# Propeller blade count (2, 3 and 4 blades)

> Should I use a 2-, 3- or 4-blade propeller?

- Category: Aircraft design › Propellers
- Kind: Standard part
- Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
- Page: https://xemstudio.com/objects/propeller-blade-count/ · JSON: https://xemstudio.com/api/geometry?object=propeller-blade-count · Plain text: https://xemstudio.com/objects/propeller-blade-count/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files Xem Studio Design License (free to use and sell from, not to redistribute as files: https://xemstudio.com/license/)
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**Exact dimensions.** True size, with no printing tolerance added.

## Notes

- Adding blades lets a smaller-diameter prop absorb the same power. APC's rule: with the same blade shape and pitch, a 3-blade prop equals about 90% of a 2-blade's diameter and a 4-blade about 84% (Model Aviation, APC Q&A).
- This is useful for ground or scale clearance. The FAA notes large power increases drove four- and six-blade propellers on full-size aircraft (FAA Powerplant Handbook).
- The file is a reference example built by Xem Studio from the numbers above. Sizes the sources do not fix are illustrative; scale the example to your own vehicle.

## Sizes

| parameter | value or range | source |
|---|---|---|
| 3-blade equivalent diameter | about 90% of 2-blade | Model Aviation (APC) |
| 4-blade equivalent diameter | about 84% of 2-blade | Model Aviation (APC) |
| Worked example (derived) | 12x6 2-blade -> ~10.8x6 3-blade -> ~10.1x6 4-blade | computed from APC rule |
| Reference build | 10.8 x 6, 3 blades | computed |

## Where the files are

- Model Aviation (AMA), J. Smith with APC Propellers: [Common Questions with APC Propellers (Mar 2021)](https://www.modelaviation.com/node/2115) — web — Publisher's page; dimensions are facts
- FAA: [Aviation Maintenance Technician Handbook - Powerplant, Ch. 7 Propellers](https://www.faa.gov/sites/faa.gov/files/09_amtp_ch7.pdf) — web — Publisher's page; dimensions are facts

## Free STEP/STL (1 parts, Xem Studio Design License, Xem Studio)

Index: https://xemstudio.com/files/hardware/propeller-blade-count/index.json · license: https://xemstudio.com/files/hardware/propeller-blade-count/LICENSE.md

- propeller-blade-count-propeller: [STEP](https://xemstudio.com/files/hardware/propeller-blade-count/propeller-blade-count-propeller.step) · [STL](https://xemstudio.com/files/hardware/propeller-blade-count/propeller-blade-count-propeller.stl) — 10.8×6 in propeller, 3 blades: each section set at the geometric pitch angle atan(P / 2πr); chord and section illustrative

## Questions

**What 3-blade replaces a 12x6?**

About 10.8x6 by APC's 90% rule (Model Aviation).

## Fits with

- [Propeller diameter vs pitch](https://xemstudio.com/objects/propeller-diameter-vs-pitch/)
- [Pitch-to-diameter ratio](https://xemstudio.com/objects/pitch-diameter-ratio/)
- [Propeller helix angle and blade twist](https://xemstudio.com/objects/propeller-helix-angle-blade-twist/)
- [Propeller slip and efficiency](https://xemstudio.com/objects/propeller-slip-efficiency/)
- [APC propeller RPM limits](https://xemstudio.com/objects/apc-propeller-rpm-limits/)
- [Propeller naming suffixes (E, SF, MR, P, W, N, C)](https://xemstudio.com/objects/apc-propeller-naming/)