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Motor winding & Kv calculator

Kv to torque, rewind turns scaling, wye/delta, cogging steps, winding wire math — exact, no guesswork.

Torque constant KtKt = 9.549 / Kv — the same constant as Kv, seen from the torque side10.61 mNm/A
No-load speedKv × V (ideal — real motors sit a little under)19,980 rpm
Torque at 20 AKt × I, before friction and saturation212 mNm
Back-EMF per 1000 rpm1.11 V
Rewind: turns & termination → new Kv
New KvKv × 12/14771 rpm/V
New Ktmore turns → lower Kv → more torque per amp (not per watt)12.38 mNm/A
Stator & wire
Cogging steps per revolutionLCM(slots, poles) — higher = smoother, finer detents84
Electrical revs per mech revpole pairs — what your ESC actually commutates7
AWG 26 diameter2 strands ≈ one AWG 23 equivalent0.405 mm
Phase resistance (copper, 20°C)66.95 mΩ/m × 3 m — I²R: 80.3 W lost here at 20 A200.8 mΩ

The circuit this computes

H-Bridge Motor Driver — fully explained →

The one constant, two ways

Kv and Kt are the same physical constant expressed in different units: Kt = 60 / (2π · Kv) ≈ 9.549 / Kv. Every electrical watt the motor turns into mechanical power flows through that single number — which is why rewinding for half the Kv exactly doubles the torque per amp, and why no winding change can make a motor fundamentally more powerful. Power limits live in the copper fill, the magnets, and the heat path.

Rewind scaling is plain proportionality: Kv_new = Kv_old × N_old / N_new, times √3 if you also switch wye→delta. Cogging steps per revolution are LCM(slots, poles) — a 12N14P motor detents 84 times per turn, which is why it feels smoother than a 12N4P.

Common questions

What does Kv actually mean?

Revolutions per minute the motor wants to spin per volt of back-EMF — and, flipped around, it IS the torque constant: Kt [Nm/A] = 9.549 / Kv. A high-Kv motor isn't 'weaker'; it trades torque-per-amp for speed, exactly like gearing. The same constant, seen from two sides.

Do more turns mean more torque?

More torque per AMP (lower Kv → higher Kt), not more torque per WATT. The winding doesn't change the motor's underlying ability — copper fill does. More turns means thinner wire in the same slot, so resistance rises and the copper losses meet you on the other side. Rewinding chooses your operating point; it doesn't create free torque.

Wye or delta?

Delta termination raises Kv by √3 (≈1.732) over wye with identical windings. Wye gives more torque per amp and gentler current draw — common for e-bikes and gimbals; delta gives more speed from the same pack — common where RPM matters. Some controllers exploit both with wye-delta switching.

Will this tell me a valid winding layout for my slot/pole combo?

No — and honestly so. Winding tables (which teeth get which phase, in which direction) depend on the slot/pole combination's winding factor, and picking them is real design work. This calculator handles the exact arithmetic around a layout you already have; for the layout itself, consult a winding table for your specific slot/pole count.

Design it in the editor — freeLive electrical checks, automatic BOM, KiCad export.