When you need to send out letters, invitations, or any other correspondence en masse, you want to make sure that you get the envelope size(s) right. While you can make most kinds of printer paper fit in standard envelope sizes, you might have to use some creative folding techniques, especially if you’re sending more than one document in each envelope. Moreover, if you’re using cardstock or similarly thick paper for invitations or announcements, you’ll need to make sure that you get the envelope size exactly right.
In today’s guide, we’re going to look at the dimensions and common uses for different kinds of envelopes. And remember, if you’re currently in need of envelopes for business or personal use, be sure to check out all we have to offer at Fine Cardstock today!
Standard Envelope Sizes
In the United States, standard envelope sizes are designated by numbers ranging from #5 to #14. The lowest numbers on the scale refer to envelopes with smaller dimensions, while the highest numbers on the scale refer to envelopes with larger dimensions. You can find the precise dimensions for these standard envelope sizes in the table below:
| Number | Height/Width (in) | Height/Width (mm) |
| #5 | 3.125 x 5.5 | 79 x 139 |
| #6-1/4 | 3.5 x 6 | 89 x 152 |
| #6-3/4 | 3.625 x 6.5 | 92 x 165 |
| #7 | 3.75 x 6.75 | 95 x 171 |
| #7-1/2 | 3.875 x 7.5 | 98 x 191 |
| #8-5/8 | 3.625 x 8.625 | 92 x 219 |
| #9 | 3.875 x 8.875 | 98 x 225 |
| #10 | 4.125 x 9.5 | 105 x 241 |
| #11 | 4.5 x 10.375 | 114 x 264 |
| #12 | 4.75 x 11 | 121 x 279 |
| #14 | 5 x 11.5 | 127 x 292 |
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#5 Envelopes#5 is the smallest among the standard envelope sizes in the United States. Measuring 3.125 inches tall and 5.5 inches wide, the #5 envelope is ideal for personal stationery and small notes. But as previously mentioned, if you’re using thin paper or special folding techniques, you can still use #5 (and many other sizes) for a wide range of purposes. |
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#6-1/4 Envelopes#6-1/4 is the next size up from #5 envelopes. Measuring 3.5 inches tall and 6 inches wide, this size envelope works well for standard letters or greeting cards. |
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#6-3/4 Envelopes#6-3/4 is another standard envelope that you will commonly see in your mailbox, particularly if you run a business. Measuring 3.625 inches tall and 6.5 inches wide, this envelope is often used for checks, invoices, and official documents. |
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#7 Envelopes#7 is slightly larger than the #6-3/4 envelope. It measures 3.75 inches tall and 6.75 inches wide. While #7 can be used for many different kinds of letters and messages, it is ideal for announcements and greeting cards. |
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#7-1/2 Envelopes#7-1/2 is another envelope that is commonly used by businesses of all sizes. The #7-1/2 measures 3.875 inches tall and 7.5 inches wide. The additional width makes it ideal for larger invoices, memos, and financial reports. |
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#8-5/8 EnvelopesGenerally, as the size increases among standard envelopes, they become more beneficial for commercial use and less beneficial for personal use. The #8-5/8 envelope is no exception. Measuring 3.625 inches tall and 8.625 inches wide, this envelope works well for checks or documentation that requires larger pieces of paper. |
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#9 EnvelopesThe #9 envelope is another size that works very well for businesses. Measuring 3.875 inches tall and 8.875 inches wide, this size is most often used for business reply envelopes. These envelopes can easily fit inside a #10 envelope, making it easy to send out notifications to consumers so that they can quickly respond by mail. |
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#10 EnvelopesThe #10 is the most popular size for standard business letters. Measuring 4.125 inches tall and 9.5 inches wide, this envelope can fit most types of commercial documentation — from credit card offers to promotional announcements. |
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#11 Envelopes#11 measures 4.5 inches tall and 10.375 inches wide. This makes it a good fit for large documents or correspondence that have multiple pages, like product catalogs. |
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#12 Envelopes#12 is one of the largest standard envelopes for business use. Due to its large size (4.75 inches x 11 inches), #12 is perfect for mail that has more than 2-3 folded pages inside. This might include contracts or legal forms. |
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#14 EnvelopesFinally, #14 is the largest of the standard-sized U.S. envelopes. The #14 measures 5 inches tall and 11.5 inches wide, and is generally reserved for larger packets of paper, brochures, or other documents that need to be folded to fit properly. |
Invitation Envelope Sizes
In addition to the standard personal and commercial envelopes outlined above, you can also choose from various sizes designed specifically for things like special announcements, greeting cards, and invitations. You can find the dimensions for these envelopes in the table below:
| Number | Height/Width (in) | Height/Width (mm) |
| A2 | 4.375 x 5.75 | 111 x 146 |
| A6 | 4.75 x 6.5 | 120 x 165 |
| A7 | 5.25 x 7.25 | 133 x 184 |
| 5×5 (Square) | 5 x 5 | 127 x 127 |
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A2 EnvelopesA2 is the shortest of the invitation envelopes, but not necessarily the smallest. Measuring 4.375 inches tall and 5.75 inches wide, the A2 is a good size for thank you messages, RSVP cards, and smaller invitations. |
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A6 EnvelopesThe A6 invitation envelope measures 4.75 inches tall and 6.5 inches wide. This height-to-width ratio makes it ideal for most kinds of invitations and announcements, as well as special photos. |
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A7 EnvelopesA7 is the largest of the invitation envelopes, measuring 5.25 inches tall and 7.25 inches wide. This is a very popular option for wedding invitations, baby shower invitations, and other important event messages that typically require a response. |
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5×5 (Square) EnvelopesAs the name implies, the 5×5 is a perfectly square invitation envelope. It can work for many different announcements and invitations, but it is specifically designed to be paired with square paper or cardstock. |
Standard Catalog and Booklet Envelope Sizes
If you need to send out large packets of information, booklets, or brochures, you may need to rely on envelopes that are specifically designed to handle the extra size and weight. You can either choose booklet envelopes, which have a flap on the longer side, or catalog envelopes, which have a flap on the shorter side. In the sections below, we will take a closer look at the three standard catalog and booklet envelope sizes:
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6×9 EnvelopesAs the name indicates, this envelope measures 6 inches by 9 inches (152 mm x 229 mm). As the smallest among the catalog and booklet envelopes, this size works best for relatively small brochures and documents. 6×9 can also be used for direct mail campaigns and promotional materials. |
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9×12 EnvelopesThe 9×12 envelope measures 9 inches by 12 inches (229 mm x 305 mm). Since it is roughly 33% larger than the 6×9 envelope, it can handle much larger documents and packets. These envelopes are frequently used to send presentation material, as the envelopes are large enough to contain a lot of paper without the need for excessive folding. |
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10×13 EnvelopesThe 10×13 measures 10 inches by 13 inches (254 mm x 330 mm). As the largest of all the catalog or booklet envelopes, the 10×13 can fit larger documents with just one fold or no folds at all. The size helps make 10×13 good for contracts and other important documents that cannot be disfigured in transit. |
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