Print Size & DPI Calculator

Will your image print sharply?

A photo that looks crisp on screen can print blurry or blocky if it doesn’t have enough pixels for the size you want. The relationship is simple — pixels ÷ resolution = print size — but converting between pixels, inches, centimetres and DPI by hand is tedious. This calculator handles all three questions people usually ask: how big can I print this image, how many pixels do I need for this print, and how sharp will this image be at this size?

How to use the calculator

1. Choose what you want to calculate using the buttons at the top.
2. Enter the image’s width and height in pixels — or drop in the image to read them automatically.
3. Enter the print size, or choose a common size such as 4 × 6 in, A4 or US Letter.
4. Set the resolution, or tap a common value like 150 or 300 DPI.
5. Read the result, including a quality rating when you check an image’s effective DPI.

Images you drop in are only read for their dimensions and never leave your device.

The formulas

• Print size = pixels ÷ DPI. A 3000-pixel-wide image at 300 DPI prints 10 inches wide.
• Pixels needed = print size in inches × DPI. An 8 × 10 in print at 300 DPI needs 2400 × 3000 pixels.
• Effective DPI = pixels ÷ print size in inches. A 2000-pixel image printed 10 inches wide has 200 DPI.

One inch is exactly 2.54 cm or 25.4 mm, so metric sizes are converted to inches before calculating. If an image and a print have different shapes, the calculator uses the lower of the two directions, because that’s the side that limits sharpness — and warns you that the print will need cropping or borders.

What resolution do you need?

• 300 DPI — the standard for photo prints, brochures, books and anything viewed at arm’s length.
• 200–240 DPI — still sharp for most photo prints; many printers can’t show the difference from 300.
• 150 DPI — fine for posters and large prints viewed from a metre or more away.
• Under 100 DPI — pixelation is likely unless the print is viewed from far away, like a banner.

Viewing distance matters as much as the number: the further away people stand, the fewer pixels per inch they can see. That’s why billboards look fine at resolutions that would be unacceptable in a magazine.

DPI versus PPI

Strictly speaking, PPI (pixels per inch) describes images and DPI (dots per inch) describes printers, which use several ink dots to reproduce each pixel. In everyday use the terms are interchangeable, and the value you set when preparing an image is pixels per inch. Changing the DPI setting in an editor without resampling doesn’t add detail — it only changes the default print size.

Cropping for a specific frame? Check proportions with the Aspect Ratio Calculator. Need a printable document from photos? Use JPG to PDF, or make ID photos at the right size with the passport photo tool.