The Core Equation
Theoretical Unloaded RPM
KV stands for RPM per Volt. It tells you how many times a motor will spin per minute for every 1 volt applied (with no propellers attached).
// RPM PREDICTOR
Max Theoretical RPM
44,100
Target 5" RPM is usually 30k - 40k. Don't exceed 50k on a 5-inch prop unless you like exploding plastic.
Standard Pairings
| Drone Class | Voltage | Common KV | Philosophy |
|---|---|---|---|
| 65mm Whoop | 1S | 19,000 - 30,000 | High KV needed for low voltage. |
| 3-inch Toothpick | 2S-3S | 8,000 - 11,000 | The efficiency sweet spot. |
| 5-inch Freestyle | 4S | 2,300 - 2,700 | Old school standard. High current. |
| 5-inch Freestyle | 6S | 1,600 - 1,950 | Modern pro standard. High efficiency. |
The 6S Revolution
Why did the world move from 4S (high KV) to 6S (low KV)? It's all about Heat and Voltage Sag.
By increasing the voltage (V), we can use less current (I) to get the same total power (P = V * I). Less current means your batteries don't struggle as much, your ESCs stay cooler, and your motors feel more "consistent" throughout the entire flight.
⚠️ PRO TIP
If you are switching from 4S to 6S but only have 4S motors, you can use a "Motor Output Limit" in Betaflight (e.g., 66%) to safely fly without burning them out. However, if you do the reverse and put a 4S battery on 6S motors, the drone will feel extremely underpowered and sluggish.