Horsepower to Torque Calculator
Convert between horsepower (HP), torque (lb-ft), and RPM using the standard SAE J1349 relationship. Enter any two of the three values and the calculator returns the third, plus conversions to kilowatts (kW) and Newton-metres (Nm). Use this for engine tuning comparisons, dyno sheet analysis, or simply understanding how your vehicle's power output relates to its torque at a given RPM.
Select what you want to calculate:
Horsepower and torque formulas (SAE J1349)
HP = (Torque_lbft x RPM) / 5,252
Torque (lb-ft) = (HP x 5,252) / RPM
RPM = (HP x 5,252) / Torque_lbft
kW = HP x 0.7457
Nm = lb-ft x 1.35582
The constant 5,252 derives from: 1 HP = 33,000 ft-lb/min, and power = torque x angular velocity where angular velocity = 2 x pi x RPM / 60. Rearranging: HP = Torque x RPM x 2pi / (60 x 33,000) = Torque x RPM / 5,252.11...
Typical horsepower and torque by vehicle type
- Economy compact car: 100 to 150 HP, 120 to 180 lb-ft torque, peak torque at 1,800 to 3,000 RPM.
- Mid-size sedan: 180 to 250 HP, 170 to 250 lb-ft, peak torque at 2,000 to 4,000 RPM.
- Half-ton pickup truck (V8 gas): 350 to 400 HP, 380 to 430 lb-ft, peak torque at 3,600 to 4,000 RPM.
- Diesel truck: 400 to 500 HP but 800 to 1,000 lb-ft torque at very low RPM (1,600 to 2,000).
- Electric motor: peak torque available from 0 RPM, which is why EVs feel fast off the line despite moderate peak HP ratings.
Horsepower and torque calculator: frequently asked questions
What is the formula for converting horsepower, torque, and RPM?
The fundamental mechanical relationship is: Horsepower = (Torque x RPM) / 5,252. The constant 5,252 comes from the definition of horsepower (33,000 ft-lb per minute) divided by 2 x pi. This formula is the basis for the SAE J1349 standard for engine power measurement, which is the standard used for all US new-vehicle horsepower ratings.
What is SAE J1349?
SAE J1349 is the Society of Automotive Engineers standard for measuring and reporting net engine power output. All new passenger vehicles sold in the US must have their horsepower rated to this standard. Net power is measured with all standard accessories (alternator, power steering, emissions equipment) installed, at a standardised temperature and pressure, making ratings comparable across vehicles.
What is the difference between horsepower and torque?
Torque (lb-ft or Nm) is the rotational force an engine produces. Horsepower is the rate at which that work is done over time: HP = Torque x RPM / 5,252. High torque at low RPM gives strong off-the-line acceleration and towing ability. High horsepower at high RPM gives top speed. At 5,252 RPM, an engine's torque in lb-ft numerically equals its horsepower in HP.
How do I convert horsepower to kilowatts?
1 mechanical horsepower = 0.7457 kilowatts. So kW = HP x 0.7457. This conversion is defined in NIST Special Publication 330. Note that electric motor power ratings typically use kW, while US automotive ratings use HP. To convert lb-ft to Newton metres: 1 lb-ft = 1.35582 Nm.
Why do horsepower and torque curves cross at 5,252 RPM?
Because the conversion formula HP = (Torque x RPM) / 5,252 means that at exactly 5,252 RPM, HP numerically equals torque in lb-ft. This is a mathematical property of the formula, not a physical phenomenon. On an engine dyno sheet, the HP and torque curves will always intersect at 5,252 RPM (for US customary units).
Official sources
- SAE J1349 Engine Power Standard: sae.org/standards J1349.
- NIST Special Publication 330 (SI unit definitions): nist.gov SP 330.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.