The usual advice is that print images should be 300dpi. That is right, but incomplete in a way that causes real problems: 300dpi only means anything in relation to the size the image is printed at.
Effective resolution is what counts
An image's resolution changes as you scale it in the layout. Place a 300dpi image and enlarge it to 200%, and you now have a 150dpi image — the same pixels spread over twice the area. Shrink it to 50% and it becomes 600dpi.
This is why our requirement is 300dpi *effective at final size*. Not the number in the file's properties, the number after your layout scales it.
Working it out
Pixel dimensions divided by print size in inches gives effective resolution. To go the other way: multiply the printed size in inches by 300 to get the pixels you need.
- A full-bleed A5 flyer (148 × 210mm, about 5.8 × 8.3in) needs roughly 1,750 × 2,480 pixels.
- A full-bleed A4 (8.3 × 11.7in) needs roughly 2,480 × 3,510 pixels.
- A 90 × 55mm business card needs roughly 1,060 × 650 pixels.
Add bleed on top of each of those. Most design software shows effective resolution in a links or info panel — that is the number to check, not the one in the original file.
Where low-resolution images come from
- Images saved from a website. Screen images are typically 72dpi and sized for a screen.
- Logos supplied as a small PNG or JPEG rather than a vector file.
- Screenshots, which are always screen resolution by definition.
- Photos sent through a messaging app, which compresses and downscales them.
Always ask for the original file rather than working with what came through email or a chat.
Logos are a special case
A logo should be vector — AI, EPS or a vector PDF — not a raster image. Vector artwork has no resolution at all; it is drawn from maths and stays sharp at any size. If you only have a raster logo, get the vector version from whoever designed it before printing anything where the logo is large.
What happens if it is too low
Soft edges, visible squares in flat areas, and mushy text inside images. At mild shortfalls it just looks slightly out of focus; the customer may not name it but will register it.
Our file check scans image resolution across the document and tells you before you pay. A warning is advice rather than a block — you can acknowledge it and we will print. On a photograph it is often fine; on a logo it never is.