Horsepower Calculator
Calculate engine horsepower using elapsed time or trap speed methods
Calculate Horsepower
Uses quarter-mile elapsed time to calculate horsepower
Total weight including vehicle, occupants, and all fluids
Time to complete quarter mile (402.3 meters) from standstill
Horsepower Results
Formula: HP = Weight ÷ (Time ÷ 5.825)³
Power-to-Weight Ratio: 0.0000 HP/lb
Conversions: 1 HP = 745.7 W = 550 ft·lb/s
Safety Warning: Only perform quarter-mile tests on closed courses, drag strips, or professional racing facilities. Never attempt high-speed measurements on public roads.
Example Calculation
2018 Ford Mustang GT
Vehicle Weight: 3,706 lbs (with driver and fuel)
Quarter-Mile Time: 12.3 seconds
Method: Elapsed Time
Formula: HP = 3,706 ÷ (12.3 ÷ 5.825)³
Calculated Results
Mechanical Horsepower: ~460 HP
Metric Horsepower: ~466 PS
Power in Watts: ~343 kW
Power-to-Weight Ratio: 0.124 HP/lb
Horsepower Tips
Include total weight: vehicle + occupants + fuel
Use maximum engine output from standstill
Quarter-mile distance = 402.3 meters
Trap speed is end-line speed, not average
Only test at official racing facilities
Power Conversions
Performance Categories
Economy (0.05-0.08 HP/lb)
Fuel efficient vehicles
Average (0.08-0.12 HP/lb)
Standard passenger cars
Sports (0.12-0.15 HP/lb)
Performance vehicles
Supercar (0.15+ HP/lb)
High-performance machines
Understanding Horsepower
What is Horsepower?
Horsepower (HP) is a unit of measurement for power, originally defined by James Watt in the 18th century. He determined that one horse could do 33,000 foot-pounds of work per minute.
Key Definitions:
- 1 Mechanical HP = 745.7 watts
- 1 Metric HP (PS) = 735.5 watts
- 1 HP = 550 foot-pounds per second
Calculation Methods
Elapsed Time Method:
HP = Weight ÷ (Time ÷ 5.825)³
Trap Speed Method:
HP = Weight × (Speed ÷ 234)³
Both methods use quarter-mile (402.3m) performance data and include the total vehicle weight (car + occupants + fuel).
🔧 Torque
- • Definition: Rotational force
- • Units: lb-ft or Nm
- • Feel: Initial acceleration push
- • Best for: Towing, low-end power
- • Peak: Usually at lower RPM
⚡ Horsepower
- • Definition: Rate of doing work
- • Formula: (Torque × RPM) ÷ 5252
- • Feel: Sustained high-speed performance
- • Best for: Top speed, sustained acceleration
- • Peak: Usually at higher RPM
Remember: Torque gets you moving, horsepower keeps you moving fast. Both are important for different aspects of vehicle performance.
Performance Examples
Ford Mustang GT (2018)
Porsche 911 Carrera
Performance Rule of Thumb
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