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Propeller RPM Calculator

Convert motor RPM into propeller shaft RPM through a gear reduction or direct drive.

Drivetrain

Ratio ≥ 1; e.g. a 2.5:1 gearbox.

Result

Propeller RPM
24,000RPM
reduction 1.00:1

Direct drive means motor shaft and prop shaft turn at the same speed.

Formula

  1. 1.Propeller RPM = Motor RPM / Reduction Ratio
  2. 2.Direct drive: ratio = 1.

Worked example

  1. 1.Inputs: 24,000 motor RPM, 2.5:1 gearbox.
  2. 2.Prop RPM = 24,000 / 2.5 = 9,600.

Assumptions and limits

  • Check the gearbox is a reduction, not an overdrive — the input expects ≥ 1.
  • Real prop RPM under load is lower.

Related tools

Guides and concepts

FAQ

Where do I find the reduction ratio?

The gearbox spec plate or manual — count gear teeth if undocumented.

Assumptions

  • Reduction ratio is ≥ 1 (motor turns faster than the prop).
  • No slip or drivetrain loss modeled.