Enter Propeller Inputs
The page stays in a single-column flow, while the calculator fields use 3 columns on large screens, 2 on smaller screens, and 1 on mobile.
Example Data Table
These sample cases help users understand the type of output the calculator provides.
| Case | Diameter (m) | Pitch (m) | RPM | Speed (m/s) | Power (kW) | Blades | Approx. Thrust (N) | Approx. Efficiency (%) |
|---|---|---|---|---|---|---|---|---|
| Climb setup | 1.70 | 1.20 | 2400 | 28 | 160 | 3 | 2,210 | 38.7 |
| Cruise setup | 1.80 | 1.40 | 2200 | 45 | 180 | 3 | 2,640 | 66.0 |
| High-speed setup | 1.95 | 1.55 | 2100 | 62 | 240 | 4 | 2,980 | 77.0 |
Formula Used
This model combines actuator-disk momentum theory with practical correction factors. It is designed for preliminary engineering comparison rather than certification-grade prediction.
1) Rotational speed in revolutions per second: n = RPM / 60
2) Disk area: A = πD² / 4
3) Advance ratio: J = V / (nD)
4) Pitch speed: Vpitch = nP
5) Slip ratio: s = (Vpitch − V) / Vpitch
6) Torque: Q = P / ω, where ω = 2πn
7) Forward-flight power balance solved numerically:
Pavail = TV + T3/2 / √(2ρA)
8) Thrust coefficient: Ct = T / (ρn²D⁴)
9) Power coefficient: Cp = P / (ρn³D⁵)
10) Propulsive efficiency: η = TV / P = J(Ct/Cp)
Additional factors adjust the ideal momentum result for pitch ratio, blade count, slip level, tip Mach effects, and overspeed behavior. That makes the output more practical for quick design studies.
How to Use This Calculator
- Enter propeller diameter and pitch in meters.
- Provide shaft RPM, flight speed, and air density.
- Enter shaft power in kilowatts and blade count.
- Set drive efficiency to account for transmission losses.
- Press Calculate Performance to see outputs above the form.
- Review thrust, efficiency, coefficients, torque, and graph trends.
- Download the result summary as CSV or PDF when needed.
- Use multiple runs to compare candidate propeller sizes quickly.
Frequently Asked Questions
1) What does advance ratio mean?
Advance ratio compares flight speed to rotational speed and diameter. It helps show whether the propeller is underloaded, overloaded, or operating near a useful design region.
2) Is this suitable for marine propellers?
No. This version is tuned for air propeller estimation. Water propellers need different density, cavitation treatment, wake fractions, and hydrodynamic correction methods.
3) Why can efficiency drop at high RPM?
Higher RPM increases tip speed, compressibility losses, and profile drag. As tip Mach rises, useful thrust can stop improving even when shaft power increases.
4) Is static thrust exact?
No. Static thrust here comes from momentum theory plus correction factors. Real blades, twist, airfoil sections, and test stand data can shift the result noticeably.
5) Why is slip negative?
Negative slip appears when entered flight speed exceeds pitch speed. That usually indicates unrealistic inputs, windmilling behavior, or a propeller outside its intended operating range.
6) Can I size a new propeller with this?
Yes, for early comparison studies. For final sizing, use manufacturer maps, blade element analysis, structural checks, noise limits, and engine matching.
7) What units are expected?
Enter diameter, pitch, and speed in metric units shown beside each field. Keeping consistent units prevents major coefficient and efficiency errors.
8) Why include blade count if momentum theory uses disk area?
Disk area sets ideal flow, but blade count influences solidity, losses, and practical loading. This calculator applies it as a correction, not a full blade model.