Choosing a poster size is a balance between visibility, content, and cost. Here is a practical guide.
The ISO A Sizes for Posters
- A0 — 841 × 1189 mm — large outdoor poster, viewed from 3–5 m
- A1 — 594 × 841 mm — conference poster, shop window, viewed from 1–2 m
- A2 — 420 × 594 mm — academic poster session, wall poster, viewed from 0.5–1 m
- A3 — 297 × 420 mm — small poster, notice board
Viewing Distance and Size
A good rule of thumb: body text should be readable at 1 metre for every 25 mm of cap height. So if your viewer stands 3 metres away, your body text needs to be at least 20–25 mm tall. Headlines should be 3–5× larger.
Posters viewed from close range (indoor, A2 or A3) can use smaller text (10–12 pt). Posters viewed from far away (A0 outdoor) may use headline text of 100 pt or more.
Resolution Requirements
For print, aim for 150 PPI at final size as a minimum, and 300 PPI for critical work. This means:
- 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
For outdoor posters, 72–100 PPI is often sufficient because viewers stand far away.
Cost Considerations
Poster printing cost scales with area. An A0 poster uses 4× the paper and ink of an A2. If budget is tight, choose A2 or A1. If impact is important (shop window, exhibition), A0 gives the biggest presence.
Custom Poster Sizes
Sometimes the standard sizes don't fit. Common custom formats:
- 2:3 ratio — e.g., 600 × 900 mm (close to A1)
- 3:4 ratio — e.g., 600 × 800 mm (close to A1 short)
- Cinema ratio — 27 × 40 inches for classic film posters
- Bus shelter — 1185 × 1750 mm (UK) or 1200 × 1800 mm (US)
Practical Checklist
- Decide viewing distance first
- Pick the smallest A size that works for that distance
- Add bleed of 3 mm on each side for printing
- Export at 150–300 PPI
- Test print on A4 to spot typos before the full size
All A series sizes are listed in our database with their pixel dimensions at both 150 and 300 DPI.