Horsepower Calculator
Adjust the inputs below. Results update as you type.
How it works
1 mechanical HP = 550 ft·lb/s = 745.7 W. 1 metric HP (PS) = 735.5 W. 1 boiler HP = 9,810 W (very different!). Electrical HP = Volts × Amps × Efficiency / 746. Motor nameplate HP is output power; input power is higher due to motor efficiency (typically 85–95%). HP is commonly used for engines, motors, and vacuum cleaners; kW is the SI unit.
Input guidance
- Confirm date/time/unit settings before comparing outputs.
- If a task has optional fields, run both with and without them to understand impact.
- Save scenario variants when making practical decisions.
The formula
Horsepower = (torque × RPM) ÷ 5252 with torque in lb-ft. One mechanical horsepower equals 550 foot-pounds per second, or about 746 watts.
Worked example
An engine making 300 lb-ft at 5,000 RPM produces (300 × 5000) ÷ 5252 ≈ 286 horsepower.
More examples to test
- Quick-pass example: run default assumptions for a first estimate.
- Refined example: update one assumption at a time to isolate impact.
How to interpret results
Use outputs as operational estimates and pair them with local constraints, business rules, or provider requirements.
When this can be inaccurate
Utilities can miss local policy details, special-case rules, and environment-specific constraints.
Change history
- July 2026: Quality-reviewed for publication with formula checks and explanatory copy updates.
Site-wide corrections also appear on the corrections log.
Find productivity tools for everyday workflows
General recommendation, not professional advice.
Frequently asked questions
What is horsepower?+
A unit of power measuring how fast work is done. One horsepower is about 746 watts or 550 foot-pounds per second.
How do horsepower and torque relate?+
Torque is rotational force; horsepower combines torque and speed (RPM). The two curves always cross at 5,252 RPM.
Why 5252 in the formula?+
It comes from converting torque and RPM into power units; it is the constant that links lb-ft and RPM to horsepower.
Why are outputs slightly different from another tool?+
Different tools can use different rounding rules, default assumptions, and treatment of edge cases.
How can I improve estimate reliability?+
Use verified inputs from real records and re-run calculations after major assumption changes.