Poster print size calculator
A poster is the one print where the question cannot be settled by resolution alone. The same 96 DPI that ruins a business card is unremarkable on a wall seen from three metres. This works the three variables together: the pixels you have, the size you want, and the distance the poster will actually be read from.
Enter the pixel dimensions of your file to work the poster size against them.
| Third variable | Viewing distance sits beside pixels and poster size, not after them |
|---|---|
| You provide | Source pixels, the poster width and height, and how far back it hangs |
| You get | Effective DPI, the pixel budget that size asks for, and a distance reference |
| Pixel budget | The shortfall or the surplus written out in pixels, not as a pass or a failure |
| Distance assumption | One arcminute of resolving power, printed on the page instead of buried in the code |
| Runs | Arithmetic performed in your browser — no upload, no account, no cookie |
What the viewing-distance figure can and cannot tell you
One stated assumption drives that readout: normal 20/20 vision separates detail subtending roughly one arcminute, so the tool reports the resolution at which a single pixel of your poster spans exactly that angle at the distance you typed. Treat it as a marker on the scale rather than a line your file crosses. It is arithmetic on one assumption, and here is what that assumption does not know:
- Individual eyesight varies — 20/20 is a definition, not a ceiling
- High-contrast edges such as black type stay legible well past the marker
- Every press loses some of the detail the file carried before the sheet dries
- Nobody looks at a poster from one fixed distance for its whole life
The shortfall is reported in pixels, not adjectives
"Too low" tells you nothing you can act on. The budget row states what the size you asked for wants at 300 DPI, states what your file carries, and subtracts. Being 3,200 pixels short is a fact you can take to the person who owns the original artwork; being short by a factor of 0.56 is the same fact in the shape a quote is written in.
The shorter edge sets the answer
Resolution is measured on both axes because a file rarely matches the proportions of the frame it is going into. Stretch a 6000 × 1200 image across a 20 × 20 inch poster and the horizontal lands on 300 while the vertical falls to 60. Averaging those, or quoting only the flattering one, produces a number that is arithmetically true and practically useless, so the tighter axis is the one the rest of the page is built on.
Reading the size ladder underneath
The last table ignores the poster size you typed and asks the opposite question: at 300, 200 and 150 DPI, how large does this specific file go before it starts inventing detail? It is the sanity check for when the requested size turns out to be optimistic — the row you can reach tells you which conversation to have with the printer, and which one to have with whoever supplied the file.
FAQ
- Why does the reference land near 286 DPI at reading distance?
- Because that is what one arcminute works out to at twelve inches. It sits close enough to the familiar 300 DPI target that the two are usually treated as the same working number, which is a useful way to see that the habit and the geometry agree rather than compete.
- Can I print a poster below the distance reference?
- People do it constantly, and the calculator will not stop you. What it refuses to do is tell you the result will be fine, because that depends on your artwork, your press and your viewer — none of which this page can measure. It reports the numbers and leaves the call where it belongs.
- What distance should I enter for a poster I have not hung yet?
- Pick the closest place someone will realistically stand, not the average. A hallway piece gets read from an arm's length away even when it was designed to be seen from the far end, and the closest look is the one that finds the softness.
- Does upscaling the file change the pixel budget?
- It changes the count and not the detail. Resampling raises the numbers this page reads, so the budget row will report the gap as closed while the print stays exactly as soft as it was. The honest fix is a larger original, a vector version, or a smaller poster.
- Why is the poster width and height asked for separately?
- Because posters are ordered in fixed formats — 18 × 24, 24 × 36, A2, B1 — and those formats rarely share the proportions of a camera sensor or a design canvas. Entering both edges shows you where the mismatch falls before it becomes a cropping decision at the printer.