Calculating your wheel horsepower is straightforward once you know the Drivetrain Loss formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Drivetrain Loss Calculator.
What is Drivetrain Loss?
The Drivetrain Loss calculation tells you your wheel horsepower from a few simple inputs. The figure you are solving for here is the wheel horsepower.
The Drivetrain Loss formula
The core formula is:
Wheel horsepower = Engine (crank) horsepower × (1 - Drivetrain loss ÷ 100)Here is what each input means:
- Engine (crank) horsepower — a value measured in hp. Example: 200 hp.
- Drivetrain loss — a percentage, such as an annual rate. Example: 15%.
How to calculate it step by step
- Write down the engine (crank) horsepower (for example, 200 hp).
- Write down the drivetrain loss (for example, 15%).
- Apply the formula above to get your wheel horsepower.
- Double-check the result with the Drivetrain Loss Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Engine (crank) horsepower | 200 hp |
| Drivetrain loss | 15% |
| Wheel horsepower | 170.0 |
| Power lost | 30.0 |
With engine (crank) horsepower of 200 hp and drivetrain loss of 15%, the wheel horsepower works out to 170.0.
Example 2
With engine (crank) horsepower of 400 hp and drivetrain loss of 15%, the wheel horsepower works out to 340.0.
| Result | Value |
|---|---|
| Wheel horsepower | 340.0 |
| Power lost | 60.0 |
Example 3
With engine (crank) horsepower of 100 hp and drivetrain loss of 15%, the wheel horsepower works out to 85.0.
| Result | Value |
|---|---|
| Wheel horsepower | 85.0 |
| Power lost | 15.0 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
Prefer not to do the maths by hand? — the Drivetrain Loss Calculator does it instantly, for free, with the formula and a worked example built in.
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