Drone Motor Torque Calculator

Calculator

Choose a mode, enter your specs, then calculate torque. Hover mode estimates shaft power from thrust physics and losses.

Example data table

These examples are illustrative. Real torque depends on prop design, airflow, and ESC timing.

Formula used

• Angular speed: ω = 2π × RPM / 60
• Torque from power: τ = P_shaft / ω
• Hover induced power (ideal): P_i = T^3/2 / √(2ρA)
• Prop disk area: A = π(D/2)²

Hover and thrust modes apply a loss factor (k) and a prop efficiency (η) to move from ideal induced power to a practical shaft power estimate.

How to use this calculator

1. Select a calculation mode that matches your data.
2. Enter a realistic operating RPM, not the motor’s maximum.
3. For hover mode, enter all-up mass and a safety margin.
4. For thrust mode, enter thrust per motor at that RPM.
5. Set prop diameter and air density to match your environment.
6. Review torque in multiple units, then export CSV or PDF.

Drone motor torque guide

1) What torque tells you

Torque is the twisting force the motor must deliver to spin the propeller at a chosen RPM. Higher torque usually means higher current draw, more heat, and a stronger requirement for the ESC and wiring. It is a practical “load” indicator when tuning a build. Small 5-inch freestyle builds often see 0.05–0.15 N·m near mid‑throttle, while heavy‑lift props can exceed 0.3 N·m.

2) Power and RPM relationship

If you know mechanical power at the shaft, torque follows T = P / ω, where ω = 2π·RPM/60. For example, 200 W at 10,000 RPM corresponds to about 0.191 N·m. This mode is useful when you have bench power data or an estimated efficiency.

3) Hover estimate from weight

In hover, total thrust roughly equals weight. This calculator can estimate the thrust per motor from all‑up mass, motor count, and a safety margin (often 20–40%). Using prop diameter, air density, and RPM, it estimates torque consistent with the required thrust at that speed.

4) Thrust-based sizing

If your prop test table lists thrust at a specific RPM, the thrust mode lets you convert that thrust into an equivalent torque estimate. Matching thrust and RPM is important: using a higher RPM than your data will understate required torque and may overspeed the prop.

5) Prop diameter effect

Torque rises quickly with prop size. A modest increase in diameter can demand much more torque because the blades sweep a larger disk area and move more air. When you upsize props, expect lower maximum RPM, higher torque, and a higher chance of ESC temperature limits.

6) Air density and altitude

Air density drops with altitude and higher temperatures. Lower density reduces thrust at a given RPM, so you may need more RPM and power to hold hover. Enter local density (typical sea level ~1.225 kg/m³) to make torque estimates more realistic for your environment.

7) Interpreting results safely

Compare torque in N·m, N·cm, and oz·in to match your datasheets. If calculated torque implies very high current, reduce prop size, reduce pitch, or choose a motor with a better match. Always validate with real thrust and current measurements before flight. Log temperatures during long hover tests.

FAQs

1) What units does this calculator return?

It outputs torque in N·m, N·cm, and oz·in so you can compare motor datasheets and test reports. Use N·m for engineering calculations and oz·in for some hobby catalogs.

2) Should I use motor KV to calculate torque?

KV helps estimate RPM from voltage, but it does not directly give loaded torque. Use your expected RPM under load, then compute torque from power or thrust data for better accuracy.

3) What safety margin is reasonable for hover sizing?

Many pilots use 20–40% margin to cover wind, maneuvers, and battery sag. For payload or long endurance builds, choose the higher end and verify current draw at your target hover RPM.

4) Why does torque change so much with prop size?

Larger diameter and higher pitch move more air per revolution, which increases aerodynamic drag on the blades. That drag shows up as higher required torque, usually raising current and ESC temperature.

5) How do I pick air density if I do not know it?

Start with 1.225 kg/m³ for sea level. Hot weather or high elevation lowers density, reducing thrust at the same RPM. If you fly above 1,500 m, consider 1.06–1.10 kg/m³ as a rough range.

6) Is the result exact for every prop and motor?

No. Prop geometry, blade count, ESC timing, and frame airflow change real torque. Treat the output as an engineering estimate, then confirm with thrust-stand measurements and flight logs before relying on it.