What the DPI Calculator does
This DPI calculator tells you how large you can print an image at 300 DPI or any resolution you choose, how many pixels a print size needs, and what resolution your photo would actually get on A4, A3, US Letter, a 4 x 6 photo or a poster. Type the width and height in pixels - or drop the photo and the page reads them - and every answer updates together.
The image never leaves your browser: it is opened in the tab only to read its size. The page also explains the DPI number stored inside many files, which is only a label and does not change how big the picture can be printed.
How to use it
- Drop a photo onto the box, choose one, or type its width and height in pixels. A phone camera is usually around 4000 x 3000; a Full HD screenshot is 1920 x 1080.
- Set the print resolution. 300 DPI is the usual target for photos and print shops; 150-200 is fine for posters and banners seen from a distance.
- Choose a paper size, or Custom to type any size in centimetres, millimetres or inches. The paper is turned to match the photo's orientation automatically.
- Read the largest print size at your DPI, the DPI you would get on the chosen paper, and the pixels that paper needs. The table rates every standard size at once; copy or download it as CSV.
Reading the results
Pixels are fixed; DPI is a choice. The same 4000 x 3000 image is 13.3 x 10 inches at 300 DPI, 20 x 15 inches at 200 DPI and 55.6 x 41.7 inches at 72 DPI. Nothing about the file changes - only how densely the pixels are laid on paper.
The quality bands are print-trade conventions, not a standard: 300 DPI and above looks sharp even close up; 200 is very good at reading distance; 150 suits posters viewed from an arm's length; below 100 the picture looks soft unless it is seen from across a room.
"Fill" means edge to edge, which crops the photo when its shape differs from the paper's - a 4:3 phone photo on A4 loses about 6% of its long side. The DPI shown is for filling the page; printing the whole image with borders gives a slightly higher figure, given in the note.
Worked example: a 12-megapixel phone photo on A4
A phone photo of 4032 x 3024 pixels at 300 DPI prints up to 4032 / 300 = 13.44 by 3024 / 300 = 10.08 inches, which is 34.1 x 25.6 cm - bigger than A4.
On A4 (297 x 210 mm, turned landscape = 11.69 x 8.27 in), filling the page needs 4032 / 11.69 = 345 DPI across and 3024 / 8.27 = 366 DPI down. The lower figure, 345 DPI, is what you get edge to edge: excellent. A4 at 300 DPI needs 3508 x 2480 pixels, so this photo has room to spare.
Formulas and scoring rules
- Print size
inches = pixels / DPI; cm = inches x 2.541 inch is exactly 25.4 mm.- Pixels needed
pixels = print size in inches x DPIRounded to the nearest pixel, so A4 at 300 DPI is 2480 x 3508 (210 / 25.4 x 300 = 2480.3; 297 / 25.4 x 300 = 3507.9).- Effective DPI on a paper size
fill DPI = min(width px / paper width in, height px / paper height in)Fit (whole image, with borders) uses the larger of the two instead.- What the eye can resolve
ppi = 1 / (distance in inches x tan(1/60 degree)), about 3438 / distance in inchesBased on the 1-arcminute acuity of 20/20 vision: about 175 ppi at 50 cm and 344 ppi at 10 inches.
Limitations: what the result does not prove
- DPI only measures resolution. It says nothing about focus, noise, compression artefacts or colour, all of which affect how a print looks.
- The page reads the size of formats your browser can open (JPEG, PNG, WebP, GIF and usually AVIF). HEIC and camera RAW files must be converted first; nothing is uploaded to do it.
- Printers' own dpi figures (such as 1200 or 4800 dpi) describe ink dots, not image pixels, and are not what you enter here. Print shops quote image resolution, which is what this tool uses.
- Upscaling software can raise the pixel count, but it invents detail rather than recovering it; the quality band then describes the enlarged file, not the original photograph.
Privacy: where your data goes
Everything you paste, type or drop is processed in this browser tab. It is not uploaded, logged, stored or sent to analytics. Session recording and tag-manager scripts are switched off on this page.
Standards and sources
- ISO 216 - Writing paper and certain classes of printed matter - Trimmed sizes - A and B series
- PNG Specification (W3C) - pHYs physical pixel dimensions chunk
- NIST SP 811 - Guide for the Use of the International System of Units (inch = 25.4 mm)
Frequently asked questions
What size can I print my photo at 300 DPI?
Divide each pixel dimension by 300 to get inches. A 4000 x 3000 image prints at 13.3 x 10 inches (33.9 x 25.4 cm). Enter your image size, or drop the photo, and the largest print appears at once.
How many pixels do I need for an A4 print at 300 DPI?
2480 x 3508 pixels, about 8.7 megapixels. A3 needs 3508 x 4961, and a 4 x 6 inch photo 1200 x 1800. Choose any paper size to see the figure for your chosen resolution.
Does changing the DPI in an image file make it better quality?
No. The DPI stored in a JPEG or PNG is only a note saying how large to print it; changing it without resampling leaves every pixel the same. Quality depends on how many pixels you have for the size you print.
Is 72 DPI good enough for printing?
Rarely. 72 DPI is an old screen convention; printed at 72 DPI an image looks blocky up close. Use it only for very large prints seen from far away, and aim for 150 to 300 DPI for anything you hold in your hand.
What is the difference between DPI and PPI?
Strictly, PPI is pixels per inch of the image and DPI is ink dots per inch from a printer. In everyday use - print shops, photo editors and this tool - DPI means pixels per inch of the print.
Is this a mouse DPI calculator?
No - mouse DPI (counts per inch of hand movement) is a different measurement used for game sensitivity. This page is about image resolution and print size; for a mouse, sensitivity x DPI gives the eDPI that gamers compare.
Is my photo uploaded when I drop it on the page?
No. The browser opens it in this tab to read the width, height and any stored DPI value, and nothing is sent anywhere. You can disconnect from the internet and the page still works.
Last reviewed by the A2Z.Tools team against the sources listed above.
