RC Propeller Pitch Speed Calculator
Calculate the theoretical pitch speed of an RC aircraft or drone based on propeller pitch, diameter, and motor RPM.
Propeller pitch speed is the theoretical maximum speed an RC aircraft could achieve if the propeller moved through the air with zero slip — like a screw turning through wood. In reality, propellers slip through the air, so actual speed is always lower. Pitch speed is still the most useful metric for comparing propellers and predicting aircraft performance.
Pitch Speed Formula
Pitch Speed (m/s) = RPM × Pitch (inches) × 0.0254 / 60
Or in more practical units:
Pitch Speed (km/h) = RPM × Pitch (inches) × 0.0254 × 60 / 1000
Simplified: Pitch Speed (km/h) = RPM × Pitch × 0.001524
Pitch Speed (mph) = RPM × Pitch × 0.000947
Where:
- RPM = motor speed under load (not the no-load KV × voltage)
- Pitch = the distance the propeller would advance in one revolution (given in inches on the prop label)
Understanding Propeller Notation
A propeller labeled 10×6 means:
- 10 = diameter in inches (the total span of the prop)
- 6 = pitch in inches (the theoretical advance per revolution)
Higher pitch = more speed but more motor load. Lower pitch = more thrust but lower top speed.
Worked Example
A 10×6 propeller on a motor spinning at 12,000 RPM:
Pitch Speed = 12,000 × 6 × 0.001524 = 109.7 km/h (68.2 mph)
With typical propeller efficiency of 70–80%, the actual aircraft speed would be approximately 77–88 km/h.
Propeller Efficiency (Slip)
| Aircraft Type | Typical Efficiency | Slip % |
|---|---|---|
| High-speed racing quad | 75–85% | 15–25% |
| Sport/trainer airplane | 70–80% | 20–30% |
| 3D aerobatic plane | 50–65% | 35–50% |
| Slow flyer / park flyer | 60–70% | 30–40% |
| Scale model (large prop) | 75–85% | 15–25% |
Motor RPM Under Load
The actual RPM under load is lower than KV × Voltage. A rough estimate:
Loaded RPM ≈ Motor KV × Battery Voltage × 0.80
For example, a 1000 KV motor on a 3S LiPo (11.1V): Loaded RPM ≈ 1000 × 11.1 × 0.80 = 8,880 RPM
The 0.80 factor accounts for internal resistance, propeller drag, and voltage sag under load. For more aggressive setups, the factor may drop to 0.70. For lightly loaded motors, it may be as high as 0.85.
Choosing Propeller Pitch
For maximum thrust (hovering, slow flight): use lower pitch (e.g., 10×4.7). For maximum speed (racing, fast forward flight): use higher pitch (e.g., 10×7). The motor must be able to handle the load — higher pitch draws more current and generates more heat.