A practical guide to what the NEMA number on a stepper motor actually means — with a size, torque, and application chart for choosing between NEMA 8 and NEMA 34.
MOTOR ENGINEERING KNOWLEDGE Published September 20, 2026 · 7 min read · By Apexwell Engineering Team
A stepper motor's NEMA number refers to its faceplate size, not its performance — NEMA 17 means a 1.7-inch (about 42 mm) square mounting face, full stop. It says nothing about torque, current, or step angle on its own, which is exactly where a lot of first-time buyers get tripped up when comparing a stepper motor on a datasheet against one in a different manufacturer's catalog.
What does the NEMA number actually mean?
NEMA stands for the National Electrical Manufacturers Association, and the sizing convention it standardized is simple: take the NEMA number, divide by 10, and that's the faceplate width in inches. A NEMA 17 stepper motor — sometimes just called a stepping motor in older catalogs — has a 1.7 in × 1.7 in (43 mm × 43 mm) mounting face. A NEMA 23 is 2.3 in (57 mm), and a NEMA 34 is 3.4 in (86 mm).
What the NEMA number does not tell you is body length, holding torque, shaft diameter, or step angle. Two NEMA 17 motors from two different manufacturers can have a torque difference of 4x or more, because body length (often called stack length) varies independently of faceplate size. A short, single-stack NEMA 17 and a long, double-stack NEMA 17 share the same mounting footprint but can differ enormously in torque and current draw.
NEMA stepper motor size chart
Face width to torque is not a fixed ratio, but the table below gives realistic ranges for each frame size, along with where each size typically ends up in a real design, and which Apexwell model covers that frame:
NEMA size | Face width | Typical holding torque | Common use | Apexwell model |
NEMA 8 | 20 mm | 1 – 3 N·cm | Camera/lens focus, compact instruments | AW20HS |
NEMA 11 | 28 mm | 3 – 8 N·cm | Small 3D printer axes, medical pumps | AW28HS |
NEMA 14 | 35 mm | 8 – 20 N·cm | Desktop 3D printers, lab equipment | AW35HS |
NEMA 16 | 39 mm | 15 – 30 N·cm | Compact linear actuators, gimbals | AW39HS |
NEMA 17 | 42 mm | 13 – 65 N·cm | 3D printers, desktop CNC, robotics joints | AW42HS |
NEMA 23 | 57 mm | 40 – 120 N·cm | CNC mills, laser cutters, mid-size automation | AW57HS |
NEMA 24 | 60 mm | 70 – 150 N·cm | Packaging equipment, conveyors | AW60HS |
NEMA 34 | 86 mm | 150 – 500 N·cm | Industrial machinery, large-format CNC | AW86HS |
How to choose the right NEMA size for your application
● Start from torque, not from size. Calculate the torque your load actually requires at your target speed first, then pick the smallest NEMA frame that clears that number with margin — oversizing wastes cost, weight, and current draw for no benefit.
● Check your existing mounting footprint before assuming a size. If you're replacing a motor rather than designing a new mount, measure the faceplate and bolt pattern directly rather than guessing from the old motor's label, since suffix letters and mounting variants can change the bolt spacing within the same NEMA size.
● Leave headroom for closed loop. If there's any chance you'll upgrade to a closed loop configuration later, confirm the frame size you choose is available with an encoder option — not every stack length within a NEMA size is offered in both open loop and closed loop.
Bigger isn't always better
It's tempting to size up "just in case," but a larger NEMA frame brings real trade-offs: higher motor mass adds inertia the driver has to accelerate and decelerate, a bigger frame usually needs a higher-current driver and heavier cabling, and larger stepper motors generate more heat at a given duty cycle, which can force a design change in enclosure ventilation. In a market where 3D printers, CNC machines, and robotics all compete for the same NEMA 17 and NEMA 23 stepper motor supply, the right-sized motor is usually the cheaper, cooler-running, and easier-to-integrate choice — not the biggest one available.
Where this connects to our own product line
Apexwell manufactures hybrid stepper motors across the full NEMA range referenced above, from the compact AW20HS (NEMA 8) up to the AW86HS (NEMA 34), including the AW28HS, AW35HS, AW39HS, AW42HS, AW57HS, and AW60HS in between. Every frame size is available in both open loop and closed loop configurations, with custom shaft, connector, and winding options for OEM orders.
If you're not sure which frame fits your torque and speed requirements, send us your application details and our engineers will recommend a size rather than leaving you to guess from a datasheet.
Frequently Asked Questions
What is a NEMA 17 stepper motor used for?
NEMA 17 is the most common stepper motor size in desktop 3D printers, small CNC routers, and robotics joints, thanks to a practical balance of torque, size, and cost. It's typically the first frame size engineers reach for when a design doesn't have an unusual torque or space constraint.
Is a bigger NEMA size always stronger?
Generally yes when comparing across sizes, but not reliably within claims from different manufacturers — a longer-body NEMA 17 can out-torque a short-body NEMA 23 in some cases. Compare actual holding torque specifications, not just the NEMA number, when evaluating options.
Can I replace one NEMA size with another?
Only if the new motor's mounting bolt pattern, shaft diameter, and pilot boss match your existing mount, or if you're designing a new mounting plate. Changing NEMA size usually requires a new bracket or adapter plate, plus a driver capable of the new motor's current rating.
What does NEMA stand for?
NEMA stands for the National Electrical Manufacturers Association, a US standards body. The NEMA numbering convention used for stepper motor frame sizes is an industry-adopted shorthand for faceplate dimensions rather than an official stepper-motor-specific standard, but it is used consistently across most manufacturers worldwide.
Sources & Further Reading
● NEMA Stepper Motor Sizes, Specifications, and Frame Size Chart Explained — JLC Manufacturing — jlcmc.com
● Everything You Need to Know About Stepper Motors — RS Components — rs-online.com
● Stepper Motor Basics — AutomationDirect Technology Resources — automationdirect.com
● Stepper Motor Sizing Guide — Anaheim Automation — anaheimautomation.com
Motor Engineering Knowledge
What Is a Stepper Motor? A Beginner's Guide to How It Works
Stepper Motor vs Servo Motor: Which One Fits Your Application (coming next)
How to Calculate Holding Torque for a Stepper Motor (coming next)
Motor Technology Trends
Why Closed Loop Steppers Are Replacing Traditional Steppers
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