# Wheel Horsepower Calculator

URL: https://speedycalculator.com/calculators/everyday-life/wheel-horsepower/
Last updated: 2026-10-25

> The wheel horsepower calculator converts engine (crank) horsepower to the power that reaches the wheels after drivetrain losses for front-, rear- and all-wheel-drive cars, and works back from a dyno reading to crank power.

## Inputs

- Engine (crank) horsepower (hp)
- Drivetrain
- Custom drivetrain loss (%)

## Results

- Wheel horsepower
- Power lost in the drivetrain
- Wheel power in kW

## Formula

```
Wheel hp = engine hp × (1 − drivetrain loss)
Engine hp = wheel hp ÷ (1 − loss)
```

## Explanation

Manufacturers quote power at the crankshaft, but a chassis dynamometer measures it at the wheels. Gearbox, driveshaft, differential and wheel bearings each take a small share, so typical losses are 10–15% for front-wheel drive, 15–18% for rear-wheel drive and 20–25% for all-wheel drive.

### How to use the Wheel Horsepower Calculator

- **Engine (crank) horsepower**
- **Drivetrain**
- **Custom drivetrain loss**
- Every result field is editable: type into **Wheel horsepower** and **Engine (crank) horsepower** plus every other field update to match.

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter the engine horsepower and pick the drivetrain (or enter your own loss). Type a dyno reading into the result to find the crank horsepower.

### Tips

- Use your own measured figures – fuel economy, speed and prices vary a lot with driving style, traffic, load and season.
- Pick the unit in each field's menu (miles or kilometres, mpg or L/100 km); the calculator converts everything for you.
- Fill up to the brim twice and divide the distance by the fuel added to measure real fuel economy.
- For vehicle modifications, treat results as a starting point and confirm with the parts maker or a professional mechanic.

### Common mistakes to avoid

- Mixing US and imperial (UK) gallons – a UK gallon is about 20% bigger.
- Using the advertised fuel economy instead of real-world figures.
- Forgetting tolls, parking and wear and tear when comparing driving with public transport.

### Inputs explained

FieldWhat to enterEngine (crank) horsepowerIn hpDrivetrainChoose one: Front-wheel drive, manual (≈ 12%), Front-wheel drive, automatic (≈ 15%), Rear-wheel drive, manual (≈ 15%), Rear-wheel drive, automatic (≈ 18%) …Custom drivetrain lossIn %

### What each result means

- **Power lost in the drivetrain** = [Engine (crank) horsepower] - [Wheel horsepower]
- **Wheel power in kW** = [Wheel horsepower]×0.74569987158227

### Example values

How the main result changes when **Engine** changes and everything else stays at the example values above:

Engine (crank) horsepower (hp)Wheel horsepower (whp)150128225191300255375319450383600510

## Worked example

Inputs — Engine (crank) horsepower: 300 hp; Drivetrain: Rear-wheel drive, manual (≈ 15%); Custom drivetrain loss: 17 %.

Results — **Wheel horsepower = 255 whp**; Power lost in the drivetrain = 45 hp; Wheel power in kW = 190 kW.

## FAQ

**How much power is lost through the drivetrain?**
Roughly 10–15% for front-wheel drive, 15–18% for rear-wheel drive and 20–25% for all-wheel drive.

**Why do different dynos read differently?**
Dyno type, correction factors, tyre pressure and temperature all affect the reading; compare runs on the same dyno.

**Is the loss a fixed percentage?**
Not exactly – part of it is fixed friction, so the percentage is lower on high-power cars.

**What formula does the Wheel Horsepower Calculator use?**
Wheel hp = engine hp × (1 − drivetrain loss).