Complete guide
Horsepower Calculator: formula, worked example and interpretation
Convert rotational torque and speed into mechanical power in horsepower and kilowatts. Enter the known values and the result updates instantly with an auditable breakdown.
What the Horsepower Calculator answers
Convert rotational torque and speed into mechanical power in horsepower and kilowatts.
Use the breakdown to compare the result with the source values before making a decision.
Formula and variables
The calculation uses hp=torque(lb-ft)×rpm/5252; kW=torque(N·m)×rpm/9549. Every variable comes directly from a labeled field.
hp=torque(lb-ft)×rpm/5252; kW=torque(N·m)×rpm/9549Worked example
300 lb-ft at 5,000 rpm is approximately 285.6 mechanical horsepower.
Changing any field recalculates the result immediately, so nearby scenarios can be compared without reloading the page.
How to use the result
Treat the result as a planning value and compare it with the detailed rows shown beside it.
Keep units and time periods consistent. Use the share or PDF action to preserve the exact assumptions.
Assumptions and scope
This is shaft power at the stated torque and speed; drivetrain loss, measurement correction and engine operating conditions are separate.
The calculator exposes its assumptions instead of filling missing facts with hidden estimates.
Accuracy checks
Confirm the units, dates, rates and source figures before relying on the output.
Round only the displayed answer; Calculator24 keeps full JavaScript precision for intermediate arithmetic and exported values.
Input and output checklist
| Item | What to enter or review |
|---|---|
| Inputs | Torque unit, Torque, Rotational speed (rpm) |
| Equation | hp=torque(lb-ft)×rpm/5252; kW=torque(N·m)×rpm/9549 |
| Example | 300 lb-ft at 5,000 rpm is approximately 285.6 mechanical horsepower. |
| Limit | This is shaft power at the stated torque and speed; drivetrain loss, measurement correction and engine operating conditions are separate. |
Frequently asked questions
What does this Horsepower Calculator calculate?
Convert rotational torque and speed into mechanical power in horsepower and kilowatts.
Which formula does it use?
hp=torque(lb-ft)×rpm/5252; kW=torque(N·m)×rpm/9549
Does the result update while I type?
Yes. Valid changes recalculate after a short delay and the previous result is not substituted for invalid input.
Which assumptions should I check?
Check units, rates, dates and every source value shown in the form.
Is the result exact?
This is shaft power at the stated torque and speed; drivetrain loss, measurement correction and engine operating conditions are separate.
Can I save or share the calculation?
Yes. Copy, Share, WhatsApp, PDF/Print, CSV, comparison and parameterized-link actions are available.
What to keep in mind
This is shaft power at the stated torque and speed; drivetrain loss, measurement correction and engine operating conditions are separate.
Results display up to 8 decimal places; exported numbers preserve calculation precision. This is a calculation summary, not an official certificate.