DPI to Pixels: Formula, Print Size Charts, and Real Examples

Quick answer: DPI to pixels formula

To convert DPI to pixels, multiply the physical print size by the print resolution:

pixels = inches x DPI
pixels = millimeters / 25.4 x DPI
inches = pixels / DPI
DPI = pixels / inches

A 4x6 inch photo at 300 DPI needs 1200x1800 pixels. A 2x2 inch passport photo at 300 DPI needs 600x600 pixels. A4 paper at 300 DPI is about 2480x3508 pixels.

The important catch: DPI alone is not a pixel count. "300 DPI" means 300 pixels for every inch of final print size. You still need the inches, centimeters, or millimeters.

So if someone asks for "a 300 DPI image," ask the missing question: 300 DPI at what physical size?

DPI vs PPI: the term people search and the term printers mean

For digital image files, PPI is the more precise term because the file is made of pixels. A 3000x2000 image has 3000 pixels across and 2000 pixels down. If you print it 10 inches wide, the print density is 300 pixels per inch.

DPI originally describes printer dots per inch: how many ink dots or output marks a printer can lay down. In everyday upload forms, print labs, passport photo instructions, and client emails, people often say "DPI" when they mean "pixels per inch."

This guide uses DPI because that is the search language, but the math you need is really PPI:

image pixels / physical inches = pixels per inch

When a print lab says "300 DPI," read it as "give us enough pixels to print this size sharply."

The mistake: changing the DPI tag is not the same as resizing

Image editors often show three numbers together:

• Width in pixels.
• Height in pixels.
• Resolution, such as 72, 96, 240, or 300 PPI.

Only the first two are actual image detail. The resolution field is a print instruction. If you change a 3000x2000 image from 72 DPI to 300 DPI without resampling, it is still a 3000x2000 image. It will not become sharper, smaller, or more detailed. It will only have a different suggested print size.

Here is the same 3000x2000 image interpreted three ways:

Nothing about the pixels changed. The print label changed.

If your goal is a sharper print, you need enough real pixels for the final print size. If your goal is web display, the DPI tag is usually irrelevant; the browser uses pixel dimensions and CSS layout.

Image DPI explained covers that screen-vs-print confusion in more depth.

DPI to pixels chart for common inch sizes

Use this chart when you know the print size in inches.

For normal close-viewed photo prints, the 300 DPI column is the one people usually want. Adobe's print-resolution guidance describes 300 pixels per inch as the common high-quality print standard, especially for prints viewed up close.

Use 600 DPI only when the job asks for it or when you are dealing with line art, small text, scans, or very fine detail. For a normal phone photo, 600 DPI often creates a large target without adding visible benefit.

DPI to pixels chart for A4, metric, and passport sizes

For metric sizes, divide millimeters by 25.4 to get inches, then multiply by DPI. NIST's conversion guidance defines the international foot from the meter, which gives the familiar exact relationship of 1 inch = 25.4 mm.

Small rounding differences are normal because paper sizes in millimeters rarely convert to a perfect whole number of pixels. Round to the nearest whole pixel unless a specific upload system says otherwise.

Reverse chart: pixels to print size

If you already have an image and want to know how large it can print, divide the pixels by the target DPI.

This table is often more useful than a DPI-to-pixels chart because real life starts with a file you already have. If your phone photo is 4000x3000 pixels, it can make a sharp 13.3x10 inch print at 300 DPI. It can make a larger print at 150 DPI, especially if people view it from farther away.

Worked examples

Example 1: 4x6 photo at 300 DPI

width: 4 x 300 = 1200 pixels
height: 6 x 300 = 1800 pixels
answer: 1200x1800 pixels

This is the standard size for a small photo print. If your file is 1800x1200 instead, that is the same shape in landscape orientation.

Example 2: 8x10 print from a 4000x3000 file

At 300 DPI, an 8x10 print needs 2400x3000 pixels. A 4000x3000 file has enough height but too much width for the 8x10 aspect ratio. You will need to crop from 4:3 to 5:4, then export around 2400x3000 or larger.

This is where people get confused: the file has enough pixels, but the shape is not the same as the print.

Example 3: A4 at 300 DPI

A4 is 210x297 mm.

