DPI Calculator

How to use

1. 1Pick a mode: Solve for DPI, Solve for pixels, or Solve for print size. The form shows only the inputs you need.
2. 2Type the image pixel dimensions, the print size, or the target DPI in the visible fields, or click a preset chip to fill them in instantly.
3. 3Switch the print-size unit between inches, centimetres, and millimetres; typed values convert automatically so you keep your numbers.
4. 4Read the headline result on the right (effective DPI, pixels needed, or maximum print size) and check the print-quality badge for the band it falls into.
5. 5Open the quality bands list to see which thresholds your DPI passes, copy any single value with the Copy buttons, or use Copy summary for the full breakdown.

About this tool

DPI Calculator solves the relationship between image pixels, physical print size, and resolution. Pick a mode and the tool fills in the missing piece: Solve for DPI returns the effective dots per inch when a given pixel image is printed at a given size, Solve for pixels returns the minimum image dimensions needed to hit a target DPI on a given print, and Solve for print size returns the largest print you can make from a given image at a given target DPI. Print size accepts inches, centimetres, or millimetres, and a unit switch automatically converts your typed values so you do not have to retype them. Both width and height are computed independently because the effective print quality is limited by the lower-density dimension when the image and print aspect ratios do not match; the tool flags the mismatch and reports the lower value as the effective DPI. The result is graded against industry-standard quality bands (72 DPI web, 150 DPI acceptable, 200 DPI good, 300 DPI photo, 600 DPI fine art) so you can quickly tell whether a phone snap will print sharply at 8 by 10 inches, whether a 24 megapixel raw is overkill for a 4 by 6 photo, and how big a poster you can pull from any source image. Quick-pick presets cover the most common consumer print sizes (4 by 6, 5 by 7, 8 by 10, 11 by 14, 16 by 20, 18 by 24, 20 by 30 inch wall prints, US Letter, A3, A4, A5, business cards, and 8 and 12 inch squares for Instagram and album-cover prints), as well as common camera and screen pixel dimensions (Full HD, 4K UHD, 24 MP DSLR, 45 MP camera, iPhone main camera, phone wallpaper). Useful for photographers planning a lab order, designers setting up flyers and posters, scrapbookers and Etsy sellers verifying print resolution, students answering image resolution homework, and anyone who has ever wondered why a low-res image looked great on screen but pixelated on paper. Everything runs locally in your browser; no image is ever uploaded because the tool plans the relationship between pixels, inches, and DPI as numbers.

Free to use. Works in your browser. No signup, no login.