Torque to Horsepower Converter - Calculate HP from Torque and RPM
Free torque to horsepower converter for calculating horsepower from torque and rotational speed (RPM). Our converter supports multiple torque units (N·m, lbf·ft), speed units (rpm, rad/s, Hz), power units (W, kW, MW), and horsepower types (mechanical, metric, electric, air, boiler). Perfect for automotive engineering, mechanical design, and power system calculations.
Last updated: January 24, 2026
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Conversion Formula:
Power (W) = Torque (N·m) × Speed (rad/s)
Horsepower = Power (W) / 745.70 W (mechanical)
Enter torque and speed to calculate power and horsepower. You can also enter power or horsepower to calculate the other values.
Understanding Torque and Horsepower
Definition
τ = F × r
Torque is the rotational equivalent of force - the ability of a force to cause an object to rotate around an axis. It's measured in Newton-meters (N·m) or pound-feet (lbf·ft). In engines, torque represents the twisting force that rotates the crankshaft.
- Measures rotational force
- Critical for acceleration
- Important for towing capacity
Definition
HP = Torque × Speed
Horsepower is a unit of power measuring the rate at which work is done. One mechanical horsepower equals 745.7 watts. It was originally defined by James Watt to compare steam engine efficiency to horses pulling loads.
- Measures power output
- Important for top speed
- Used in engine ratings
Quick Example Result
Converting 150 N·m torque at 1500 RPM to horsepower:
Torque
150 N·m
Speed
1500 RPM
Horsepower
~31.6 hp
How Our Torque to Horsepower Converter Works
Our torque to horsepower converter calculates power and horsepower from torque and rotational speed using the fundamental relationship: Power = Torque × Angular Velocity. The calculator supports multiple units and can work in reverse - calculating torque from horsepower and speed.
Conversion Formula
Power (W) = Torque (N·m) × Speed (rad/s)Horsepower = Power (W) / 745.70 W (mechanical)HP = (Torque (lbf·ft) × RPM) / 5252 (US units)The formula converts torque and rotational speed to power, then to horsepower. For US units, the constant 5252 comes from converting foot-pounds and RPM to horsepower. The calculator handles all unit conversions automatically.
Calculation Steps
Converting torque to horsepower involves these steps:
- Convert torque to N·m: If using lbf·ft, multiply by 1.35582
- Convert speed to rad/s: If using RPM, multiply by 0.10472 (2π/60)
- Calculate power: Multiply torque (N·m) by speed (rad/s) to get power in watts
- Convert to horsepower: Divide power (W) by 745.70 for mechanical horsepower
- Select horsepower type: Choose the appropriate type (mechanical, metric, electric, etc.)
Types of Horsepower
There are several types of horsepower used in different applications:
Horsepower Types:
- • Mechanical Horsepower (hp(I)): 745.7 W - Most common in US automotive applications
- • Metric Horsepower (hp(M)): 735.5 W - Used in Europe and metric countries
- • Electric Horsepower (hp(E)): 746 W - Used for electric motors
- • Air Horsepower (ahp): 944 W - Used in air conditioning and ventilation systems
- • Boiler Horsepower (hp(S)): 9,809.5 W - Used for boiler capacity ratings
Torque vs. Horsepower
Understanding the difference between torque and horsepower is crucial. Torque is the twisting force that causes rotation, while horsepower is the rate at which work is done. High torque is important for acceleration and towing, while high horsepower is important for top speed and sustained performance.
Key Differences:
- • Torque: Immediate twisting force, measured at a specific RPM
- • Horsepower: Power output over time, calculated from torque and speed
- • For acceleration: High torque at low RPM provides better acceleration
- • For top speed: High horsepower at high RPM enables higher top speeds
- • Relationship: HP = (Torque × RPM) / 5252 (for US units)
Practical Applications
Torque to horsepower conversion is essential in many engineering and automotive applications. Engineers need to understand both metrics to design efficient systems, compare engine performance, and select appropriate motors and engines for specific applications.
Common Use Cases:
- • Automotive engineering: Comparing engine performance, calculating power output
- • Electric motors: Selecting motors based on torque and speed requirements
- • Industrial machinery: Sizing motors and drives for manufacturing equipment
- • Pump and compressor design: Calculating power requirements for fluid systems
- • Generator specifications: Determining power output from engine torque
- • Performance tuning: Optimizing engine modifications for power and torque
Sources & References
- Internal Combustion Engine Fundamentals - John B. HeywoodComprehensive reference for engine power and torque calculations
- Electric Motors and Drives - Austin Hughes, Bill DruryReference for electric motor power and torque relationships
- SAE International - Automotive Engineering StandardsIndustry standards for horsepower and torque measurements
Need help with other torque conversions? Check out our Nm to in-lbs converter and force converter.
Get Custom Calculator for Your PlatformTorque to Horsepower Converter Examples
Input:
- Torque: 150 N·m
- Speed: 1500 RPM
- Conversion factor: 2π/60 = 0.10472
Calculation Steps:
- Step 1: Convert RPM to rad/s: 1500 × 0.10472 = 157.08 rad/s
- Step 2: Calculate power: 150 × 157.08 = 23,562 W
- Step 3: Convert to kW: 23,562 / 1000 = 23.56 kW
- Step 4: Convert to HP: 23,562 / 745.70 = 31.6 hp
Result: 150 N·m at 1500 RPM equals 31.6 mechanical horsepower (hp(I))
This calculation uses the standard conversion factor for mechanical horsepower. Different horsepower types (metric, electric, etc.) use slightly different conversion factors.
US Units Example
200 lbf·ft at 3000 RPM
HP = (200 × 3000) / 5252
= 114.3 hp
Lower Torque Example
50 N·m at 3000 RPM
Power = 50 × 314.16 = 15,708 W
= 21.1 hp
Frequently Asked Questions
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