Find the right envelope.
Start with what goes inside. We’ll help you find the fit.
For thick stacks or padded items, use a roomier envelope and check its inside dimensions.
Smallest standard fit
#10 9½ × 4⅛ in
Fold it into three equal panels.
Other sizes that fit
Keep this handy
Envelope sizes at a glance
| Envelope | Size (in) | Common use | Mailing check |
|---|---|---|---|
| #6 1/4Checks and small business forms | 6 × 3.5 | Checks and small business forms | |
| #6 3/4Personal checks and small inserts | 6.5 × 3.625 | Personal checks and small inserts | |
| Monarch (#7 3/4)Executive correspondence | 7.5 × 3.875 | Executive correspondence | |
| #9Reply and remittance mail | 8.875 × 3.875 | Reply and remittance mail | |
| #10Standard tri-folded US Letter paper | 9.5 × 4.125 | Standard tri-folded US Letter paper | |
| #11Bulkier folded business documents | 10.375 × 4.5 | Bulkier folded business documents | |
| #12Larger folded business documents | 11 × 4.75 | Larger folded business documents | |
| #14Large folded forms and documents | 11.5 × 5 | Large folded forms and documents | |
| A1RSVP and small note cards | 5.125 × 3.625 | RSVP and small note cards | |
| A2Invitations and 4.25 × 5.5 cards | 5.75 × 4.375 | Invitations and 4.25 × 5.5 cards | |
| A6Invitations and 4.5 × 6.25 cards | 6.5 × 4.75 | Invitations and 4.5 × 6.25 cards | |
| A75 × 7 invitations and greeting cards | 7.25 × 5.25 | 5 × 7 invitations and greeting cards | |
| A8Large invitations and cards | 8.125 × 5.5 | Large invitations and cards | |
| A9Half-folded US Letter paper | 8.75 × 5.75 | Half-folded US Letter paper | |
| A10Oversized announcements and cards | 9.5 × 6 | Oversized announcements and cards | |
| 6 × 9 BookletHalf-folded US Letter paper and booklets | 9 × 6 | Half-folded US Letter paper and booklets | |
| 9 × 12 CatalogUS Letter paper without folding | 12 × 9 | US Letter paper without folding | |
| 10 × 13 CatalogThick document sets and catalogs | 13 × 10 | Thick document sets and catalogs | |
| 5 × 5 SquareSquare invitations and cards | 5 × 5 | Square invitations and cards | |
| 6 × 6 SquareSquare invitations and photos | 6 × 6 | Square invitations and photos | |
| 7 × 7 SquareLarge square invitations | 7 × 7 | Large square invitations | |
| C7A7 paper or small cards | 4.488 × 3.189 | A7 paper or small cards | |
| C6A6 paper or quarter-folded A4 paper | 6.378 × 4.488 | A6 paper or quarter-folded A4 paper | |
| DLTri-folded A4 paper | 8.661 × 4.331 | Tri-folded A4 paper | |
| C5A5 or half-folded A4 paper | 9.016 × 6.378 | A5 or half-folded A4 paper | |
| C4A4 paper without folding | 12.756 × 9.016 | A4 paper without folding |
These are outside measurements; there’s slightly less room inside. Check the measurements before buying, since similar size names can mean different things.
Will my paper fit in the suggested envelope?
We suggest envelopes a little bigger than your paper so it has room to slide in. For a thick stack of paper or a padded envelope, go up a size and check the space inside before buying.
Will it mail with a regular stamp?
Size alone cannot tell you. Weight, thickness, rigidity, and shape affect postage. Use the mailing check above, then the postage calculator for the price.
We use USPS rules to check your envelope’s size and shape.
USPS size limits ↗What USPS allows in the mail ↗