose one: Power → torque; Torque → power | Starts at Power → torque |
| Power (optional) | A number, in kW | > 0 |
| Torque (optional) | A number, in N·m | > 0 |
| Engine speed | A number, in rpm | > 0 |
Formula and method
Formula
T = P × 60 ÷ (2π × rpm); P = T × 2π × rpm ÷ 60
IEEE-754 double precision; shown to the decimals indicated.
1 hp (mechanical) = 745.69987 W; 1 lbf·ft = 1.3558179 N·m.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Calculate = Power → torque; Power = 150; Engine speed = 5000.
| Result | Value |
|---|---|
| Torque | 286.48 N·m |
| In lbf·ft | 211.3 |
| Power in hp | 201.15 |
Example 2
Inputs: Calculate = Power → torque; Power = 75; Engine speed = 3000.
| Result | Value |
|---|---|
| Torque | 238.73 N·m |
| In lbf·ft | 176.08 |
| Power in hp | 100.58 |
Example 3
Inputs: Calculate = Torque → power; Torque = 350; Engine speed = 4000.
| Result | Value |
|---|---|
| Power | 146.61 kW |
| Power in hp | 196.6 |
| Torque in lbf·ft | 258.15 |
The first line is the headline result (torque). Below it the engine Torque Calculator lists in lbf·ft and power in hp, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
The relationship
Power is torque times angular speed. At 5,000 rpm, the angular speed is 523.6 rad/s, so 150,000 W ÷ 523.6 = 286.5 N·m. Power and torque are equal in US units (hp and lbf·ft) at 5,252 rpm.
An engine curve
These are single-point values. A real engine has a torque curve that peaks at some rpm and power that peaks higher. Quoted figures state the rpm at which each peak occurs.
How the result changes with power
Holding every other input at the first worked example, this table changes only power. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Power | Torque | In lbf·ft | Power in hp |
|---|---|---|---|
| 75 | 143.24 N·m | 105.65 | 100.58 |
| 150 | 286.48 N·m | 211.3 | 201.15 |
| 300 | 572.96 N·m | 422.59 | 402.31 |
| 600 | 1,145.92 N·m | 845.18 | 804.61 |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Power: left empty shows "Enter the power." beside that field and no result.
- Torque: left empty shows "Enter the torque." beside that field and no result.
Choosing between the Engine Torque Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Torque Calculator](/science/torque-calculator/) | lever arm, force and angle between force and lever | Torque |
| [Bolt Torque Calculator](/engineering/bolt-torque-calculator/) | nut factor K, nominal diameter and target preload | Torque |
| [Engine Displacement Calculator](/automotive/engine-displacement-calculator/) | bore, stroke and cylinders | Displacement |
| [Angular Velocity Calculator](/science/angular-velocity-calculator/) | starting from | Angular velocity |
| [Angular Acceleration Calculator](/science/angular-acceleration-calculator/) | initial angular velocity, final angular velocity and time | Angular acceleration |
Background: gravity, rotation and optics
Gravity and rotation calculations use a few core relations: a circular orbit has speed v = √(GM ÷ r), torque equals moment of inertia times angular acceleration (τ = Iα), and a thin lens obeys 1/f = 1/dₒ + 1/dᵢ. The moment of inertia depends on both the shape and the axis of rotation.
Use SI units (metres, kilograms, seconds) and check the sign conventions of the formula before interpreting a negative result.
Assumptions and limitations
- Power and torque are only equal at one rpm for a given engine
Use results as engineering estimates and check them against the governing standards, safety factors and a qualified engineer's judgement before relying on them.
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for power and torque to confirm this.
Frequently asked questions
Why do diesel engines have high torque?
They have long strokes and high boost, giving a strong torque at low rpm.
What is the unit of torque?
Newton-metres or pound-feet.
Is 1 kW equal to 1.34 hp?
Yes, approximately: 1 kW is 1.341 mechanical horsepower, so 1 hp is 0.7457 kW.
What does the Engine Torque Calculator calculate?
Convert between engine power and torque at a given rpm. It returns Torque, In lbf·ft and Power in hp.
What formula does the Engine Torque Calculator use?
T = P × 60 ÷ (2π × rpm); P = T × 2π × rpm ÷ 60. 1 hp (mechanical) = 745.69987 W; 1 lbf·ft = 1.3558179 N·m.
What do I need to enter in the engine Torque Calculator?
You enter Calculate and Engine speed (rpm). Optional: Power (kW) and Torque (N·m).
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Power and torque are only equal at one rpm for a given engine.
What does the “Calculate” option change?
It sets how the engine Torque is worked out. The choices are Power → torque and Torque → power.
What is an example of a engine Torque result?
With calculate Power → torque, power 150 and engine speed 5000, the torque is 286.48 N·m.
Where does the method come from?
The method follows: SI and US customary definitions (NIST SP 811).
Can I rely on this calculator for a decision?
Use results as engineering estimates and check them against the governing standards, safety factors and a qualified engineer's judgement before relying on them. For this calculator in particular: Power and torque are only equal at one rpm for a given engine.
Related calculators
- Torque Calculator — Torque from force, lever arm and angle.
- Engine Displacement Calculator — Displacement from bore, stroke and number of cylinders.
- Angular Velocity Calculator — Angular velocity from rpm, frequency, or an angle and time.
- Angular Acceleration Calculator — Angular acceleration from a change in angular velocity.
- Power-to-Weight Ratio Calculator — Power per unit weight of a vehicle.
Sources
- SI and US customary definitions (NIST SP 811)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.