# NEMA 17 vs NEMA 23: torque, drivers and real cost > Compare NEMA 17 and NEMA 23 steppers on torque, current, drivers, voltage and Indian prices, and how to size an axis for a robot. Canonical: https://roboticsengineering.in/nema-17-vs-nema-23-stepper/ | Published: 2026-10-28 | Updated: 2026-10-28 | Author: Jignesh Panchal **NEMA 17 and NEMA 23 are mounting standards, not torque ratings.** That one sentence explains most of the confusion around stepper selection. This guide compares the two frame sizes on torque, current, driver, voltage and cost in India, then shows how to choose for a robot axis rather than for a 3D printer. ## What the numbers actually mean | Spec | NEMA 17 | NEMA 23 | | --- | --- | --- | | Frame size | 42 x 42 mm | 57 x 57 mm | | Typical holding torque | 0.3–0.65 N·m | 1.2–3.0 N·m | | Current per phase | 1.5–2.0 A | 2.8–4.2 A | | Shaft | 5 mm | 6.35 or 8 mm | | Typical supply | 12–24 V | 24–48 V | | Driver | A4988, DRV8825, TMC2209 | TB6600, DM542 or similar | | Weight | ~280–400 g | ~700 g–1.2 kg | Two NEMA 17 motors from different manufacturers can differ by 2x in torque. Always read the datasheet for holding torque, rated current and inductance, not the frame size. ## Torque falls with speed A stepper’s holding torque is measured at standstill. As speed rises, torque falls because the coil current cannot rise fast enough through the winding inductance. Higher supply voltage and a chopper driver push that curve out to higher speeds. - NEMA 17 on 12 V: fine for slow axes, weak above a few hundred RPM. - NEMA 17 on 24 V: noticeably better mid-range torque. - NEMA 23 on 48 V: keeps torque at speeds a NEMA 17 cannot reach. - Low inductance motors hold torque higher up the speed range. - Microstepping improves smoothness, not torque. ## Driver and power supply choices | Driver | Motor | Max current | Indicative price in India | | --- | --- | --- | --- | | A4988 | NEMA 17 | ~2 A with heatsink | ₹150–₹350 | | DRV8825 | NEMA 17 | ~2.5 A with cooling | ₹200–₹450 | | TMC2209 | NEMA 17 | ~2 A RMS | ₹450–₹900 | | TB6600 | NEMA 23 | ~4 A | ₹700–₹1,400 | | DM542 | NEMA 23 | ~4.2 A | ₹2,000–₹3,500 | The driver must be rated above the motor current with margin, and the supply must deliver that current without sagging. A 24 V 2 A adapter running two NEMA 23 motors will brown out the moment both accelerate. ## Cost of a complete axis in India | Item | NEMA 17 axis | NEMA 23 axis | | --- | --- | --- | | Motor | ₹600–₹1,500 | ₹1,500–₹3,500 | | Driver | ₹200–₹900 | ₹700–₹3,500 | | Power supply | ₹500–₹1,200 | ₹1,200–₹3,000 | | Pulley, belt, mounts | ₹400–₹1,200 | ₹800–₹2,500 | | Approximate total | ₹1,700–₹4,800 | ₹4,200–₹12,500 | Prices vary with brand and supplier. The point is the ratio: a NEMA 23 axis typically costs two to three times a NEMA 17 axis once driver and supply are included. ## Choosing for a robot, not a printer - **Small arm joints:** NEMA 17 with a planetary gearbox, usually 10:1 to 50:1. - **Shoulder or heavy joint:** NEMA 23 with a gearbox, or a servo if you need closed-loop control. - **Wheel drive:** NEMA 17 geared for a small indoor robot, NEMA 23 geared for a heavier platform. - **Linear axis:** NEMA 23 on a ballscrew or belt for anything carrying real load. - **Pan-tilt:** NEMA 17 direct drive is plenty. - **High-speed spindle feed:** steppers lose torque; consider a servo. Steppers are open loop. They assume the load arrived. If the axis can jam, skip or be back-driven, plan for a limit switch, an encoder or a servo instead of adding a bigger motor. ## A sizing shortcut Estimate the torque at the joint, add 50–100% margin for friction and acceleration, then divide by the gearbox ratio to get the motor torque. Check that figure against the motor’s torque at your target speed, not its holding torque. If the number is close, go one frame size up or add reduction. ## Mistakes that show up as missed steps - Choosing by frame size instead of measured torque. - Running a NEMA 23 at 12 V and wondering why it stalls at speed. - Power supply sized to the motor current with no margin for two axes. - No acceleration ramp, so the motor loses sync on every start. - Microstepping to 1/32 and expecting more torque. - Mechanical binding in the axis that no motor current can overcome. Related: [stepper motor with Arduino](https://roboticsengineering.in/stepper-motor-arduino-guide/), [motor selection for robots](https://roboticsengineering.in/motor-selection-for-robots/), [planetary vs spur gearbox](https://roboticsengineering.in/planetary-vs-spur-gearbox-robot/), [servo vs DC vs stepper](https://roboticsengineering.in/servo-vs-dc-motor-vs-stepper/), [robot arm kinematics](https://roboticsengineering.in/robot-arm-kinematics-basics/). **Is NEMA 23 stronger than NEMA 17?** Usually yes, but NEMA only defines the mounting face. A NEMA 23 typically offers 1.2–3 N·m holding torque against 0.3–0.65 N·m for a NEMA 17, but always check the datasheet. **Can I run a NEMA 23 with an A4988 driver?** No. A4988 and DRV8825 modules are limited to about 2–2.5 A and cannot supply a NEMA 23. Use a TB6600, DM542 or similar external driver. **What power supply do I need for a NEMA 23?** Typically 24–48 V with enough current for all axes plus margin. Undersized supplies cause brownouts and missed steps during acceleration. **Do I need a gearbox with a stepper motor?** For most robot joints, yes. A planetary gearbox multiplies torque and lowers speed, which also keeps the motor in its efficient range. **Why does my stepper lose steps at higher speed?** Torque falls as speed rises because coil current cannot build fast enough. Higher supply voltage, a chopper driver and lower inductance motors all help. Both frames lose steps for the same reasons, and the [lost-step diagnosis order](https://roboticsengineering.in/stepper-motor-missing-steps-fix/) applies whether you choose NEMA 17 or NEMA 23. Balancers usually stay on NEMA 17 frames; the [self-balancing robot build guide](https://roboticsengineering.in/mpu6050-balancing-robot-arduino/) explains the torque margin you need. The motor frame decides the current, and the [stepper driver guide](https://roboticsengineering.in/tmc2209-vs-a4988-stepper-driver/) explains which module can deliver it safely. Frame size does not tell you what the motor will pull at speed, so read the [torque curve explanation](https://roboticsengineering.in/stepper-motor-torque-curve-explained/) before comparing the two sizes. ## Sources and further reading - [NEMA](https://www.nema.org/) — motor frame standards and definitions. - [Pololu](https://www.pololu.com/) — stepper driver documentation and current limits. - [Trinamic](https://www.trinamic.com/) — stepper driver and motion control references. - [Oriental Motor](https://www.orientalmotor.com/) — torque-speed curve guidance.