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US Envelope Sizes: #10 Fits a Letter Folded in Thirds, A7 Fits a 5×7 Card
The five envelopes compared
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Industry standard
#10 business envelope
4 1/8 × 9 1/2 in (104.8 × 241.3 mm)
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Industry standard
#9 reply envelope
3 7/8 × 8 7/8 in (98.4 × 225.4 mm)
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Industry standard
#6¾ remittance envelope
3 5/8 × 6 1/2 in (92.1 × 165.1 mm)
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Industry standard
A2 invitation envelope
4 3/8 × 5 3/4 in (111.1 × 146.1 mm)
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Industry standard
A7 invitation envelope
5 1/4 × 7 1/4 in (133.4 × 184.2 mm)
The short answer
- #104 1/8 × 9 1/2 in (104.8 × 241.3 mm) — holds a Letter sheet folded in thirds
- #93 7/8 × 8 7/8 in (98.4 × 225.4 mm) — fits inside a #10 as a reply envelope
- #6¾3 5/8 × 6 1/2 in (92.1 × 165.1 mm) — Remittance; holds checks and payment slips
- A24 3/8 × 5 3/4 in (111.1 × 146.1 mm) — holds an A2 note card (4 1/4 × 5 1/2 in)
- A75 1/4 × 7 1/4 in (133.4 × 184.2 mm) — standard for 5×7 in greeting cards and invitations
See the sizes in AR (shown as boxes)
The four sizes as boxes at their published dimensions
Preparing 3D…
1 #102 #93 A24 A7
On a phone, the "View in your room (AR)" button places the boxes in your room. The boxes are locked to the published dimensions and cannot be resized. They show size only and are not 3D replicas of the products.
Drawn to the same scale
Dimensions side by side
| Size | Inches (W × H) | Millimeters (W × H) | What goes inside |
|---|---|---|---|
| #10 | 4 1/8 × 9 1/2 in | 104.8 × 241.3 mm | US Letter folded in thirds (8.5 × 3.67 in) |
| #9 | 3 7/8 × 8 7/8 in | 98.4 × 225.4 mm | Fits inside a #10 as a reply envelope |
| #6¾ | 3 5/8 × 6 1/2 in | 92.1 × 165.1 mm | Checks, payment slips, remittance stubs |
| A2 | 4 3/8 × 5 3/4 in | 111.1 × 146.1 mm | A2 note card (4 1/4 × 5 1/2 in / 108 × 140 mm) |
| A7 | 5 1/4 × 7 1/4 in | 133.4 × 184.2 mm | 5×7 in card (127 × 178 mm) |
Millimeter values are converted at 1 in = 25.4 mm and rounded to one decimal place. Dimensions are nominal; actual envelopes vary slightly by manufacturer and paper thickness.
What the numbers mean
The #10 is the most mailed envelope in the US. A US Letter sheet (8.5 × 11 in) folded in thirds produces a panel 8.5 × 3.67 in wide. That fits the #10's 9.5 in length with 1 in to spare and the 4.125 in height with about 1/4 in on each side.
The #9 is designed to slip inside a #10. Its 8.875 in length fits inside the 9.5 in #10 with 5/8 in of clearance at the top. Its 3.875 in width leaves 1/4 in of clearance on each side. Pre-printed #9 return envelopes are mailed flat inside a #10 so the recipient can fold and mail them back.
A7 is the industry standard for 5×7 in formal invitations and greeting cards. The 5×7 card (127 × 178 mm) fits inside the 5.25 × 7.25 in A7 (133.4 × 184.2 mm) with about 1/4 in of clearance on each edge. A2 fills the same role for smaller enclosures: an A2 note card (4 1/4 × 5 1/2 in) fits inside the 4 3/8 × 5 3/4 in envelope with about 1/8 in of clearance per side.
The #6¾ (Remittance envelope) is shorter than the other commercial sizes and fits payment stubs, checks, and folded forms. The USPS Domestic Mail Manual Section 101 sets the minimum mailable letter size at 5 × 3.5 in; all five envelopes here meet that minimum and fall within the maximum of 11.5 × 6.125 in.
Product links
FAQ
What size is a #10 envelope?
A #10 business envelope measures 4 1/8 × 9 1/2 in (104.8 × 241.3 mm). It is the most common mailing envelope in the US and fits a standard US Letter sheet (8.5×11 in) folded in thirds.
Does a #9 envelope fit inside a #10?
Yes. A #9 envelope (3 7/8 × 8 7/8 in / 98.4 × 225.4 mm) fits inside a #10 (4 1/8 × 9 1/2 in / 104.8 × 241.3 mm), leaving about 1/4 in of clearance on each side and 5/8 in at the top. #9 envelopes are used as pre-addressed reply envelopes mailed inside a #10.
What fits in an A7 envelope?
An A7 envelope (5 1/4 × 7 1/4 in / 133.4 × 184.2 mm) is the standard size for a 5×7 in greeting card or formal invitation. The card slides in with about 1/4 in of clearance on each edge.
What is a #6¾ envelope used for?
The #6¾ envelope (3 5/8 × 6 1/2 in / 92.1 × 165.1 mm) is also called a Remittance envelope. It is commonly used for billing statements, checks, and return payment slips.
What size card fits in an A2 envelope?
An A2 envelope (4 3/8 × 5 3/4 in / 111.1 × 146.1 mm) fits a standard A2 note card (4 1/4 × 5 1/2 in / 108 × 140 mm) with about 1/8 in of clearance on each side. A2 envelopes are used for RSVP cards, gift enclosures, and small invitations.
See also: 9×12 vs 10×13 Catalog Envelopes — the open-end sizes that hold a Letter sheet flat. USPS Flat Rate Box Sizes — Small, Medium, and Large interior and exterior dimensions. A4 vs Letter — the paper that goes inside a #10. ANSI Paper Sizes A–E — the full ANSI series from Letter to E.
Sources
- #10, #9, #6¾, A2, A7 dimensions: envelopes.com Envelope Size Guide, envelopes.com/pages/envelope-size-guide, checked 2026-10-03. A2 dimension also confirmed at envelopes.com/collections/envelopes-by-size-a2, checked 2026-10-03.
- USPS mailing size standards: USPS Domestic Mail Manual Section 101, pe.usps.com/text/dmm300/101.htm. Letter-size minimum 5 × 3.5 in, maximum 11.5 × 6.125 in.
- US Letter sheet dimensions: ASME Y14.1, 8.5 × 11 in (215.9 × 279.4 mm).
- 5×7 card dimensions: ISO/IEC 7810 does not cover cards of this size; 5×7 is an industry convention confirmed by photo-print manufacturers (Shutterfly, Walgreens). See also Photo Print Sizes.