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Supercharger Pulley Ratio Calculator

Estimate supercharger drive ratio from crank pulley size and blower pulley size.

Updated April 16, 2026
Free online tool
Planning and research use

Why this page exists

Forced-induction setup changes are easier to compare when pulley sizes are turned into one drive ratio instead of being discussed only as separate diameters. This calculator helps visitors estimate supercharger pulley ratio from crank and blower pulley size using straightforward pulley math.

Interactive tool

Run the estimate

Enter your numbers and read the result first, then use the sections below to understand what affects the outcome.

Calculator

Supercharger pulley ratio calculator

Estimate supercharger drive ratio from crank pulley size and blower pulley size.

Result

2.53:1

Estimated supercharger drive ratio based on crank pulley diameter divided by blower pulley diameter.

Drive ratio2.53:1

Crank pulley used7.85

Blower pulley used3.10

Drive summaryBlower is overdriven relative to crank speed

7.85 divided by 3.10 gives a supercharger drive ratio near 2.53:1.
Blower is overdriven relative to crank speed.
Use the ratio as a setup-planning number only, because real blower speed still depends on engine RPM, belt control, and safe mechanical limits.

This is a simple pulley-ratio estimate only. Actual blower speed also depends on engine RPM, belt behavior, and the mechanical limits of the setup.

Planning note

Last updated April 16, 2026. Use this tool to compare scenarios and plan ahead, then confirm important details with the lender, employer, insurer, contractor, or other qualified provider involved in the final decision.

How it works

What the calculator is doing

Enter crank pulley diameter and blower pulley diameter.

The calculator divides crank pulley diameter by blower pulley diameter.

It shows the resulting drive ratio and a simple overdrive or underdrive summary.

Understanding your result

This is a simple pulley-ratio estimate only. Actual blower speed also depends on engine RPM, belt behavior, and the safe mechanical limits of the setup.

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Examples

Ways people use this tool

Example scenarios help turn a quick estimate into a more useful comparison or planning step.

Compare two pulley combinations quickly

A ratio figure can make it easier to compare how aggressively two pulley combinations drive the blower.

Check whether a pulley change moves toward more drive

The simple summary can make it easier to see whether the blower is being driven harder or softer.

Use it with boost-planning tools

Pulley ratio often works best beside airflow, fueling, and effective-compression planning tools.

FAQ

Common questions

How is supercharger pulley ratio calculated here?

The calculator divides crank pulley diameter by blower pulley diameter to estimate the drive ratio.

Why does the ratio not equal actual blower RPM?

Because actual blower speed also depends on engine RPM. The pulley ratio only shows how the blower is geared relative to crank speed.

Why is this only a setup estimate?

Because belt slip, real measured pulley size, and safe component speed limits can all change what the combination should actually run.

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Keep comparing

Use these related tools to compare nearby scenarios, check a second estimate, or keep narrowing down the right decision.

Auto ToolsUpdated April 15, 2026