NEMA Motor Frame Chart — Shaft Height, Shaft Diameter & Mounting Dims
NEMA motor frame dimensions for 143T-445T frames: shaft height computed from the frame number, plus shaft diameter and mounting dimensions.
Updated August 22, 2026
The entire point of the NEMA frame system (MG-1) is that a 184T motor from any manufacturer drops onto the same feet, at the same height, with the same shaft. The frame number even encodes the geometry: divide the first two digits by four and you get D, the shaft centerline height above the feet, in inches — 143T is 3.5 in, 254T is 6.25 in, 445T is 11 in. That column below is computed from the identity, not copied. The trailing digit distinguishes short and long foot patterns (184T is a longer-footed 182T; same D, same shaft), and the T suffix marks the modern (post-1964) frame generation with its larger shafts.
The transcribed columns are the ones you need to swap or mount a motor: U is the shaft diameter, N-W the usable shaft extension, 2E the bolt-hole spread across the shaft axis (E is its half, measured from centerline), 2F the spread along the axis — the dimension that changes within a frame pair — and BA the distance from the shaft-end bolt holes to the shaft shoulder, which sets whether a pulley lines up after a swap. Everything here is the foot-mounted T-frame table; TS (short-shaft), C-face (TC), and U-frame variants share mounting feet but differ at the shaft — see the FAQ before assuming interchangeability.
NEMA T-Frame Dimensions, 143T–445T (Foot-Mounted, inches)
| Frame | D — shaft height (computed) | 2E — bolt spread across (in) | 2F — bolt spread along (in) | BA (in) | U — shaft Ø (in) | N-W — shaft extension (in) |
|---|---|---|---|---|---|---|
| 143T | 3.50 | 5.50 | 4.00 | 2.25 | 0.8750 | 2.25 |
| 145T | 3.50 | 5.50 | 5.00 | 2.25 | 0.8750 | 2.25 |
| 182T | 4.50 | 7.50 | 4.50 | 2.75 | 1.1250 | 2.75 |
| 184T | 4.50 | 7.50 | 5.50 | 2.75 | 1.1250 | 2.75 |
| 213T | 5.25 | 8.50 | 5.50 | 3.50 | 1.3750 | 3.38 |
| 215T | 5.25 | 8.50 | 7.00 | 3.50 | 1.3750 | 3.38 |
| 254T | 6.25 | 10.00 | 8.25 | 4.25 | 1.6250 | 4.00 |
| 256T | 6.25 | 10.00 | 10.00 | 4.25 | 1.6250 | 4.00 |
| 284T | 7.00 | 11.00 | 9.50 | 4.75 | 1.8750 | 4.62 |
| 286T | 7.00 | 11.00 | 11.00 | 4.75 | 1.8750 | 4.62 |
| 324T | 8.00 | 12.50 | 10.50 | 5.25 | 2.1250 | 5.25 |
| 326T | 8.00 | 12.50 | 12.00 | 5.25 | 2.1250 | 5.25 |
| 364T | 9.00 | 14.00 | 11.25 | 5.88 | 2.3750 | 5.88 |
| 365T | 9.00 | 14.00 | 12.25 | 5.88 | 2.3750 | 5.88 |
| 404T | 10.00 | 16.00 | 12.25 | 6.62 | 2.8750 | 7.25 |
| 405T | 10.00 | 16.00 | 13.75 | 6.62 | 2.8750 | 7.25 |
| 444T | 11.00 | 18.00 | 14.50 | 7.50 | 3.3750 | 8.50 |
| 445T | 11.00 | 18.00 | 16.50 | 7.50 | 3.3750 | 8.50 |
D computed from the MG-1 frame-number identity (first two digits ÷ 4); 2E computed as 2 × the transcribed E. Keyseat widths are omitted — the consulted reproductions could not be digit-verified against each other for every row. TS suffix frames share these feet with shorter shafts; TC adds a C-face.
Sources & Further Reading
- NEMA MG-1 (Motors and Generators), 4.4.1 frame dimension tables, as reproduced in the Lewis Motor Repair NEMA frame dimension chart (which cites MG 1-2011 directly)
- Leeson/Regal “Quick Reference Motor Dimensions” NEMA data chart (independent digit-verification of D, E, 2F, BA, U, N-W for 143T–405T); Grainger/Baldor NEMA dimension charts (444T/445T BA confirmation); turn2engineering T-frame chart (D/E/2F/U cross-check)
- D = frame digits ÷ 4 and 2E = 2·E are arithmetic identities, computed in code
Frequently Asked Questions
Can I replace a motor with another brand in the same frame size?
Yes — that is what MG-1 standardizes. Two 256T motors interchange dimensionally regardless of manufacturer: same 6.25 in shaft height, same 10 × 10 in bolt pattern (2E × 2F), same 1.625 in shaft. What MG-1 does not standardize is everything else — conduit box position, overall length, weight, and electrical characteristics — so check the belt guard and wiring clearances even when the feet line up.
What is the difference between 182T and 184T?
Only the foot spacing along the shaft: both are 4.5 in shaft height with a 1.125 in shaft and 7.5 in bolt spread across, but the 182T feet are on a 4.5 in longitudinal spacing and the 184T on 5.5 in. The longer variant of a pair generally carries the higher horsepower rating for the same speed. If your base has slotted rails, either fits; on a drilled pattern the pair are not interchangeable.
What do the T, TS, U, and C suffixes mean?
T marks the 1964-and-later frame assignments in this chart. TS is the same frame with a short shaft (for direct coupling only — a 324TS shaft is both shorter and thinner than a 324T, so it cannot take a belt drive). U frames are the older 1952-era assignments: same D for the same leading digits but different, generally smaller shafts — a 254U has a 1.375 in shaft where the 254T has 1.625 in. C (as in 184TC) adds a standardized C-face flange on top of the foot mount.
How do I identify a motor frame with a tape measure?
Measure D, the centerline height above the mounting feet: multiply by 4 and you have the frame’s first two digits (5.25 in → 21x). Then measure the foot bolt spacing along the shaft (2F) and match it in the table to split, say, 213T from 215T. Confirm with the shaft diameter — U changes between T and U generations even when the feet match. The nameplate is definitive, but this gets you the frame when the plate is gone.
Try the Calculators
NEMA Motor Frame Chart — Shaft Height, Shaft Diameter & Mounting Dims — reuven.tools/reference/nema-motor-frames — verified against: NEMA MG-1 (Motors and Generators), 4.4.1 frame dimension tables, as reproduced in the Lewis Motor Repair NEMA frame dimension chart (which cites MG 1-2011 directly); Leeson/Regal “Quick Reference Motor Dimensions” NEMA data chart (independent digit-verification of D, E, 2F, BA, U, N-W for 143T–405T); Grainger/Baldor NEMA dimension charts (444T/445T BA confirmation); turn2engineering T-frame chart (D/E/2F/U cross-check); D = frame digits ÷ 4 and 2E = 2·E are arithmetic identities, computed in code