Horsepower (HP) is a unit of power measuring the rate at which work is done. One mechanical horsepower equals 550 foot-pounds per second, or 745.7 watts. The unit was coined by James Watt in the late 18th century to compare steam engine output to the work capacity of a horse. Today it is used to describe engine output in cars, motorcycles, boats, and machinery.

How do you calculate horsepower from torque and RPM?

HP = (Torque in lb-ft × RPM) / 5,252. The constant 5,252 comes from 33,000 ft-lbf/min (one horsepower) divided by 2π. Example: an engine producing 300 lb-ft of torque at 4,000 RPM makes 300 × 4,000 / 5,252 = 228.5 HP. Note that at exactly 5,252 RPM, HP always equals torque in lb-ft — this is why torque and HP curves always cross at 5,252 RPM on a dyno chart.

What is the difference between horsepower and torque?

Torque is a rotational force measured in lb-ft or Nm — it determines how hard an engine can push or pull at any given moment. Horsepower is the rate of work — it accounts for both torque and how fast it's being applied (RPM). Low-RPM diesel engines make high torque but moderate HP; high-revving sports cars make high HP with moderate torque because of their very high RPM. HP = Torque × RPM / 5,252.

How do you calculate horsepower from a quarter mile?

Two methods: (1) Elapsed Time (ET) method: HP = Weight × (Speed/234)³, where speed is the trap speed in mph. (2) Original ET formula by Roger Huntington: HP ≈ (Weight / ET³) × K, where K is a constant. More commonly used is the trap speed formula: HP = W × (V/234)³. Example: a 3,000 lb car with a 120 mph trap speed: HP = 3,000 × (120/234)³ = 3,000 × 0.1355 = 406 HP.

What is PS or CV horsepower?

PS (Pferdestärke in German) or CV (Cheval-Vapeur in French) is metric horsepower. 1 PS = 735.5 watts = 0.9863 mechanical HP. It is very close to but slightly less than US mechanical horsepower (1 HP = 745.7 W). European car specs often list output in PS or kW. A car rated at 200 PS makes 197.3 mechanical HP or 147.1 kW.

What is a good horsepower for a car?

Average new cars (2024): 150–200 HP. Sporty compact: 200–300 HP. Performance cars: 300–500 HP. Supercars: 500–1,000+ HP. Economy cars and hybrids: 80–150 HP. Trucks and SUVs: 200–400 HP. A more meaningful metric is power-to-weight ratio: a 3,000 lb car with 300 HP (10 lb/HP) is much quicker than a 5,000 lb SUV with 400 HP (12.5 lb/HP).

How does RPM affect horsepower?

Since HP = Torque × RPM / 5,252, higher RPM directly increases HP even if torque stays constant. This is why high-revving engines (like Honda's S2000 at 8,300 RPM redline) produce high HP despite moderate torque. A diesel engine making 400 lb-ft at 2,000 RPM produces 152 HP; the same torque at 5,000 RPM would produce 381 HP. Sports cars maximize HP by engineering engines to maintain torque at high RPM.

What is power-to-weight ratio and why does it matter?

Power-to-weight ratio (HP per lb, or lb/HP) determines a vehicle's acceleration performance. Lower lb/HP = quicker acceleration. A Bugatti Chiron at ~4.4 lb/HP is dramatically quicker than a family sedan at ~18 lb/HP, even though both are 4-wheel vehicles. Formula: lb/HP = Vehicle weight (lbs) / Horsepower. HP/ton (metric) = Horsepower × 2,204.6 / Weight in kg — used widely in European performance comparisons.

Torque · RPM · Quarter-Mile · kW

Horsepower
Calculator

Q: What is the difference between HP and kW?

Horsepower (HP) and kilowatts (kW) both measure power. 1 mechanical HP = 745.7 watts = 0.7457 kW. To convert HP to kW, multiply by 0.7457. To convert kW to HP, multiply by 1.3410. European car manufacturers typically rate engines in kW (and sometimes PS/CV), while US and UK markets use HP.

Q: What is gross vs net horsepower?

Gross horsepower is measured on a bare engine on a dyno with no accessories (no alternator, no air cleaner, no exhaust restrictions). Net horsepower is measured with all accessories installed, reflecting real-world output. Before 1972, US manufacturers quoted gross HP, which could be 20–40% higher than net HP. Since 1972, SAE net HP is the standard. A 1970 muscle car rated at 360 gross HP might be only ~290 net HP by modern standards.

Calculate engine horsepower from torque and RPM, estimate HP from quarter-mile times, and convert between HP, kW, PS, and watts.

Methods

5,252

HP Constant

HP↔kW

Converter

P/W

Ratio

🏎️

Horsepower Calculator

Torque · Quarter-Mile · Converter

HP = W × (V / 234)³ (Trap Speed method)

Enter vehicle weight + elapsed time (ET) at the finish of a quarter-mile (1/4 mile = 402 m). Use maximum engine effort start-to-finish.

