Kv to RPM Calculator

| Added in Physics

What is Kv to RPM and Why Should You Care?

Understanding the Kv to RPM concept unlocks the full potential of your electric motor. The Kv rating translates directly to rotations per minute (RPM) based on the applied voltage. This is essential for optimizing performance in RC cars, drones, and any brushless motor application.

How to Calculate Kv to RPM

The formula is straightforward:

[\text{RPM} = \text{Kv Rating} \times \text{Voltage}]

Where:

  • Kv Rating is the motor's velocity constant (RPM per volt)
  • Voltage is the electrical potential difference in volts

Calculation Example

If you have a motor with a Kv rating of 120 and supply it with 90 volts:

[\text{RPM} = 120 \times 90 = 10,800 \text{ RPM}]

Your motor spins at 10,800 RPM under no-load conditions.

Calculation Steps

  1. Determine the Kv rating: Check your motor specifications
  2. Determine the voltage: Measure or note your power supply voltage
  3. Multiply them together: RPM = Kv Rating × Voltage
  4. Verify with actual testing: Real-world RPM may differ slightly

Quick Reference

Kv Rating 3S (11.1V) 4S (14.8V) 6S (22.2V)
1000 11,100 14,800 22,200
2000 22,200 29,600 44,400
2300 25,530 34,040 51,060
2600 28,860 38,480 57,720

Understanding this relationship helps you select the right motor and battery combination for your project.

Frequently Asked Questions

Kv is the velocity constant of a brushless motor, indicating how many RPM the motor turns per volt applied with no load. A 1000 Kv motor at 10V would spin at approximately 10,000 RPM unloaded.

Yes, higher Kv motors spin faster at the same voltage but typically produce less torque. Lower Kv motors are slower but more powerful for heavy loads.

The calculation gives theoretical no-load RPM. Under actual load conditions, RPM will be lower due to resistance, friction, and efficiency losses.

For drones, 2200-2600 Kv is common for 5-inch props. RC cars often use 3000-5000 Kv. Lower Kv (1000-1500) suits larger propellers and heavier loads.