Calculator Inputs
Example Data Table
The sample below uses the torque and RPM method with a correction factor of 1.00.
| Case | Torque (N·m) | Speed (rpm) | Brake Power (kW) | Brake Horsepower (hp) |
|---|---|---|---|---|
| Engine A | 120 | 1800 | 22.619 | 30.329 |
| Engine B | 150 | 2400 | 37.699 | 50.548 |
| Engine C | 180 | 3000 | 56.549 | 75.821 |
| Engine D | 210 | 3600 | 79.168 | 106.142 |
| Engine E | 240 | 4200 | 105.558 | 141.531 |
Formula Used
1) Torque and RPM method
Brake Power (W) = (2 × π × N × T) / 60
Where N is rotational speed in rpm and T is torque in N·m.
2) Force and arm radius method
Torque (N·m) = Force × Radius
Brake Power (W) = (2 × π × N × Torque) / 60
3) BMEP and displacement method
Brake Power (W) = BMEP × Displacement × (rpm / 60) × Stroke Factor
Stroke factor is 0.5 for 4-stroke engines and 1.0 for 2-stroke engines.
4) Optional correction and loss outputs
Corrected Power = Raw Power × Correction Factor
Estimated Indicated Power = Corrected Power / (1 − Loss Fraction)
How to Use This Calculator
- Choose a calculation mode based on the data you already have.
- Enter torque, or force and radius, or BMEP and displacement.
- Select the correct units for every field before calculating.
- Add engine speed in rpm and an optional correction factor.
- Enter mechanical loss if you also want indicated power estimation.
- Click the calculate button to show results above the form.
- Review the chart for power change across the chosen rpm band.
- Use the CSV or PDF buttons to export the result summary.
FAQs
1) What is brake power?
Brake power is the actual usable power measured at the engine output shaft. It already reflects internal mechanical losses, unlike indicated power.
2) Why does rpm affect brake power?
Power depends on both torque and rotational speed. For the same torque, higher rpm increases the rate of work and therefore increases brake power.
3) When should I use force and radius mode?
Use it for dynamometer or brake arm measurements where shaft torque is not entered directly. The calculator first converts force and radius into torque.
4) What does the correction factor do?
It adjusts raw measured output to a corrected value. This helps standardize results when comparing tests performed under different environmental or test conditions.
5) Is brake horsepower different from kilowatts?
They represent the same power in different units. Kilowatts are SI units, while horsepower is common in engines, motors, and dynamometer reports.
6) Why include displacement and engine cycle?
Those inputs allow the calculator to estimate BMEP from torque or compute brake power directly from BMEP, displacement, and rpm.
7) What is mechanical loss in this page?
Mechanical loss is an optional percentage used to estimate indicated power from corrected brake power. It does not change the reported brake power itself.
8) Can I use this for motors and turbines?
Yes. Any rotating machine with shaft torque and speed can use the torque and rpm method, provided your measurements are accurate and unit choices are correct.