Rasterbator

Print DPI Calculator

Upload an image and pick a paper size — we'll tell you the print DPI and whether it's sharp enough for posters, photos, or large wall art.

Paper size

Check if your image is print-ready

Upload or enter image pixels, pick a print size, and see the resulting DPI.

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Unit
Actual DPI
121
Optical minimum
At 1 m viewing distance, the human eye resolves about 87 DPI. Yours: 121 — easily above the threshold.
Practical recommendation
Industry practice: 300 DPI for professional prints, 150 DPI for home posters.
Acceptable — fine for large wall posters viewed from further back
Image is 1.50:1, paper is 0.71:1 — about 15.7 cm will be cropped or left blank unless you adjust the print size.

Optical minimum comes from the human-eye resolution formula (1 arcminute). Practical recommendations add a safety margin for printer variation and viewing conditions.

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What DPI do I actually need?

DPI requirements depend on how far away the poster will be viewed.

At 1 m viewing: about 87 DPI is the optical minimum.

Halftone posters tolerate even lower DPI — the dot pattern hides pixelation down to 50–75 DPI when viewed from 1.5 m or more. That's why Rasterbator prints look great even with low-resolution sources.

DPI vs PPI — what's the difference?

DPI (dots per inch) describes the density of printer dots on paper. PPI (pixels per inch) describes the density of pixels on a digital image or screen. For print work, the two terms get used interchangeably because what matters is how many pixels from your image land on each printed inch. A screen PPI value on its own says nothing about print quality — only image pixel count and the final print size do. This calculator focuses on print: pixel count ÷ print size in inches = DPI.

Print DPI FAQ

What DPI do I need to print a poster?
For prints viewed up close (books, photo prints, fine art) aim for 300 DPI. For wall posters viewed from 1 metre or more, 150 DPI is plenty. For very large posters viewed from across a room, 75–100 DPI often looks fine — especially with halftone effects.
Is 72 DPI good enough for a wall poster?
For a small photo print, no. For a large wall poster viewed from 2 metres or more, 72 DPI can actually look acceptable — the viewing distance is far enough that the eye can't resolve finer detail. Halftone poster effects make this even more forgiving.
How do I find my image's DPI?
An image file doesn't have a fixed DPI on its own — it has a pixel count (for example 3000 × 2000 pixels). DPI is determined when you choose a print size. A 3000 × 2000 image printed at 10 × 6.67 inches is 300 DPI; printed at 20 × 13.3 inches it's 150 DPI.
Can I increase DPI without losing quality?
Not really. Upscaling invents pixels that weren't there and introduces softness or artifacts. The only reliable ways to increase effective DPI are to print at a smaller physical size, or start with a higher-resolution source image.
Does halftone printing need high DPI?
No. Halftone printing converts continuous tones into a pattern of dots. The dot pattern itself looks intentional at low DPI — pixelation that would be obvious in a regular print is hidden inside the halftone texture. That's why Rasterbator posters can look stunning even from phone-camera source images.
I was looking for screen PPI or mouse DPI — is this the right tool?
Probably not. This calculator is for print DPI — the pixels-per-inch of an image when printed on paper. For monitor PPI (display pixel density) or mouse DPI (cursor sensitivity), look for a tool labeled specifically for those — the concepts share a name but mean different things.

Ready to print your poster?

Take your image into the Rasterbator poster maker — we'll split it across multiple pages and apply a halftone effect tuned for low-DPI sources.

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