Introduction
Identifying the IEC frame size of an existing motor is not always straightforward, particularly where the frame size is unclear or not shown on the motor nameplate. One useful way to help identify the motor is to check its shaft dimensions and compare them with the standard IEC dimensions shown in the table below.
The shaft diameter, shaft extension and key size can provide a useful indication of the motor frame size and can also help confirm whether a replacement motor is likely to be mechanically compatible with the existing installation.
This table should be used as a reference guide rather than as the only method of identifying a motor. Wherever possible, also check the motor nameplate, mounting arrangement and other critical dimensions before selecting a replacement.
⚠️ Important: Motors fitted to pumps, gearboxes and other machinery may have modified, extended or specially adapted shafts. The dimensions below apply to standard, unmodified IEC motors and should not be relied upon where the original motor has been mechanically altered. ⚠️
IEC Motor Frame Size vs Shaft Size Dimensions
This table provides commonly used reference dimensions for IEC metric motor frame sizes. Always confirm critical dimensions against the motor manufacturer's dimensional drawing before selecting or replacing a motor.
Common IEC motor frame sizes and corresponding shaft dimensions
| IEC Frame Size |
Shaft Centre Height H (mm) |
Shaft Diameter D (mm) |
Shaft Extension E (mm) |
Key Size W × H (mm) |
| 63 |
63 |
11 |
23 |
4 × 4 |
| 71 |
71 |
14 |
30 |
5 × 5 |
| 80 |
80 |
19 |
40 |
6 × 6 |
| 90S / 90L |
90 |
24 |
50 |
8 × 7 |
| 100L |
100 |
28 |
60 |
8 × 7 |
| 112M |
112 |
28 |
60 |
8 × 7 |
| 132S / 132M |
132 |
38 |
80 |
10 × 8 |
| 160M / 160L |
160 |
42 |
110 |
12 × 8 |
| 180M / 180L |
180 |
48 |
110 |
14 × 9 |
| 200L |
200 |
55 |
110 |
16 × 10 |
| 225S / 225M |
225 |
60 |
140 |
18 × 11 |
| 250M |
250 |
65 |
140 |
18 × 11 |
| 280S / 280M |
280 |
75 |
140 |
20 × 12 |
| 315S / 315M / 315L |
315 |
80 |
170 |
22 × 14 |
| 355M / 355L |
355 |
100 |
210 |
28 × 16 |
Useful Information
- ℹ️ The IEC frame number corresponds to the nominal shaft centre height in millimetres for a standard foot-mounted motor. For example, a frame 132 motor has a nominal shaft centre height H of 132 mm.
- ℹ️ Letters following the frame number, such as S, M or L, generally distinguish different motor body lengths within the same shaft-height range.
- ℹ️ Dimensions may vary for special motors such as brake motors, hazardous-area motors, reduced-frame designs or manufacturer-specific constructions. We do not supply hazardous-area motors.
Useful Links
How to read a motor nameplate to determine key VSD parameters
Star and Delta motor connections
IEC Motor Frame Size vs Shaft Size
All details including drawings and photos are created by Inverter Drive Supermarket - last revised August 2026