RC Propeller Pitch Speed Calculator

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, so the 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)

These are the four options in the dropdown and the figures the calculator applies to each:

A slow flyer or park flyer is not in the list. It sits around 60–70% efficient, so pick 3D aerobatic and treat the answer as slightly pessimistic, or read the theoretical figure and take two thirds of it.

Efficiency and load factor are two different things and it is easy to conflate them. The load factor decides how fast the motor actually turns once a prop is bolted on. The efficiency decides how much of that theoretical pitch speed the airframe converts into real forward speed. A 3D plane is punished twice: its coarse prop and heavy airframe slow the motor down, and its enormous control surfaces and draggy shape throw away most of what is left.

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

Pitch on its own tells you very little. A 5-inch pitch is aggressive on a 5-inch racing prop and gentle on a 14-inch scale prop, so what matters is the pitch-to-diameter ratio (P/D), which is pitch divided by diameter. That is the number this calculator grades your prop on:

For maximum thrust (hovering, slow flight) pick a finer prop such as 10×4.7, which is P/D 0.47.
For maximum speed (racing, fast forward flight) pick a coarser one such as 10×7, which is P/D 0.70.
The motor must be able to handle the load, because higher pitch draws more current and generates more heat.