WHP to HP Conversion – Wheel Horsepower to Horsepower Calculator by Omni

Use our WHP (Water Horsepower) to HP (Horsepower) calculator to accurately convert using Engine HP = WHP / (1 – Drivetrain Loss Percentage) formula.

WHP to HP Conversion Chart

WHP to HP Calculation Values

To convert Wheel Horsepower (WHP) to Engine Horsepower (HP), the formula used is:

HP = WHP / (1 - DL)

where DL is the drivetrain loss. Common values for drivetrain loss are:

• Front-wheel drive: 10% (0.10)
• Rear-wheel drive: 15% (0.15)
• All-wheel drive: 25% (0.25)

Assuming a rear-wheel drive system with a drivetrain loss of 15% (0.15), the calculations for the specified WHP values are as follows:

• 1 WHP to HP: HP = 1 / (1 – 0.15) = 1 / 0.85 ≈ 1.18 HP
• 600 WHP to HP: HP = 600 / (1 – 0.15) = 600 / 0.85 ≈ 705.88 HP
• 280 WHP to HP: HP = 280 / (1 – 0.15) = 280 / 0.85 ≈ 329.41 HP
• 1000 WHP to HP: HP = 1000 / (1 – 0.15) = 1000 / 0.85 ≈ 1176.47 HP
• 650 WHP to HP: HP = 650 / (1 – 0.15) = 650 / 0.85 ≈ 764.71 HP
• 500 WHP to HP: HP = 500 / (1 – 0.15) = 500 / 0.85 ≈ 588.24 HP

WHP to HP Formula

The formula to convert Wheel Horsepower to Engine Horsepower is:

Engine HP = Wheel HP / (1 - Drivetrain Loss Percentage)

Basic WHP to HP Formula:

HP = WHP / Pump Efficiency

Where:

• HP = Mechanical/Brake Horsepower
• WHP = Water Horsepower
• Pump Efficiency = Decimal value (typically 0.60-0.85)

Water Horsepower Formula:

WHP = (Flow × Head × Specific Gravity) / 3960

Where:

• Flow = Gallons per minute (GPM)
• Head = Total head in feet
• Specific Gravity = Fluid density relative to water (water = 1.0)
• 3960 = Conversion constant

Expanded Calculation:

Total HP = (Flow × Head × SG) / (3960 × Pump Efficiency)

Unit Conversions:

1 HP = 0.746 kW
1 kW = 1.341 HP
Flow (m³/hr) = Flow (GPM) × 0.227
Head (meters) = Head (feet) × 0.3048

For example, using the standard 15% drivetrain loss:

Engine HP = Wheel HP / 0.85

Let’s break this down with a practical example:

Suppose your car produces 300 WHP on a dynamometer. To estimate the engine horsepower:

Engine HP = 300 / 0.85 = 352.94 HP

This calculation suggests that the engine is producing approximately 353 HP at the crankshaft.

How to convert Wheel Horsepower to HP?

To perform the conversion:

• Determine the Wheel Horsepower: This is usually measured on a dynamometer.
• Estimate the drivetrain loss: While 15% is a common average, it can range from 10% to 20% depending on the vehicle.
• Apply the formula: Use the equation mentioned above.

Imagine a sports car measures 400 WHP on a dynamometer. The owner knows it has a highly efficient drivetrain with only 12% loss.

To calculate the Engine HP:

Engine HP = 400 / (1 - 0.12) = 400 / 0.88 = 454.55 HP

In this case, the engine is likely producing about 455 HP at the crankshaft.