A4, A5, DL — UK print sizing looks arbitrary until you see the logic. Two minutes here saves you ordering the wrong size or downloading the wrong template.
The A-Series Logic: Every Size Is Half the One Above
The international ISO 216 standard is built on one elegant trick: every A-size has the same proportions (a width-to-height ratio of √2, about 1:1.414), which means folding or cutting any sheet in half gives you the next size down with identical proportions. A0 is defined as one square metre of paper; halve it and you get A1, halve again for A2, and so on.
| Size | Dimensions | Common print uses |
|---|---|---|
| A0 | 841 × 1189mm | Large posters, wall planners |
| A1 | 594 × 841mm | Posters, planners |
| A2 | 420 × 594mm | Posters, planners |
| A3 | 297 × 420mm | Wall calendars, small posters, folded-to-A4 brochures |
| A4 | 210 × 297mm | Letterheads, booklets, leaflets |
| A5 | 148 × 210mm | Leaflets, booklets, strut cards |
| A6 | 105 × 148mm | Postcards, small leaflets |
What Is DL?
DL is 99 × 210mm — exactly one-third of an A4 sheet. It exists so an A4 letter folded in three, or an unfolded compliment slip, slides perfectly into a DL envelope. It's the standard for compliment slips, rack leaflets and tri-fold brochures.
Envelope Pairing (C-Series)
Envelopes run on the matching C-series, each sized to take the same-numbered A-sheet: C4 takes flat A4, C5 takes A5 (or A4 folded once), and DL envelopes take a DL slip or A4 folded in three.
The US Template Trap
US sizes are different: US Letter is 8.5 × 11in (216 × 279mm) — wider and shorter than A4 — and US business cards are 3.5 × 2in (89 × 51mm) vs the UK's 85 × 55mm. If you download a template from a US website, your artwork will be the wrong size for UK printing. Always start from a UK/ISO template — ask us and we'll send the correct one for your product. Browse our full business stationery & publications range.
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