# Propeller diameter vs pitch

> What do the two numbers on a propeller mean, and how do diameter and pitch trade off?

- 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-diameter-vs-pitch/ · JSON: https://xemstudio.com/api/geometry?object=propeller-diameter-vs-pitch · Plain text: https://xemstudio.com/objects/propeller-diameter-vs-pitch/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

- An RC prop size like 10x6 gives diameter first, then pitch in inches per revolution (APC nomenclature). Pitch is the distance the prop would advance in one turn with no slip (FAA Powerplant Handbook, geometric pitch).
- APC compares pitch to gearing: more pitch gives higher top speed but weaker takeoff and climb; less pitch gives better acceleration and low-speed thrust (Model Aviation, APC Q&A).
- For engine/motor load, APC's rule of thumb is that +1 in diameter is roughly equivalent to -1 in pitch, so a 12x6 loads about like an 11x7 (Model Aviation, APC Q&A).
- 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 |
|---|---|---|
| Size format | diameter x pitch (in); pitch in in/rev | APC Nomenclature |
| Geometric pitch | advance per revolution with no slip | FAA Powerplant Handbook |
| Load equivalence rule | +1 in diameter ~ -1 in pitch (12x6 ~ 11x7) | Model Aviation (APC) |
| Reference build | 12 x 6, 2 blades | APC example |

## Where the files are

- APC Propellers: [APC Propeller Nomenclature](https://www.apcprop.com/wp-content/uploads/2023/05/APC-Propeller-Nomenclature.pdf) — 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
- 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

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

Index: https://xemstudio.com/files/hardware/propeller-diameter-vs-pitch/index.json · license: https://xemstudio.com/files/hardware/propeller-diameter-vs-pitch/LICENSE.md

- propeller-diameter-vs-pitch-propeller: [STEP](https://xemstudio.com/files/hardware/propeller-diameter-vs-pitch/propeller-diameter-vs-pitch-propeller.step) · [STL](https://xemstudio.com/files/hardware/propeller-diameter-vs-pitch/propeller-diameter-vs-pitch-propeller.stl) — 12×6 in propeller, 2 blades: each section set at the geometric pitch angle atan(P / 2πr); chord and section illustrative

## Questions

**Is a 12x6 the same load as an 11x7?**

Roughly, per APC's +1 in diameter = -1 in pitch rule of thumb (Model Aviation).

## Fits with

- [Pitch-to-diameter ratio](https://xemstudio.com/objects/pitch-diameter-ratio/)
- [Propeller blade count (2, 3 and 4 blades)](https://xemstudio.com/objects/propeller-blade-count/)
- [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/)