Envelope · International
DL envelope
The DL envelope is 220 × 110 mm and is the most common business envelope across Europe, the UK and the Commonwealth. It is designed to hold a standard A4 sheet folded into thirds — the format used for invoices, statements, contracts and most business correspondence.
Exact dimensions
DL is part of the ISO 269 C-series of envelopes, even though its proportions are derived from folding A4 into thirds rather than directly from the C-series mathematics. The fit is generous: an A4 folded into thirds is roughly 210 × 99 mm, leaving 10 mm of clearance both ways.
| Unit | Width | Height |
|---|---|---|
| Millimetres (mm) | 220 | 110 |
| Centimetres (cm) | 22 | 11 |
| Inches (in) | 8.661 | 4.331 |
DL — 220 × 110 mm
What it's for
- · A4 business letters folded into thirds
- · Invoices and statements
- · Mailshots and direct marketing
- · Cheques and remittance slips
- · Cover letters with a small enclosure
Window envelopes
Many DL envelopes have a clear cellophane window that displays the recipient address from the letter inside. If you design A4 letters intended for window-DL envelopes, place the address block in a standardised position: roughly 50 mm from the left edge and 50 mm from the top of the letter. Many word processors include a "DL window envelope" template that uses this position.
Printing & mailing notes
Postal sorting machines read the bottom strip of the front face — keep roughly the lowest 15 mm clear of graphics and text so franking marks and routing codes have somewhere to land. DL travels at the standard letter tier with most European postal services, which is precisely why it became the default business envelope: maximum A4 content, minimum postage.
The tri-fold that fills it: an A4 sheet folded at 99 mm intervals gives three 210 × 99 mm panels that drop into the 220 × 110 mm pocket with about 5 mm of clearance on each axis — enough to insert by hand without fighting the paper.
Frequently asked questions
What does "DL" stand for?
"DL" stands for "Dimension Lengthwise". The DL envelope is defined by ISO 269 and is the most common business envelope size across Europe and the Commonwealth.
What fits inside a DL envelope?
A standard A4 sheet (210 × 297 mm) folded into thirds along the long edge fits comfortably. Each fold reduces the height to 99 mm, leaving roughly 10 mm of clearance inside the 110 mm tall envelope.
How do I fold A4 to fit a DL envelope?
Lay the A4 sheet flat, fold the bottom third up over the middle third, then fold the top third down. The result is roughly 210 × 99 mm — slightly smaller than the 220 × 110 mm DL envelope opening.
Is DL the same as a US #10 envelope?
No. The US #10 is 241.3 × 104.8 mm — longer and narrower than DL. They serve the same role (business letters folded into thirds) but the underlying paper sizes (A4 vs Letter) make them noticeably different.
What weight of paper works for a DL envelope?
80–100 gsm is the standard for office DL envelopes. Heavier 120 gsm paper is sometimes used for premium or branded business mail, but check that your printer can feed thicker stock.
What does DL stand for?
Dimension Lengthwise (often read as “DIN lang”), from the German DIN envelope family that was adopted alongside the ISO C-series. DL is not itself a C-size — its ISO-proportioned cousin is C6/C5 (229 × 114 mm), which does the same tri-fold job with a little more clearance.
Where does the address window go on a DL envelope?
The common convention is a window of roughly 90 × 45 mm toward the lower left of the front; exact placement varies by national post — the German DIN 680 layout, for example, sets it 20 mm from the left edge and 15 mm up from the bottom. Match the window position your local supplier stocks, then place the letter’s address block to line up with it after the tri-fold.
Can a home printer print on DL envelopes?
Yes. Feed envelopes one at a time through the manual/bypass slot, set the paper size to DL (or a custom 110 × 220 mm), and check the printer manual for flap orientation — getting it backwards mirrors the layout. Straight paper paths (rear feed) jam far less than U-turn paths.
DL or C6/C5 — which should I buy?
For everyday tri-folded A4 letters they are interchangeable and DL is the cheaper, more widely stocked default. Choose C6/C5 when the insert is stiff or thick (card stock, stapled sets) — the extra 9 mm of length and 4 mm of height make machine inserting and hand stuffing noticeably easier.