Physical standards for machinable mail
Post card (First class only)
Letters (all classes)
Flats (all classes)
| Postcard dimensions |
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Minimum | Maximum | |
| Length |
5 inches |
6 inches |
|
| Height |
3 1/2 inches |
4 1/4 inches |
|
| Thickness |
0.007 inch |
0.016 inch |
|
| Letter dimensions |
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Minimum | Maximum | |
| Length |
5 inches |
11 1/2 inches |
|
| Height |
3 1/2 inches |
6 1/8 inches |
|
| Thickness |
0.007 inch |
1/4 inch |
|
| Flats dimensions |
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![]() |
Minimum | Maximum | |
| Length |
11 1/2 inches |
15 inches |
|
| Height |
6 1/8 inches |
12 inches |
|
| Thickness |
1/4 inch | 3/4 inch |
|



Direct Mail Services
