Motor KV Explained
KV is the motor's unloaded RPM per volt. A 1800KV motor spins at roughly 1800 RPM for every volt you feed it — about 40,000 RPM unloaded on a 6S pack (22.2 V nominal). Under a propeller load real RPM is lower, but KV still sets the motor's speed character.
RPM ≈ KV × battery voltage, unloaded. A 2400KV motor on a 4S pack (14.8 V nominal) spins at about 35,500 RPM with no prop; the KV to RPM calculator does the arithmetic and adds prop tip speed.
The "V" is volts, but KV is not kilovolts. It is the motor's velocity constant (engineers write it Kv), and it says nothing about how much voltage the motor can take - that limit is the motor's rated cell count.
KV is not a quality score. Higher KV is not "better" — it is a winding choice. The same stator is wound with fewer turns of thicker wire (high KV) or more turns of thinner wire (low KV). That trade-off means:
- Lower KV — more torque per amp, happier with higher voltage and bigger props.
- Higher KV — more RPM headroom on lower voltage, but more current and heat if you over-prop it.
The voltage pairing rule
For a given prop size, KV × cell count stays roughly constant. If a 5" quad flies right at 4S with 2400KV, the 6S equivalent wants about 1600–1900KV. That is why motors like the iFlight XING2 2306 ship in multiple KV options — one per battery voltage, not "slow and fast versions".
| Build | Cells | Typical KV |
|---|---|---|
| 65 mm tiny whoop | 1S | 19,000–27,000 |
| 75 mm whoop | 1S | 20,000–22,000 |
| 2" micro / 2S whoop | 2S | 11,000–15,500 |
| 2–2.5" cinewhoop | 3–4S | 4,300–7,200 |
| 3–3.5" cinewhoop / toothpick | 4S | 3,450–3,500 |
| 3.5" cinewhoop | 6S | 2,450–2,650 |
| 5" freestyle / racing | 4S | 2,300–2,700 |
| 5" freestyle / racing | 6S | 1,700–1,960 |
| 4" long range | 4S | 2,750–3,000 |
| 7"+ long range | 6S | 1,250–1,300 |
(The ranges come straight from the motors and quads in our database.)
What happens when you get it wrong
Too much KV for your voltage and prop: the motor demands more current than the ESC and battery can deliver, everything sags and cooks. Too little KV: the quad feels flat and never reaches the RPM the prop needs. When in doubt, copy the KV the manufacturer ships on the BNF for your cell count — it is almost always the safe pairing.
Compare motors by size
Every stator size in the database has its own table with KV options, weight and cell rating side by side: 1103 · 1404 · 1507 · 2004 · 2207 · 2306 · 2806 · 2807 · 3115 - or all motors.
FAQ
What does KV mean on a motor?
KV is the motor's velocity constant: how many revolutions per minute it turns for each volt applied, with no load. A 1800KV motor on 22.2 V spins at about 40,000 RPM unloaded; with a propeller on, real RPM is lower.
What does KV stand for?
Kv is the motor velocity constant. The "V" refers to volts, as in RPM per volt. It is not a kilovolt rating and does not tell you the maximum voltage the motor can handle.
Is a higher KV motor better?
No. Higher KV trades torque per amp for speed per volt. The right KV depends on the battery voltage and prop size: a 5" quad wants roughly 2300-2700KV on 4S and 1700-1960KV on 6S. Too high a KV for the voltage overloads the ESC and battery.
How do you calculate RPM from KV?
Multiply KV by the battery voltage: RPM ≈ KV × volts. That is the unloaded figure; under a prop, expect noticeably less. The KV to RPM calculator works it out for any cell count.
What KV do I need for a 5 inch quad?
Around 2300-2700KV on 4S or 1700-1960KV on 6S, with a 2207 or 2306 motor. Those ranges are what the 5" motors and BNFs in our database ship with.