Horsepower Calculator
Compute horsepower from torque + RPM, or estimate crank HP from 1/4-mile ET or trap speed.
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Inputs
Horsepower
$333.21
248.5 kW
From torque × RPM
333.2 hp
From ET (Fox Roger)
281.2 hp
From trap (Huntington)
316.2 hp
In kilowatts
248.5 kW
1 hp = 0.7457 kW
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How it works
Torque method: HP = torque × RPM ÷ 5252. Fox Roger: HP = weight ÷ (ET/5.825)³. Huntington: HP = weight × (trap/234)³.
Frequently asked questions
Where does 5252 come from?
HP = torque × 2π × rpm / 33,000, and 2π/33,000 simplifies to 1/5252 when torque is in lb-ft. Horsepower and torque curves always cross at 5252 rpm.
Are ET/trap estimates crank or wheel HP?
These formulas approximate crank HP for a typical drivetrain. Actual wheel HP is ~10–15% lower.
Does elevation affect this?
Yes — naturally aspirated engines lose ~3% HP per 1,000 ft of altitude. ET-based estimates already reflect the actual run.
Which formula is more accurate?
Trap speed correlates better with true HP than ET because ET is more sensitive to launch and traction.
What about metric horsepower (PS)?
1 PS = 0.9863 HP. Most European brands rate engines in PS.
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