Sizing guide
How to choose a drone powertrain
Choose your four powertrain parts as one system. The propeller sets how much torque the motor needs to produce. The motor draws current, which makes the pack voltage sag. That sag changes the propeller rpm. Solve the parts together to see how they affect each other.
Use this guide to see what each part does and which values you need. Then check the answer you get.
Step one
The four parts, and what each one is
Get the values in the right-hand column from a datasheet or your own measurements. The simulation does not guess them for you.
| Part | What it contributes | Values the simulation reads |
|---|---|---|
| Propeller | Turns shaft power into thrust. Sets the rpm the motor has to hold. | Diameter, pitch, blade count, weight, maximum rpm. The Full model also reads the measured blade: radius, chord and twist at each station, and the section at each station. |
| Motor | Turns bus current into shaft torque, and loses the rest as heat. | Kv, phase-to-phase winding resistance, pole count, no-load current and its test voltage, maximum current or maximum power, stator diameter and length, weight. Per-phase inductance and rotor inertia when the datasheet gives them. |
| Battery | Sets the voltage the whole system runs at, and sags under load. | Series and parallel cell count, capacity, chemistry, weight, and one resistance mode: C rating, pack resistance, or per-cell resistance. |
| ESC | Switches the pack into the motor. Its losses come off the same budget. | Not a catalogue part: resistance in milliohms, drive type, timing, PWM frequency and synchronous rectification are set per rotor group on the simulation. |
Use the phase-to-phase motor resistance from the datasheet. You can also measure it across two motor leads.
Step two
Two propeller models
You can describe a propeller by its size or its blade geometry. Choose between two models based on the details you have. Each result names the model you used.
| Model | What it reads | What it needs |
|---|---|---|
| Fast model | The size printed on the propeller: diameter, pitch, blade count, a chord-ratio family and section camber. | Nothing else. Any propeller works, including one that is not in the database. |
| Full model | The measured blade: station radius, chord and twist, and the section at each station. | A database propeller with geometry, or one built in the propeller creator. |
If your propeller is in the database, the Full model uses its blade geometry and the Fast model uses its label. If it is not, you can still use the Fast model with the values printed on it.
| Family | Chord ratio | When to pick it |
|---|---|---|
| Thin electric | 0.065 × diameter | Efficient fixed-wing and electric sport props |
| Sport | 0.07 × diameter | General electric flying; the default when the family is unknown |
| Slow flyer | 0.10 × diameter | Large, low-rpm props on light airframes |
| Multirotor | 0.11 × diameter | Wide-bladed quad and hexacopter props |
| Custom | Your own ratio | Measure the chord at 75 % radius and divide by the diameter |
You can set section camber in an advanced field. It defaults to 3.2 % and changes the result less than your choice of family does.
Step three
Check the answer against measured data
Read the validation report for the model named in your result. Each report shows the error against measurements, grouped by propeller family and the quantity measured. Check which operating conditions those measurements cover when you read the error figures.
Read the Full model validation report →
The component database is published under CC BY 4.0, with the source of each row shown. Quote a value anywhere you like; the attribution line is Data: ThrustLab component database (thrustlab.com), CC BY 4.0.
Step four
Three ways to run it
| Surface | How | Account |
|---|---|---|
| The app | Fill in the form, run, read the result. | Free account |
| The API and Python SDK | pip install thrustlab, then an API key in THRUSTLAB_API_KEY. | Free account |
| The MCP server | Point an assistant at https://thrustlab.com/mcp and ask it in words. Setup for each client → | None |
Size your powertrain
Real motors, propellers and batteries, solved together, with the error published.