210 / 25.4 x 300 = 2480 pixels
297 / 25.4 x 300 = 3508 pixels
answer: 2480x3508 pixels

This is the common pixel size for an A4 page image at 300 DPI.

Example 4: 35x45 mm ID photo at 300 DPI

35 / 25.4 x 300 = 413 pixels
45 / 25.4 x 300 = 531 pixels
answer: 413x531 pixels

For passport or visa photos, do not stop at the outer pixel size. Many countries also define head height, eye position, background, expression, and print-paper rules.

Aspect ratio matters as much as DPI

DPI math tells you how many pixels are needed. It does not tell you whether your photo has the right shape.

Compare these common ratios:

If the image has enough pixels but the wrong shape, resizing alone will stretch the image. Crop first, then resize. Stretching a face, product, document, or logo to force a target size is the fastest way to make a print look wrong.

Which DPI should you use?

Use DPI based on output, not habit.

Do not upscale a small file to hit a chart number unless the upload system refuses anything else. Upscaling can satisfy a pixel-count rule, but it cannot recreate detail that was never captured.

Why 72 DPI and 96 DPI confuse web images

The 72 DPI number is a historical screen convention. The 96 DPI number appears in CSS because web layout uses a reference pixel model. The W3C CSS guidance says CSS is best thought of by output medium: pixels are natural for screens, while physical units such as inches and centimeters are for print. MDN's CSS resolution docs also note that 1dppx equals 96dpi because CSS has a fixed 1:96 relationship between CSS inches and CSS pixels.

That does not mean your image must be exported at 96 DPI for the web.

For websites, the questions are:

• How many image pixels does the layout need?
• Is the file being displayed on high-density screens?
• Is the file compressed well?
• Is the format appropriate, such as JPG, PNG, WebP, or AVIF?

A 1200x800 image tagged 72 DPI and the same 1200x800 image tagged 300 DPI render the same in a browser. If you want the web version to look better, change the pixel dimensions, compression, or source quality, not the DPI tag.

How to resize to a DPI-derived pixel target in PhotoTools

PhotoTools does not need to change the DPI metadata tag to make a print-ready copy. It changes the actual pixel dimensions, which is the part that matters for image detail.

Use this workflow:

1. Decide the physical print size, such as 4x6 inches or A4.
2. Choose the target DPI, usually 300 for close-viewed prints.
3. Calculate the pixel size from the chart or formula.
4. Open Resize Images.
5. Switch to exact dimensions.
6. Enter the target width and height in pixels.
7. Keep the aspect-ratio lock on if you are setting only one side.
8. If the image must match an exact shape, crop first, then resize.
9. Choose the output format: JPG for photos, PNG for graphics or transparency, WebP for modern web use.
10. Download the resized copy and keep your original file.

For batches, resize one sample first and check it at the intended print size. Then process the rest. PhotoTools runs the resize in your browser and supports batch downloads, so you do not have to upload personal photos to a server just to change pixel dimensions.

What to do when a form says "300 DPI"

Upload forms often use "300 DPI" as shorthand for "high enough resolution." They may not actually inspect the DPI metadata tag. Some check only pixel dimensions and file size.

Use this triage:

• If the form gives a physical size and DPI, calculate pixels.
• If the form gives only pixel dimensions, follow the pixel dimensions.
• If the form gives only "300 DPI," look for a hidden size requirement in inches, cm, or mm.
• If a print shop rejects the file for DPI metadata after the pixels are correct, export from a print editor that can set the metadata tag.
• If a website asks for 72 DPI, treat that as outdated wording and look for pixel dimensions instead.

For passport, visa, school, medical, and government submissions, check the official instructions first. Pixel size is only one rule; cropping, background, file type, file size, paper type, and image editing restrictions can matter too.

Technical sources checked

This guide was reviewed against:

• W3C CSS units guidance, especially the difference between screen and print units.
• CSS Values and Units Module Level 4, for the CSS reference pixel and 96 DPI context.
• MDN CSS resolution documentation, for dpi, dpcm, and dppx definitions.
• Adobe Photoshop print-resolution guidance, for the practical 300 PPI print standard and viewing-distance caveat.
• NIST SI conversion factors, for inch-to-meter relationships behind the 25.4 mm per inch conversion.

Bottom line: use DPI to calculate the pixel target for print, but use actual pixel dimensions to judge image detail.