Choosing a poster size balances visibility, content, and cost. Here is a practical guide.
ISO A Sizes for Posters
- A0 — 841 × 1189 mm — large outdoor, viewed from 3–5 m
- A1 — 594 × 841 mm — conference poster, viewed from 1–2 m
- A2 — 420 × 594 mm — academic session, viewed from 0.5–1 m
- A3 — 297 × 420 mm — small poster, notice board
Viewing Distance and Size
Body text should be readable at 1 metre for every 25 mm of cap height. If your viewer stands 3 metres away, body text needs to be 20–25 mm tall.
Resolution Requirements
For print, aim for 150 PPI at final size as a minimum, and 300 PPI for critical work:
- A0 at 150 PPI: 4967 × 7022 px
- A1 at 150 PPI: 3508 × 4967 px
- A2 at 150 PPI: 2480 × 3508 px
- A3 at 150 PPI: 1754 × 2480 px
Cost Considerations
Cost scales with area. An A0 uses 4× the paper and ink of A2. If budget is tight, choose A2 or A1. If impact is important (shop window, exhibition), A0 gives biggest presence.
Custom Poster Sizes
- 2:3 ratio — e.g. 600 × 900 mm
- 3:4 ratio — e.g. 600 × 800 mm
- Cinema ratio — 27 × 40 in (classic film)
- Bus shelter — 1185 × 1750 mm (UK)
Checklist
- Decide viewing distance first
- Pick smallest A that works
- Add 3 mm bleed on each side
- Export at 150–300 PPI
- Test print on A4 to spot typos