Estimate torque, speed, and power for rotating equipment. Switch unit systems easily. Build accurate drive calculations with dependable engineering steps.
This graph shows how torque changes with RPM for the current power value.
| Case | System | Power | RPM | Torque |
|---|---|---|---|---|
| Motor A | Metric | 15 kW | 1440 | 99.48 Nm |
| Motor B | Metric | 7.5 kW | 960 | 74.61 Nm |
| Drive C | Imperial | 20 HP | 1750 | 60.02 lb-ft |
| Drive D | Imperial | 35 HP | 1200 | 153.18 lb-ft |
Metric: Power (kW) = Torque (Nm) × RPM ÷ 9550
Metric: Torque (Nm) = 9550 × Power (kW) ÷ RPM
Metric: RPM = 9550 × Power (kW) ÷ Torque (Nm)
Imperial: Power (HP) = Torque (lb-ft) × RPM ÷ 5252
Imperial: Torque (lb-ft) = 5252 × Power (HP) ÷ RPM
Imperial: RPM = 5252 × Power (HP) ÷ Torque (lb-ft)
These equations connect rotational speed, twisting force, and output power for shafts, motors, gearboxes, pumps, and rotating machinery.
Select the calculation mode first. Choose whether you want to calculate torque, RPM, or power.
Pick the unit system that matches your engineering data. Use metric for kW and Nm. Use imperial for HP and lb-ft.
Enter the two known values. Leave the unknown value in place. The calculator will overwrite it after submission.
Press Calculate. The result appears below the header and above the form.
Review the graph to see how torque varies with RPM at the calculated or entered power level.
Use the CSV button for spreadsheets and the PDF button for quick reporting.
RPM and torque are core measurements in rotating equipment design. RPM expresses how fast a shaft completes revolutions in one minute. Torque expresses the twisting force available to turn a load. Power connects both values and shows how much work the machine can deliver over time.
Engineers use these relationships in motors, pumps, compressors, fans, conveyors, mixers, turbines, and machine tools. A design may need high speed with low torque, or lower speed with stronger turning force. Gear ratios often change torque and speed while keeping overall power close to the same, minus system losses.
When torque rises at a fixed speed, power demand also rises. When speed rises at constant torque, power rises too. That is why correct unit selection matters. In SI practice, power is often given in kilowatts and torque in newton meters. In U.S. customary practice, horsepower and pound-feet are common.
This calculator helps estimate missing values quickly during sizing, troubleshooting, and comparison work. It can support motor selection, shaft checks, gearbox studies, and mechanical performance reviews. The graph adds another useful view by showing how required torque changes across a speed range for the selected power.
Always confirm final design values with manufacturer data, service factors, efficiency losses, duty cycle assumptions, and safety requirements. Real equipment performance can differ because of friction, temperature, load variation, startup conditions, and control method. Use this tool as a strong engineering estimate, then verify against project specifications.
RPM means revolutions per minute. It shows how many complete turns a shaft makes in one minute and helps describe rotational speed in machines.
Torque is rotational force. It measures how strongly a shaft can twist a load and is commonly expressed in newton meters or pound-feet.
Power depends on both torque and speed. For a rotating machine, increasing torque at the same RPM increases power, and increasing RPM at the same torque also increases power.
Choose metric when your values use kilowatts and newton meters. Choose imperial when your values use horsepower and pound-feet. Match the calculator to your project units.
Yes. Select the RPM mode, enter known power and torque values, and the calculator will compute rotational speed using the matching engineering equation.
For constant power, torque decreases when RPM increases. The graph reflects that inverse relationship, which is common in rotating power calculations.
Yes. It is useful for motors, drives, gearboxes, and other rotating equipment. Final equipment selection should still include efficiency and service factor checks.
No. It uses direct formulas for ideal engineering relationships. Real systems may have losses from friction, heat, slip, and transmission inefficiency.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.