What Resolution You Need to Print Museum Art at Poster Size
Pixels divided by dpi gives you inches. Here's the table for A4 to A1 and US poster sizes, and when 150 dpi is plenty.
Quick answers
- How many pixels do I need for an A2 poster?
- About 4961 × 7016 pixels at 300 dpi, or 2480 × 3508 at 150 dpi. Posters are usually seen from a metre or more away, so 150 to 200 dpi often looks fine.
- How do I work out print size from pixels?
- Divide the pixel width and height by the print resolution in dpi to get inches, then multiply by 2.54 for centimetres. A 6000 × 8000 pixel file at 300 dpi prints at 20 × 26.7 inches, about 51 × 68 cm.
- Should I upscale a museum image to print bigger?
- Upscaling adds pixels but not detail. It can smooth out a modest enlargement, but check the full file first: museums often serve much larger files than the preview on their page.
The maths is one line: pixels ÷ dpi = inches. Multiply by 2.54 for centimetres. Everything else is deciding what dpi you need.
300 dpi or 150?
- 300 dpi is the usual target for things held in the hand or looked at closely: small prints, cards, book pages.
- 150 to 200 dpi is usually fine for posters and wall prints. People stand a metre or more away. Printers and print-on-demand services often accept this for large sizes. Check what yours asks for.
The table
| Print size | Pixels at 300 dpi | Pixels at 150 dpi |
|---|---|---|
| A4 (21 × 29.7 cm) | 2480 × 3508 | 1240 × 1754 |
| A3 (29.7 × 42 cm) | 3508 × 4961 | 1754 × 2480 |
| 18 × 24 in (46 × 61 cm) | 5400 × 7200 | 2700 × 3600 |
| A2 (42 × 59.4 cm) | 4961 × 7016 | 2480 × 3508 |
| A1 (59.4 × 84.1 cm) | 7016 × 9933 | 3508 × 4967 |
| 24 × 36 in (61 × 91 cm) | 7200 × 10800 | 3600 × 5400 |
Your file won't match these shapes exactly. Paintings aren't A-series rectangles. You'll crop or add a border, so check the short side against the table.
Where the big file is
The image you see on a museum's page is usually a preview. The full file is often much bigger:
- The Met: the download link on open access object pages gives you the original file.
- Rijksmuseum: the download option on the object page, and the full-size image from its image server.
- Smithsonian: the download option on collections.si.edu. Many images also come through its IIIF image server at full size.
Every Musist work page lists the full file's pixel size when the museum states it, with a print-size estimate at 300 dpi, and links straight to the museum's file.
Why some files are small
Older digitisation, a work photographed for a catalogue rather than for print, or a tiny original like a stamp or netsuke. If the full file is 1500 pixels wide, it's a postcard, not a poster. Why Museum Images Look Low-Resolution goes into this.
About upscaling
Upscaling tools add pixels, not detail. They can make a modest enlargement look smoother, and they work better on flat graphics like posters and patterns than on fine engraving. Do a test print at full size before you order a run.
Quick checklist
- Find the full file, not the preview.
- Divide the pixel size by 150 and by 300 to get your range in inches.
- Check the short side against the size you want.
- Crop to the print's shape before upscaling.
- Test print one before ordering many.
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