What does KV mean on a brushless motor?

KV is the motor velocity constant — it tells you how many RPM the motor spins per volt applied with no load (No-load RPM = KV x volts). A 2200KV motor on a 3S LiPo gives 2200 x 12.6 = 27,720 RPM at full charge (4.2 V/cell), and 2200 x 11.1 = 24,420 RPM at nominal voltage (3.7 V/cell). The headline No-load RPM uses the full-charge figure; the breakdown also lists RPM at nominal voltage so you can see both. Under load (a propeller or wheels) actual RPM is typically 70-85% of no-load speed.

Not necessarily. Higher KV means more speed but less torque. Low KV motors (below 1000KV) suit large propellers and slow-flying models. High KV (2000+) suits small, fast models. Medium KV (1000-2000) is a good all-rounder. Match the KV to your application.

How do I choose the right KV for my RC plane?

Trainer/glider: 800-1200KV. Sport aerobatics: 1000-1500KV. Racing: 2000-2800KV. Micro drones: 2500-3500KV. The motor should spin the propeller at the recommended RPM range for your prop diameter — typically 5000-8000 RPM for larger props.

What is the load factor?

Under load (turning a prop or wheels), the motor cannot reach its no-load RPM. The load factor is the percentage of no-load RPM achieved under load. Typically 75-85% for a correctly matched prop/motor combo. An overloaded motor runs at 60-70% and wastes energy as heat.

ModelCalcs

Motor KV Calculator — RPM from KV & Voltage

Work out motor RPM from KV rating and battery voltage, or find the right KV for your needs.

Motor KV Rating

RPM per volt, printed on the motor (e.g. 2200KV). Low KV (<1000) = big props/torque; high KV (2000+) = small fast models

Cell Count (S)Number of LiPo/Li-ion cells in series — each adds its per-cell voltage (3S = 3 cells)

Battery TypeBattery chemistry — sets per-cell nominal and full-charge voltage (LiPo 3.7/4.2 V, LiHV 3.8/4.35 V, LiFe 3.3/3.6 V)

Load Factor (%)

75-85% typical under load

How We Calculate This

Multiplies motor KV rating by battery voltage to calculate RPM, then applies a load factor for real-world speed.

Formula

No-load RPM = KV x Full-charge voltage (cells × full-charge V/cell, e.g. 4.2 V for LiPo)
Loaded RPM = No-load RPM x Load factor %
RPM at nominal voltage = KV x Nominal voltage (cells × nominal V/cell, e.g. 3.7 V for LiPo)

The headline No-load RPM uses full-charge voltage (a fresh pack); under sag the pack sits nearer its nominal voltage, so real-world RPM falls between the two figures before the load factor is applied.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify quantities before purchasing materials.