DL Envelope
C-Series Envelopes (ISO 269) · 7 specs
Direct Answer
The DL envelope (Dimension Lengthwise / DIN Lang, standardized under ISO 269 and DIN 678) measures 110 × 220 mm (4.33 × 8.66 inches). Engineered specifically to hold an A4 sheet folded horizontally in thirds (Z-fold or C-fold), it is the dominant standard across Europe and most of the world for automated corporate billing, bank statements, and commercial direct-mail advertising.
Source: ISO 269:1985 / DIN 678 (Format DL) · Last reviewed Aug 28, 2026
Specs
| Width × Height (Metric) | 110 × 220 mm |
| Width × Height (Imperial) | 4.33 × 8.66 in |
| Target Paper Pairing | Standard A4 sheet folded in thirds horizontally (99 × 210 mm) |
| Paper Insertion Clearance | +11 mm height / +10 mm width clearance |
| Address Window Position | Standard DIN window: 45 × 90 mm, located 20 mm from left, 15 mm from bottom |
| Automated Insertion Standard | High-speed optical inserter machine standard (thousands of pieces/hour) |
| Comparison to US #10 | DL is 110 × 220 mm; US #10 is 4.125 × 9.5 in (104.8 × 241.3 mm) |
The Corporate Mail Workhorse
When an A4 sheet (210 × 297 mm) is folded horizontally in thirds (each section measuring 210 × 99 mm), it slides effortlessly into a DL envelope (110 × 220 mm). Combined with standard address windows aligned with corporate letterhead templates, DL envelopes eliminate the need to print separate address labels.
DL vs North American #10 Envelope
- ISO DL Envelope: 110 × 220 mm (4.33 × 8.66 in) — designed for tri-folded A4.
- US #10 Envelope: 104.8 × 241.3 mm (4.125 × 9.50 in) — designed for tri-folded US Letter (8.5 × 11 in).
An A4 sheet tri-folded will fit into a US #10 envelope, but a US Letter tri-folded (8.5 in = 215.9 mm) is too tight for manual stuffing in some DL envelopes.