DPI & Print Size Calculator Widget

Help readers know how big they can print a photo, or how many pixels a print job needs. Enter the image's pixel dimensions and a DPI to get the print size in inches or centimetres, with the maximum size at photo, inkjet and poster quality.

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<iframe src="https://a2z.tools/embed/w/dpi-calculator" title="DPI &amp; Print Size Calculator by A2Z Tools" width="100%" height="760" style="border:0;width:100%" loading="lazy" allow="clipboard-write"></iframe>

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How it works

Print size is simply pixels divided by dots (pixels) per inch: a 6000 x 4000 pixel photo printed at 300 DPI measures 20 x 13.33 inches, or 50.8 x 33.87 cm, because one inch is exactly 2.54 cm. The table then repeats the sum at three common quality levels - 300 DPI for photo prints viewed in the hand, 240 DPI for good inkjet output, and 150 DPI for posters and banners seen from a metre or more away - so a reader can see that the same file makes a 40-inch poster at 150 DPI. Switch to the second mode to work backwards: a 20 x 25 cm print at 300 DPI needs 2,363 x 2,953 pixels (rounded up, since a printer cannot use part of a pixel). The swap buttons flip width and height for portrait or landscape. The note explains the common confusion: editing the DPI tag in an image file changes the stated print size but adds no detail.

Method

  • Print size (in) = pixels / DPI; cm = in x 2.54
  • Pixels needed = ceiling(print size in inches x DPI)
  • Megapixels = width px x height px / 1,000,000

Worked examples

24-megapixel camera file

Inputs: 6000 x 4000 px at 300 DPI

Result: 20 x 13.33 in (50.8 x 33.87 cm); 40 x 26.67 in at 150 DPI

6000 / 300 = 20 in; 20 x 2.54 = 50.8 cm.

Pixels for a 20 x 25 cm print

Inputs: 20 x 25 cm at 300 DPI

Result: 2,363 x 2,953 px

20 / 2.54 x 300 = 2,362.2, rounded up to 2,363.

Limitations

  • Does not judge image quality: noise, blur and heavy compression show in a print whatever the DPI.
  • Bleed and margins that a printer adds are not included.
  • Viewing-distance advice is a rule of thumb, not a standard.

Where publishers use it

  • Photo labs and print shops telling customers whether a phone photo can make an A3 print
  • Print-on-demand and merch stores setting minimum artwork sizes for posters and T-shirts
  • Photography courses explaining resolution versus print size
  • Wedding photographers' FAQ pages on how large the delivered files can be printed
  • Self-publishing guides checking cover images against a printer's 300 DPI requirement

Questions

What DPI do I need for printing?

300 DPI is the usual target for photos and brochures viewed at reading distance; 240 DPI looks almost as good on inkjet printers; 150 DPI is fine for posters viewed from a metre or two; large banners seen from across a street can go below 100 DPI.

How big can I print a 12-megapixel photo?

A 4000 x 3000 pixel image prints at 13.3 x 10 inches (33.9 x 25.4 cm) at 300 DPI, 16.7 x 12.5 inches at 240 DPI and 26.7 x 20 inches at 150 DPI.

Does changing the DPI in Photoshop make my image better?

No. Changing the DPI value without resampling only changes the print size the file claims. Detail comes from the pixel count; upscaling invents pixels and can look soft.

Is DPI the same as PPI?

Strictly, PPI is pixels per inch in the image and DPI is ink dots per inch from the printer, but print shops and software use DPI for both. This widget means pixels per inch of the printed image.

How many pixels does an A4 print need?

A4 is 21 x 29.7 cm. At 300 DPI that is 2,481 x 3,508 pixels; at 150 DPI, 1,241 x 1,754 pixels.

Cite or recommend this tool

If you reference this tool in an article, course or documentation, these formats are ready to copy. They are optional - nothing is added to your site unless you paste it.

A2Z Tools DPI & Print Size Calculator
https://a2z.tools/embed/dpi-calculator

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