Cubic Feet per Minute to Horsepower Calculator

This calculator estimates engine horsepower based on cubic feet per minute (CFM) of air flow, engine displacement, and RPM. It can be used for engine performance analysis and tuning purposes.

Input Parameters

Calculation Results

Calculation Formula

HP = CFM × (Displacement × RPM) ÷ (Volumetric Efficiency × 231 × 2π)

Where:
HP = Horsepower
CFM = Cubic Feet per Minute of air flow
Displacement = Engine displacement in cubic inches
RPM = Revolutions per minute
Volumetric Efficiency = Percentage of air the engine can inhale compared to its displacement

Estimated Horsepower

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BHP per Cubic Inch

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Cubic Feet per Minute to Horsepower Calculator Calculator Usage Guide

Learn how to use the Cubic Feet per Minute to Horsepower Calculator calculator and its working principles

How to Use This Calculator

  1. Enter the engine's air flow in Cubic Feet per Minute (CFM) - typically obtained from a flow bench test
  2. Input the engine's displacement in cubic inches (CID)
  3. Enter the engine's operating RPM
  4. Set the volumetric efficiency (typically 85-95% for street engines, higher for racing engines)
  5. Click the "Calculate" button to estimate horsepower

Understanding the Results

The calculator provides two key results:

  • Estimated Horsepower (HP) - The calculated horsepower based on the input parameters
  • BHP per Cubic Inch - Brake horsepower per cubic inch of displacement, which helps compare engine efficiency

Important Notes

This calculator uses the SAE J2212 standard for engine performance calculations. The accuracy depends on the accuracy of the input parameters, especially volumetric efficiency which has a significant impact on the results.

The calculated horsepower is an estimate and may differ from actual engine performance due to many other factors like camshaft characteristics, intake and exhaust system restrictions, and friction losses.