What formula is used to calculate horsepower from torque?

HP = (Torque in lb-ft × RPM) ÷ 5252. The constant 5252 comes from converting RPM and lb-ft units into consistent power units. For metric, kW = (Torque in Nm × RPM) ÷ 9549.

Why does peak power occur at a higher RPM than peak torque?

Power is proportional to both torque and RPM. Even as torque starts to fall off at high RPM, increasing RPM can still push power higher — until the RPM gain no longer offsets the torque loss.

What is the difference between lb-ft and Nm?

1 lb-ft equals 1.35582 Nm. American manufacturers typically use lb-ft; European and most international standards use Newton-meters (Nm).

Can I use peak torque and peak RPM together to find peak power?

Not directly — peak torque and peak power usually occur at different RPM points. To find peak power, use the torque value measured at the RPM where power peaks, not where torque peaks.

How accurate is this calculator?

It uses the exact standard formulas with no rounding until display. Results match dyno software and OEM spec sheets when the correct torque and RPM values are used.

Engine Power From Torque

Name: Engine Power From Torque
Availability: InStock
Author: Nham Vu

Enter torque and RPM to instantly calculate engine power in horsepower and kilowatts.

Engine Parameters

Torque Unit

Torque (lb-ft)

Engine Speed (RPM)

Power Output

Horsepower

— HP

(SAE mechanical horsepower)

Kilowatts

— kW

(SI metric power)

Formula Used

HP = (Torque lb-ft × RPM) / 5252
kW = HP × 0.7457

Common Engine Reference Points

Engine	Torque	RPM	Power
V8 Sports Car	350 lb-ft	5,252 RPM	350 HP
4-cyl Turbo (Euro)	600 Nm	5,500 RPM	464 HP / 346 kW
Heavy Diesel Truck	1,200 Nm	1,800 RPM	303 HP / 226 kW

Click any row to load those values into the calculator.

Summary

Enter torque and RPM to instantly calculate engine power in horsepower and kilowatts.

How it works

User selects torque unit (lb-ft or Nm) and enters torque and RPM.
For lb-ft input: HP = (Torque × RPM) / 5252; kW = HP × 0.7457.
For Nm input: kW = (Torque × RPM) / 9549; HP = kW / 0.7457.
Results update instantly on every keystroke with two decimal precision.

Use cases

Compare engine specs between vehicles using different unit systems.
Verify dyno sheet results by cross-checking torque, RPM, and power figures.
Estimate power output at different RPM points across a torque curve.
Convert manufacturer torque specs to horsepower for performance comparisons.
Quick sanity-check for engine builds and tuning sessions.
Educational use for automotive engineering students.

Frequently Asked Questions

Last updated: 2026-07-22 · Reviewed by Nham Vu