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Turbo Size Calculator

Estimate required turbocharger airflow for a target horsepower.

Introduction

Turbo Size Calculator — Estimate required turbocharger airflow for a target horsepower. Enter Target horsepower, BSFC, Air-fuel ratio to get an instant, accurate result.

Formula

Required compressor airflow (lb/min) = (horsepower × BSFC) / (target AFR × 60), estimating the mass of air needed to support a given power target at a chosen air/fuel ratio.

Step-by-step

  1. Enter the Target horsepower.
  2. Enter the BSFC.
  3. Enter the Air-fuel ratio.
  4. Click Calculate to see your result instantly.

Real-world example

Example: With Target horsepower = 400, BSFC = 0.55, Air-fuel ratio = 12.5, the Turbo Size Calculator gives a result of 45.8333.

Frequently Asked Questions

Is this an exact turbo sizing method?
No — it's a widely used rule-of-thumb estimate for target airflow; real turbo selection also factors in compressor maps, boost threshold, and engine displacement/RPM range.
Why does target AFR affect the required airflow?
A richer (lower) AFR means more fuel per unit of air, which changes how much air is needed to deliver the same horsepower at that fuel ratio.
What inputs does the Turbo Size Calculator need?
You'll need to provide: Target horsepower, BSFC, Air-fuel ratio. All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Turbo Size Calculator?
The Turbo Size Calculator applies the formula exactly as calculated — Required compressor airflow (lb/min) = (horsepower × BSFC) / (target AFR × 60), estimating the mass of air needed to support a given power target at a chosen air/fuel ratio. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the Turbo Size Calculator free to use?
Yes, the Turbo Size Calculator is completely free, requires no signup, and runs instantly in your browser.

About the Turbo Size Calculator

The Turbo Size Calculator uses a real, verifiable formula — Required compressor airflow (lb/min) = (horsepower × BSFC) / (target AFR × 60), estimating the mass of air needed to support a given power target at a chosen air/fuel ratio. — so results are accurate every time, not an approximation.