Vehicle Weight include driver + passengers

Quarter-Mile Elapsed Time

sec

HP = W × (V / 234)³

Enter vehicle weight + speed at the quarter-mile finish line (trap speed). The trap speed is the most accurate HP estimator of the two methods.

Vehicle Weight include driver + passengers

Trap Speed (at 1/4 mile finish)

Enter Power Value

From Unit

HP Reference

Horsepower of Famous Vehicles

From economy cars to hypercars — HP, torque, and 0–60 mph times.

Vehicle	HP	Torque (lb-ft)	kW	0–60 mph
Toyota Corolla (2024)	169 HP	151 lb-ft	126 kW	~8.2 sec
Honda Civic Si (2024)	200 HP	192 lb-ft	149 kW	~6.5 sec
Ford Mustang GT (2024)	480 HP	418 lb-ft	358 kW	~4.2 sec
Chevrolet Camaro SS	455 HP	455 lb-ft	339 kW	~4.0 sec
Tesla Model 3 Performance	510 HP	471 lb-ft	380 kW	~3.1 sec
Dodge Challenger SRT Hellcat	717 HP	656 lb-ft	535 kW	~3.6 sec
Lamborghini Huracán	631 HP	443 lb-ft	470 kW	~3.2 sec
Ferrari SF90 Stradale	986 HP	590 lb-ft	735 kW	~2.5 sec
Bugatti Chiron Super Sport	1,578 HP	1,180 lb-ft	1,176 kW	~2.3 sec
Rimac Nevera (EV)	1,914 HP	1,740 lb-ft	1,427 kW	~1.85 sec

🏎️

Torque and HP Curves Always Cross at Exactly 5,252 RPM

This is a mathematical certainty from HP = (Torque × RPM) / 5,252. At 5,252 RPM, the formula simplifies to HP = Torque. This is why every dyno chart in existence shows the torque and horsepower lines intersecting at exactly 5,252 RPM — it's not a coincidence, it's pure algebra. Below 5,252 RPM, torque is higher; above 5,252 RPM, HP is higher.

⚙️

Torque vs Horsepower

Torque is the rotational force the engine exerts — measured in lb-ft or Nm. It determines how hard the engine pushes at any instant. High torque = strong pull from low RPM (diesels, trucks).

Horsepower = Torque × RPM / 5,252. It accounts for how fast you're applying that torque. A sports car with 300 lb-ft at 7,000 RPM makes 400 HP; a diesel truck with 400 lb-ft at 2,000 RPM makes only 152 HP. HP determines top speed and sustained power; torque determines pull and towing capacity.

⚖️

Power-to-Weight Ratio

Raw HP means little without knowing the vehicle's weight. A 300 HP sports car weighing 2,800 lbs (9.3 lbs/HP) accelerates far faster than a 400 HP SUV at 5,200 lbs (13 lbs/HP).

Formula: lbs per HP = Vehicle weight / HP. Lower = faster. Reference: Formula 1 ~1–2 lbs/HP; supercars ~5–7 lbs/HP; performance cars ~8–12 lbs/HP; average sedans ~16–20 lbs/HP; heavy trucks ~25–40 lbs/HP.

How to Calculate Horsepower — All Methods

Horsepower can be calculated multiple ways depending on what data you have available — from a dynamometer (dyno) reading of torque and RPM, from a quarter-mile timing slip, or directly from power measurements in watts or kilowatts.

Method 1: From Torque and RPM (Dyno)

HP = (Torque in lb-ft × RPM) / 5,252 Why 5,252? One HP = 33,000 ft-lbf/min. Converting RPM to radians: 5,252 = 33,000 / (2π) ≈ 5,252.11 Rearranged: Torque = (HP × 5,252) / RPM RPM = (HP × 5,252) / Torque Example: 350 lb-ft @ 4,500 RPM HP = (350 × 4,500) / 5,252 = 1,575,000 / 5,252 = 299.9 HP ≈ 300 HP For metric torque (Nm): HP = (Torque in Nm × RPM) / 7,127 kW = (Torque in Nm × RPM) / 9,549

Method 2: Trap Speed (Quarter-Mile)

HP = W × (V / 234)³ W = vehicle weight in lbs (with driver) V = trap speed in mph at 1/4-mile finish Example: 3,200 lbs car, 105 mph trap speed HP = 3,200 × (105 / 234)³ HP = 3,200 × (0.4487)³ HP = 3,200 × 0.09044 HP = 289 HP (at the wheels) Note: This estimates wheel HP. Add 15% for FWD (drivetrain loss) or 20% for AWD to estimate flywheel (engine) HP.

