NEMA Motor Frame Size Chart (48–445T Dimensions)
NEMA frame sizes exist so a 215T motor from any manufacturer drops onto the same base with the same shaft. If you match the frame, the mounting dimensions match - which is what makes cross-brand motor replacement routine. The chart below covers the foot-mounted dimensions you need for a swap, in inches, per NEMA MG-1.
Foot-Mounted Frame Dimensions (inches)
| Frame | D (shaft height) | 2E (bolt width) | 2F (bolt length) | BA (shaft to front bolts) | U (shaft dia.) | N-W (shaft length) |
|---|---|---|---|---|---|---|
| 48 | 3.00 | 4.25 | 2.75 | 2.50 | 0.500 | 1.50 |
| 56 | 3.50 | 4.875 | 3.00 | 2.75 | 0.625 | 1.875 |
| 143T | 3.50 | 5.50 | 4.00 | 2.25 | 0.875 | 2.25 |
| 145T | 3.50 | 5.50 | 5.00 | 2.25 | 0.875 | 2.25 |
| 182T | 4.50 | 7.50 | 4.50 | 2.75 | 1.125 | 2.75 |
| 184T | 4.50 | 7.50 | 5.50 | 2.75 | 1.125 | 2.75 |
| 213T | 5.25 | 8.50 | 5.50 | 3.50 | 1.375 | 3.375 |
| 215T | 5.25 | 8.50 | 7.00 | 3.50 | 1.375 | 3.375 |
| 254T | 6.25 | 10.00 | 8.25 | 4.25 | 1.625 | 4.00 |
| 256T | 6.25 | 10.00 | 10.00 | 4.25 | 1.625 | 4.00 |
| 284T | 7.00 | 11.00 | 9.50 | 4.75 | 1.875 | 4.625 |
| 286T | 7.00 | 11.00 | 11.00 | 4.75 | 1.875 | 4.625 |
| 324T | 8.00 | 12.50 | 10.50 | 5.25 | 2.125 | 5.25 |
| 326T | 8.00 | 12.50 | 12.00 | 5.25 | 2.125 | 5.25 |
| 364T | 9.00 | 14.00 | 11.25 | 5.875 | 2.375 | 5.875 |
| 365T | 9.00 | 14.00 | 12.25 | 5.875 | 2.375 | 5.875 |
| 404T | 10.00 | 16.00 | 12.25 | 6.625 | 2.875 | 7.25 |
| 405T | 10.00 | 16.00 | 13.75 | 6.625 | 2.875 | 7.25 |
| 444T | 11.00 | 18.00 | 14.50 | 7.50 | 3.375 | 8.50 |
| 445T | 11.00 | 18.00 | 16.50 | 7.50 | 3.375 | 8.50 |
How to read it: D is the centerline height of the shaft above the mounting feet - the number that positions everything else. 2E and 2F locate the four mounting holes. U and N-W define the shaft you have to fit a sheave, sprocket, or coupling onto.
Decoding a Frame Number
- First two digits × ¼″ = D dimension. A 254T is 25÷4 = 6.25″ shaft height; a 326T is 8″.
- Third digit sets the foot bolt spacing (2F) - a 254T and 256T share height and shaft but the 256T feet sit farther apart.
- T suffix is the current (post-1964) standard. A U-frame motor of the same number is the older, larger design with a smaller shaft - a 254U does not interchange with a 254T without a base and sheave change.
- Fractional frames (48, 56) use a different scheme, and 56 variants (56H, 56HZ, 56J) add holes or shaft styles - 56J is the threaded-shaft jet pump pattern.
Matching Frame on a Replacement
Frame match answers the mechanical fit. You still confirm HP, RPM, voltage, enclosure, and service factor off the nameplate - our nameplate guide walks through it, and the cross-reference hub covers brand-to-brand swaps. Every product page in our motor catalog lists the frame size, so you can filter straight to a dimensional match. C-face and D-flange variants add a machined register on the drive end; flange kits convert many foot-mounted frames.
Frequently Asked Questions
What does the T mean in a motor frame size?
T designates the current NEMA standard dimensions adopted in 1964. T-frame motors of the same number are dimensionally interchangeable across manufacturers. The older U-frame series used more iron per horsepower and a smaller shaft, so U-to-T swaps need mounting and sheave checks.
How do I find shaft height from the frame number?
Divide the first two digits by four. A 184T has a 4.5-inch shaft height (18/4), a 326T has 8 inches (32/4). This D dimension is measured from the bottom of the feet to the shaft centerline.
What is the difference between a 254T and a 256T frame?
Shaft height, shaft diameter, and bolt width are identical; only the 2F foot-bolt spacing differs - 8.25 inches on the 254T versus 10 inches on the 256T. The longer frame typically carries the higher HP rating at a given speed.
Are 56 frame and 143T interchangeable?
They share the 3.5-inch shaft height, but bolt patterns and shaft diameters differ - 0.625-inch shaft on the 56 versus 0.875 on the 143T. Combination 56H bases drill for both patterns, and adapter bases handle the rest.
Does frame size tell me the horsepower?
No. Frame standardizes dimensions, not ratings - a 215T might be 10 HP at 1800 RPM or 15 HP at 3600 RPM, and premium designs sometimes package more HP in a frame. Always confirm HP and RPM from the nameplate.
Related Resources
- Electric Motors by Frame
- How to Read a Motor Nameplate
- Motor Cross-Reference Hub
- Motor Slide Bases
- Flange Kits & Accessories
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