Reference
Envelope sizes
The envelope you pick determines how the letter is folded. Choosing the wrong size means an extra fold, an awkward fit, or a letter that arrives creased. The reference below covers the envelopes used for most business and personal mail.
Not sure which one you need? The envelope finder works it out from your paper size and fold. To make one from a sheet of paper, the envelope template generator prints the cut and fold lines for any of these sizes, or for the card you need to send.
International (ISO)
C-series and DL
C-series envelopes are designed to hold the corresponding A-series sheet. C4 holds an A4 unfolded; C5 holds A4 folded once; C6 holds it folded twice. DL holds A4 folded into thirds.
DL
220 × 110 mm · 8.66 × 4.33 in
The standard business envelope across Europe and many other markets.
Fits
A4 folded into thirds
Read page →
C4
324 × 229 mm · 12.76 × 9.02 in
Holds A4 documents flat, without folding.
Fits
Unfolded A4
Reference only
C5
229 × 162 mm · 9.02 × 6.38 in
A common size for letters, statements and small booklets.
Fits
A4 folded once or unfolded A5
Read page →
C6
162 × 114 mm · 6.38 × 4.49 in
Postcard-style envelope. Suits greeting cards and short letters.
Fits
A4 folded twice or unfolded A6
Read page →
C6/C5
229 × 114 mm · 9.02 × 4.49 in
An elongated envelope, similar in role to DL but with C-series proportions.
Fits
A4 folded into thirds
Reference only
US sizes
Business and reply envelopes
US #9
98.4 × 225.4 mm · 3.87 × 8.87 in
A common reply envelope used inside US #10 envelopes.
Fits
Letter folded into thirds
Reference only
US #10
104.8 × 241.3 mm · 4.13 × 9.5 in
The standard business envelope in the United States.
Fits
US Letter folded into thirds
Read page →
US A2
111.13 × 146.05 mm · 4.38 × 5.75 in
The standard envelope for folded note cards and RSVP cards.
Fits
Letter folded into quarters (4.25 × 5.5 in cards)
Reference only
US A6
120.65 × 165.1 mm · 4.75 × 6.5 in
Sized for 4 × 6 photo cards and invitations.
Fits
4 × 6 in cards and photos
Reference only
US A7
133.35 × 184.15 mm · 5.25 × 7.25 in
The most common invitation envelope in the US.
Fits
5 × 7 in cards and invitations
Reference only
US A9
146.05 × 222.25 mm · 5.75 × 8.75 in
Takes a half-letter sheet without folding.
Fits
Half-letter (5.5 × 8.5 in) flat
Reference only
US Monarch (No. 7 ¾)
98.4 × 190.5 mm · 3.87 × 7.5 in
A slightly smaller and more formal US business envelope.
Fits
Monarch / executive stationery
Reference only