Horsepower Calculator
Calculate horsepower from torque and RPM, convert between different power units, and determine engine performance metrics for automotive and mechanical applications.
Calculation Type
Calculate Horsepower from Torque & RPM
Quick Examples
Results
💡 Performance Tips:
- • Higher RPM generally produces more horsepower
- • Torque is more important for acceleration
- • Peak power usually occurs at higher RPM than peak torque
- • Engine efficiency depends on the RPM range
- • Forced induction can increase power density
How to Use the Horsepower Calculator
To calculate horsepower and analyze engine performance:
- Select the calculation type from the dropdown menu
- Enter the required values (torque, RPM, force, velocity, etc.)
- Choose appropriate units for your measurements
- View the calculated horsepower and power conversions
- Analyze engine performance metrics and efficiency ratings
- Use the quick examples to understand typical engine specifications
How Horsepower is Calculated
From Torque and RPM
Formula: HP = (Torque × RPM) ÷ 5,252
Example: (400 lb-ft × 4,000 RPM) ÷ 5,252 = 304.7 HP
From Force and Velocity
Formula: HP = (Force × Velocity) ÷ 550
Example: (1,000 lbf × 60 ft/s) ÷ 550 = 109.1 HP
From Work and Time
Formula: HP = Work ÷ (Time × 550)
Example: 33,000 ft⋅lbf ÷ (60 seconds × 550) = 1.0 HP
Power Unit Conversions
- 1 HP = 0.7457 kW
- 1 HP = 1.0139 PS (metric horsepower)
- 1 HP = 2,544.43 BTU/hr
- 1 HP = 550 ft⋅lbf/s
Example Calculation
Scenario: V8 Engine Performance Analysis
- Peak Torque: 400 lb-ft at 4,000 RPM
- Redline: 6,500 RPM
- Displacement: 5.0 liters
Calculations:
- Peak Horsepower: (400 × 4,000) ÷ 5,252 = 304.7 HP
- HP per Liter: 304.7 ÷ 5.0 = 60.9 HP/L
- Power in kW: 304.7 × 0.7457 = 227.2 kW
Frequently Asked Questions
What's the difference between horsepower and torque?
Torque is rotational force, while horsepower is the rate of doing work. Torque determines acceleration capability, while horsepower determines top speed and sustained power output.
Why do horsepower and torque curves cross at 5,252 RPM?
This is due to the mathematical relationship in the horsepower formula. At 5,252 RPM, the numerical values of horsepower and torque (in lb-ft) are equal.
How accurate are manufacturer horsepower ratings?
Modern ratings are quite accurate as they follow standardized testing procedures (SAE J1349). However, real-world conditions may affect actual power output.