Method 3: Elapsed Time (ET)

HP = W / (ET / 5.825)³ [Huntington/Sant formula] W = weight in lbs; ET = elapsed time in seconds Example: 3,200 lbs, 13.5 second ET HP = 3,200 / (13.5 / 5.825)³ HP = 3,200 / (2.3176)³ HP = 3,200 / 12.45 HP ≈ 257 HP (at the wheels)

Power Unit Conversions

1 Mechanical HP = 745.7 W = 0.7457 kW = 1.0139 PS 1 Metric HP (PS) = 735.5 W = 0.7355 kW = 0.9863 HP 1 kW = 1,000 W = 1.3410 HP = 1.3596 PS 1 ft-lb/s = 1.3182 × 10⁻³ HP = 1 / 550 HP Quick conversions: 200 HP = 149.1 kW = 202.8 PS 300 HP = 223.7 kW = 304.1 PS 500 HP = 372.8 kW = 506.9 PS

Frequently Asked Questions

Horsepower (HP) is a unit of power measuring the rate of work. One mechanical HP = 550 ft-lbs/sec = 745.7 watts. Coined by James Watt in the 1780s to compare steam engine output to horses. Today it describes engine output in cars, motorcycles, and machinery. One HP was originally the power of a horse lifting 33,000 lbs one foot per minute — or 550 lbs one foot per second.

HP = (Torque in lb-ft × RPM) / 5,252. Example: 300 lb-ft at 4,000 RPM → HP = (300 × 4,000) / 5,252 = 228.5 HP. The constant 5,252 = 33,000 / (2π). Rearranged: Torque = (HP × 5,252) / RPM; RPM = (HP × 5,252) / Torque. Use Panel 1 above to solve for any of the three values.

Torque = rotational force at any instant (lb-ft or Nm). Horsepower = torque × RPM / 5,252 — it accounts for how fast you're applying torque. High torque at low RPM = strong low-end pull (diesels, trucks). High HP at high RPM = sustained top-speed power (sports cars). Both matter: torque for acceleration from rest and towing; HP for sustained high-speed performance.

Trap Speed method: HP = W × (V/234)³. W = weight in lbs (with driver), V = trap speed in mph. Example: 3,200 lb car, 105 mph trap: HP = 3,200 × (105/234)³ = 289 HP at wheels. ET method: HP = W / (ET/5.825)³. These estimate wheel HP — add ~15–20% for engine (flywheel) HP due to drivetrain losses. Use Panels 2 and 3 for instant calculations.

1 mechanical HP = 745.7 watts = 0.7457 kW. To convert HP to kW: multiply by 0.7457. To convert kW to HP: multiply by 1.3410. European cars are typically rated in kW (and sometimes PS). A 150 kW engine = 201 HP. A 300 HP V8 = 223.7 kW. Use our Power Converter tab to convert between HP, kW, PS, and watts.

PS (Pferdestärke / German) or CV (Cheval-Vapeur / French) is metric horsepower. 1 PS = 735.5 W = 0.9863 mechanical HP. It's very close to US HP — 200 PS ≈ 197 HP. European spec sheets often list output in PS or kW. Older European cars have PS ratings; modern EU specs use kW. 1 kW = 1.3596 PS = 1.3410 HP.

Gross HP: measured on a bare engine without accessories (no alternator, no air filter, open exhaust) — inflated figures. Net HP: measured with all production accessories installed, reflecting real-world output. Before 1972, US manufacturers quoted gross HP (20–40% higher). Since 1972, SAE net HP is the standard. A 1970 muscle car quoted at 360 gross HP might be only ~280–290 net HP.

Average new car: 150–200 HP. Sporty compact: 200–300 HP. Performance car: 300–500 HP. Supercar: 500–1,000+ HP. Economy/hybrid: 80–150 HP. But HP alone doesn't tell the full story — power-to-weight ratio matters more. A 300 HP sports car at 2,800 lbs (9.3 lbs/HP) is much quicker than a 400 HP SUV at 5,400 lbs (13.5 lbs/HP).

Since HP = Torque × RPM / 5,252, higher RPM increases HP even if torque stays constant. A diesel making 400 lb-ft at 2,000 RPM = 152 HP; same torque at 5,000 RPM = 381 HP. High-revving sport engines (Honda S2000: 8,300 RPM redline) achieve high HP with modest torque. This is why naturally aspirated sports cars rev high, while torque-focused engines (turbocharged, diesel) make their HP lower down.

Power-to-weight ratio = HP / vehicle weight. Lower lbs/HP = faster acceleration. Formula 1 car: ~1–2 lbs/HP. Supercar: ~5–7 lbs/HP. Performance car: ~8–12 lbs/HP. Average sedan: ~16–20 lbs/HP. For metric: HP per tonne = HP × 2,204.6 / weight (kg). A 300 HP, 1,400 kg sports car = 471 HP/tonne — far quicker than a 400 HP, 2,500 kg SUV = 352 HP/tonne.

Related Calculators

View All Calculators →

HorsepowerCalculator