Stepper Motor Torque Calculator

This tool calculates key performance metrics including holding torque, full-step and microstepped step resolution, maximum theoretical speed (based on inductance and drive voltage), and estimates the speed-torque curve shape. It also derives motor impedance, electrical time constant, and effective torque per microstep for drive sizing.

Holding torque is directly proportional to rated current and the motor’s phase winding ampere-turns (NI). It represents the maximum static torque the motor can exert when both phases are energized at rated current—no motion occurring. Higher current increases torque up to saturation limits of the magnetic circuit.

Microstepping divides each full step into smaller angular increments (e.g., 16 microsteps per full step), improving positioning resolution and reducing vibration. However, torque per microstep is sinusoidally reduced—peak torque occurs only at full- and half-step positions; at intermediate microsteps, torque drops to ~92% (for 16x) or lower depending on drive quality and current regulation.

Standard hybrid steppers commonly use 1.8° (200 steps/rev) or 0.9° (400 steps/rev) step angles. Rated currents typically range from 0.5 A to 3.5 A for NEMA 17, and 2 A to 6 A for NEMA 23. Holding torque spans 0.1–0.6 N·m (NEMA 17) and 0.5–2.5 N·m (NEMA 23), depending on stack length and design.

While torque depends on current, supply voltage determines how quickly current can rise through the motor’s inductance (τ = L/R). Higher voltage enables faster step rates before torque collapses due to insufficient current buildup—critical for maintaining torque at higher speeds. The calculator uses V_S to estimate maximum usable slew rate and back-EMF limitations.

Yes—this reflects the inherent speed-torque tradeoff in stepper motors. As speed increases, inductive reactance (X_L = 2πfL) impedes current flow, reducing phase current and thus torque. The calculator models this roll-off using motor inductance (derived from V_S, I_RATED, and τ), helping users identify the usable operating range before open-loop失步 (loss of synchronization).

Yes—it informs critical driver specs: required current rating (≥ motor rated current), minimum supply voltage (to achieve target speed), and microstepping compatibility. It also highlights whether a high-voltage chopper drive is needed to overcome inductance limitations at speed, guiding selection between basic L298N-style and advanced TMC2209/TB6600 drivers.

Holding torque is static—measured at zero speed with both phases energized. Pull-out torque (or dynamic torque) is the maximum torque the motor can deliver *while rotating* at a given speed before stalling. This calculator estimates pull-out behavior via speed-dependent current modeling, but actual pull-out depends heavily on drive type, acceleration profile, and load inertia.

Estimates assume ideal sinusoidal current control, negligible rotor inertia effects, and no resonance or damping losses. Real-world torque may be 10–25% lower due to driver nonlinearity, winding resistance heating, and mechanical compliance. Use results as a first-pass design guide—always validate with empirical testing under actual load conditions.

No—the calculator assumes steady-state rated current and ambient temperature. In practice, continuous operation at rated current causes coil heating, increasing resistance and reducing available torque over time. For sustained loads, derate current by 15–30% or implement thermal monitoring; consider using the calculator’s output as a *peak* (not continuous) torque reference.