Print Size & DPI Calculator
Print size, density and viewing distance — where the 300 DPI standard turns out to be human eyesight at twelve inches, and the real figure is 286.
One arcminute is ordinary eyesight; sharper eyes and deliberately close inspection resolve more, and the figures below scale straight with that. Printing technology matters too — an inkjet dot is not a pixel, and a printer's own "dpi" is a different number from the one here. Nothing is uploaded.
The 300 DPI rule is eyesight at twelve inches — and it is really 286
Normal acuity resolves about one arcminute. At twelve inches that works out at 286.5 DPI, and "300" is that rounded to a memorable number. Which means the standard is not a property of paper or ink at all — it is a property of where you stand, and it is exactly inverse in the distance. A framed print at two feet needs 143; a billboard at fifty feet needs 5.7, some 50 times less.
| Seen from | Distance | Density the eye can resolve |
|---|---|---|
| A book, held | 12 in | 286.5 DPI |
| A framed print | 24 in | 143.2 DPI |
| A large print on a wall | 48 in | 71.6 DPI |
| A poster across a room | 120 in | 28.6 DPI |
| A billboard | 600 in | 5.7 DPI |
Printing a billboard at 300 DPI is not thoroughness — it is a file fifty times larger than any eye will resolve. The requirement halves every time the viewing distance doubles, which is the whole rule and the reason huge prints from ordinary files look perfectly sharp on a wall.
And twice as wide costs four times the pixels, not two
A 20-inch print at 300 DPI and a 40-inch print at 150 come from the same file: halving the density doubles the linear size. But the area quadruples — which is why "twice as big" feels like it should cost twice the resolution and actually costs four times as much paper for the same pixels spread half as densely.
| Density | Print size | Area |
|---|---|---|
| 72 DPI | 83.3 × 55.6 in | 4630 in² |
| 150 DPI | 40.0 × 26.7 in | 1067 in² |
| 240 DPI | 25.0 × 16.7 in | 417 in² |
| 300 DPI | 20.0 × 13.3 in | 267 in² |
| 360 DPI | 16.7 × 11.1 in | 185 in² |
Read the other way round: pick a print width and the density follows, halving each time the width doubles while the area goes up fourfold.
| Print width | Density | Area |
|---|---|---|
| 10 in | 600 DPI | 67 in² |
| 20 in | 300 DPI | 267 in² |
| 40 in | 150 DPI | 1067 in² |
| 80 in | 75 DPI | 4267 in² |
How to use
- Enter your image dimensions in pixels.
- Enter the print density you want to use.
- Enter how far away the print will be seen.
- Read the print size and whether the density is visible.
Frequently asked questions
Where does the 300 DPI rule come from?
Human eyesight. Normal acuity resolves about one arcminute, which at twelve inches works out at 286.5 dots per inch — and 300 is that rounded to a memorable number. It is not a property of paper or ink at all.
Do I always need 300 DPI?
Only for something held at arm length. The requirement is exactly inverse in the viewing distance, so a framed print at two feet needs 143, a poster across a room needs 29, and a billboard at fifty feet needs under six.
How big can I print a 24 megapixel file?
20 by 13.3 inches at 300 DPI, or 40 by 26.7 at 150. Both are the same file — halving the density doubles the linear size, which is why a big print from an ordinary file looks perfectly sharp on a wall.
Does twice as big need twice the pixels?
No, four times. Doubling the linear size halves the density while the AREA quadruples, so the same pixels are spread over four times the paper. That mismatch is what makes upscaling feel worse than expected.
What if my eyesight is sharper than average?
The figures scale straight with it. Half an arcminute asks for twice the density, so a deliberately close inspection of a print needs roughly double what the standard suggests — which is what pixel-peepers are really measuring.
Is a printer DPI the same as this one?
No, and confusing them is common. An inkjet lays down many tiny dots to make one image pixel, so a printer quoting 1440 dpi is describing its own dots. The number here is image pixels per inch of paper.
Should I upscale before printing?
It cannot add detail that was never captured, but a good upscale can help a printer driver by handing it a file at its preferred density. Whether anyone can see the difference depends entirely on the viewing distance.
Does this send anything anywhere?
No. Every figure is computed in your browser, and nothing is uploaded or stored.
🔒 This tool runs entirely in your browser. Nothing you enter is uploaded, logged, or stored.