# Engine Horsepower

> Estimate peak engine horsepower based on displacement, RPM, and volumetric efficiency.

Page: https://askcalculators.com/calculator/engine-horsepower-calculator/
Definition: https://askcalculators.com/calculator/engine-horsepower-calculator/definition.json
JSON Schema: https://askcalculators.com/calculator/engine-horsepower-calculator/schema.json
Version: 7.0.0
Maintained by: AskCalculators (software project; not a credentialed reviewer)
Qualified review: pending. Automated checks do not establish professional approval.
Page status: Live
Review status: Pending

## Use
Open the calculator page and enter values. Query-string parameters can restore and bookmark a calculation.
Example: https://askcalculators.com/calculator/engine-horsepower-calculator/?displacement=5&cylinders=8&rpm=6000&efficiency=0.85

## Inputs
- displacement: Displacement (L); type=number; optional; default=5
- cylinders: Cylinders; type=number; optional; default=8
- rpm: Peak RPM; type=number; optional; default=6000
- efficiency: Efficiency (0.7-1.0); type=number; optional; default=0.85

## Outputs
- result: Result; format=text; primary

## Formula
Estimated horsepower is derived from airflow and the selected rule-of-thumb conversion factor.

Rule-of-thumb estimate; actual power depends on volumetric efficiency, fuel, boost, tune, drivetrain loss, and test method.

## Rules
- Empty optional inputs are undefined, not zero.
- Hidden conditional inputs are ignored.
- Do not invent missing required inputs.

Notice: Rule-of-thumb estimate; actual power depends on volumetric efficiency, fuel, boost, tune, drivetrain loss, and test method.