How DPI converts pixels to print size
An image has no physical size until it is printed. DPI decides how many of its pixels fit into each inch of paper. The formula is:
print size (in) = pixels ÷ DPI
pixels needed = print size (in) × DPI
So 3,000 pixels at 300 DPI prints 10 inches wide. Print the same file at 150 DPI and it covers 20 inches, but each inch carries half the detail. The pixels never change; only how thinly they are spread.
How much resolution is enough?
The quality check in this calculator uses these bands. They are rules of thumb; viewing distance matters as much as the number.
| Effective DPI | What to expect |
|---|---|
| 300 DPI and above | Print-ready. Sharp at normal reading distance: books, brochures, photo prints. |
| 200 to 299 DPI | Good. Fine for most photos and marketing prints. |
| 150 to 199 DPI | Acceptable for large prints viewed from a distance, such as posters. |
| Below 150 DPI | Low. Likely to look soft or pixelated up close. |
Changing a file's shape as well as its size? Work out the ratio first with the Aspect Ratio Calculator.
Frequently asked questions
What is the difference between DPI and PPI?
PPI (pixels per inch) describes a digital image: how many pixels are packed into each inch when it is printed. DPI (dots per inch) strictly describes a printer: how many ink dots it lays down. In everyday use, including in Photoshop and most print specs, "300 DPI" means 300 pixels per inch, and that is how this calculator uses it.
How do I convert pixels to inches?
Divide the pixel dimension by the DPI. A 3,000-pixel-wide image printed at 300 DPI is 3,000 ÷ 300 = 10 inches wide. To get centimeters, multiply inches by 2.54.
Does changing the DPI setting make my image sharper?
No. Changing the DPI value in an image file without resampling only changes the print size it reports. The pixel count, and therefore the detail, stays the same. On screen, the DPI value has no effect at all.
What is bleed and why add it?
Bleed is extra image area beyond the trim line, so a slightly off cut does not leave a white edge. A common standard is 0.125 inches (3 mm) on each side. Turn on bleed in the print-size mode to see the pixels you need including it. Always confirm the exact bleed with your printer or platform.
What DPI do I need for a poster?
People view posters from further away, so 150 to 200 DPI is often enough at large sizes. For anything held in the hand, such as a book, flyer or photo print, aim for 300 DPI.