Guides ·
What DPI do you need for printing?
What to use for photos, posters and banners, why the number depends on viewing distance, and why an image tagged 300 DPI can still print blurry.
300 DPI for anything held in the hand, and 150 DPI for large prints viewed from a few feet away. But DPI is not a property of your image in any meaningful sense: what decides print quality is the pixel dimensions divided by the size you are printing at.
What you actually need
| Printing at | DPI needed | Pixels required |
|---|---|---|
| Passport photo, 35 × 45 mm | 300–600 | 413 × 531 minimum |
| 6 × 4 inch photo | 300 | 1800 × 1200 |
| A4 page, full bleed | 300 | 3508 × 2480 |
| A3 poster | 200–300 | 3508 × 4961 at 300 |
| A1 poster, viewed from 1 m | 150 | 3508 × 4961 |
| Exhibition banner, viewed from 3 m | 72–100 | 2835 × 8504 for a 2 m drop at 100 |
| Anything on a screen | Irrelevant | Match the display size in pixels |
The pattern in that table is the whole subject: the further away it is viewed, the less resolution you need. A billboard is often printed at 15 DPI and looks perfect from the road.
Why DPI on its own means nothing
A DPI value stored in an image file is a note saying “print me at this density”. It changes no pixels and adds no detail. You can set a 500 × 500 image to 300 DPI and it will still print as a 1.67-inch square — badly, if you asked for a poster.
The equation that matters:
printed size (inches) = pixel dimensions ÷ DPI
So a 3000-pixel-wide image prints at 10 inches wide at 300 DPI, or 20 inches at 150. Rearranged, this is how to check whether a photo is good enough for a print you want:
DPI you will get = pixels ÷ inches you want
A 4000-pixel-wide phone photo printed at A3 (16.5 inches wide) gives 242 DPI. Slightly under 300, and in practice indistinguishable.
When the DPI value does matter
Three cases, all of them about other software reading the number rather than about quality:
Print shops and submission systems. Many reject files whose stored DPI is below 300 without examining the pixel dimensions at all. The file may be perfectly adequate; it is the metadata being checked. Setting the DPI field fixes this without changing a single pixel.
Passport and visa applications. These specify a physical size in millimetres and a resolution, and the automated checks read both.
Page layout software. InDesign and Word place an image at its stored DPI by default. A photo tagged 72 DPI arrives four times too large on the page.
The upscaling question
If you do not have enough pixels, you cannot honestly get them. Enlarging invents detail that was never captured — modern tools do this convincingly, but they are guessing.
Better in order: find the original file rather than a copy from a messaging app; reshoot if you can; print smaller; or accept a lower DPI and view it from further away. A slightly soft print at 180 DPI usually looks better than an aggressively upscaled one at 300.
Common questions
Is DPI the same as PPI? In practice, yes, and everyone uses them interchangeably. Strictly, PPI is pixels in an image and DPI is dots a printer lays down — printers use several dots per pixel.
Does changing DPI change image quality? No. It changes only the note about intended print size. The pixels are untouched.
Why does my 300 DPI image print blurry? Because the DPI tag says 300 but the pixel dimensions are too small for the size you printed. Divide pixels by printed inches to see the real figure.
Is 72 DPI a real standard for the web? No, and it never was for modern displays. Screens work in pixels; the DPI value is ignored by every browser.
Can I set DPI without re-compressing the photo? Yes. It lives in the file header. Writing it does not touch the image data, so there is no quality loss and no re-encoding.