DPI to Pixels Calculator

Free · No upload · Works offline once loaded

Type in a print size and this tells you how many pixels you need. Flip it around and it tells you how big you can print what you already have. Both directions, any DPI.

Everything runs in your browser — the numbers never go anywhere. If you need to actually change a file rather than just work out the maths, the DPI converter rewrites the header value without touching your pixels, and the image resizer handles exact pixel dimensions.

How to convert 300 DPI to pixels

Multiply the physical size in inches by 300. That is the whole calculation — 300 DPI means 300 pixels per inch, so an 8 × 10 inch print at 300 DPI needs 2400 × 3000 pixels.

If your measurement is in millimetres or centimetres, convert to inches first by dividing by 25.4 or 2.54, then multiply by 300. A 35 × 45 mm passport photo is 1.378 × 1.772 inches, which lands at 413 × 531 pixels at 300 DPI.

Going the other way is just as simple: divide pixels by 300 to get the largest size that still prints at full quality. A 3000-pixel-wide file prints cleanly at 10 inches wide, because 3000 ÷ 300 = 10. Push it wider than that and the effective density drops below 300 DPI.

Why 300 specifically? It is the point where the human eye stops resolving individual dots at normal reading distance, so commercial printers, photo labs and passport authorities almost all standardise on it. Below roughly 200 DPI a print starts to look soft; above 300 you are mostly making the file bigger without making it look better, which is why 600 DPI is reserved for archival scanning and fine-art work.

One thing that catches people out: changing the DPI tag on a file does not add pixels. If a portal rejects your image for being under 300 DPI, check whether it wants a different header value — which the 300 DPI converter fixes losslessly — or genuinely more detail, which no tool can invent.

300 DPI to pixels: common print sizes

These are the numbers people ask for most often. All calculated at 300 DPI, the standard for anything that gets printed.

ID and passport photos

A note on the two rows at the top and bottom of that table. US and India passports are officially 2 × 2 inches; 51 × 51 mm is the rounded metric equivalent, and if you run 51 mm through the calculator you get 602 px rather than 600. Use the inch value. Indian exam portals are the opposite case — they state pixel dimensions directly and never mention DPI, so there is nothing to convert.

Photo print sizes

A-series paper

What DPI actually means

DPI stands for dots per inch. It is a printing instruction, not a property of the image itself. The image is a grid of pixels — say 1800 across. The DPI value tells a printer how tightly to pack those pixels onto paper. At 300 DPI, 1800 pixels covers six inches. At 600 DPI the same 1800 pixels covers three inches, printed twice as densely.

Nothing about the picture changed. You did not gain or lose detail. You changed how big it comes out.

This is why “save this at 300 DPI” is, on its own, an incomplete instruction — and why so many people end up confused when they change the DPI and the file looks identical. It should look identical. That is the correct behaviour.

Going the other way: what can I print from what I have?

Flip the calculator to Pixels → print size and it divides instead of multiplies. A 12 megapixel phone photo at 4000 × 3000 px gives you a clean 13.3 × 10 inch print at 300 DPI, or roughly 26 × 20 inches at 150 DPI if it is going on a wall and nobody is inspecting it from six inches away.

If the number comes out smaller than you want, you have two options: accept a lower DPI, or add pixels by upscaling. Upscaling invents detail rather than recovering it, so it works better on graphics and flat colour than on fine texture — but for a moderate 2x enlargement it is usually fine.

Questions

How do I convert 300 DPI to pixels?

Multiply the physical size in inches by 300. A 4 x 6 inch print at 300 DPI is 1200 x 1800 pixels. If your size is in millimetres, divide by 25.4 first to get inches — so a 35 x 45 mm UK passport photo is 1.38 x 1.77 inches, which lands at 413 x 531 pixels.

How many pixels is 600 DPI?

600 DPI on its own is not a pixel count — it is a density. You need a physical size before it means anything. One inch at 600 DPI is 600 pixels; a 4 x 6 inch print at 600 DPI is 2400 x 3600 pixels. This trips people up constantly, which is why the calculator above asks for a size first.

Does changing DPI change image quality?

No, not by itself. DPI is a number stored in the file header saying how large the image should print. Changing it from 72 to 300 does not add a single pixel — the image is identical, it just prints smaller and sharper. Quality only changes when you resample, which means actually adding or removing pixels.

How many pixels is a passport photo?

US and India passports are 51 x 51 mm, which is 600 x 600 pixels at 300 DPI. UK and most EU passports are 35 x 45 mm, which is 413 x 531 pixels at 300 DPI. Nearly every passport authority specifies 300 DPI, so those pixel numbers are what you actually want to submit.

Why does my form want both 300 DPI and specific pixel dimensions?

Because they check two different things. The pixel dimensions decide how much detail is in the file; the DPI tag decides how big it prints. A form that wants 600 x 600 px at 300 DPI is asking for a 2 x 2 inch print at standard print density. You may need the resizer for the pixels and the DPI converter for the header value.

What DPI should I use for printing?

300 DPI is the standard for photo prints and almost anything commercially printed — it is the point where the eye stops resolving individual dots at normal viewing distance. 150 DPI is fine for large posters you view from further away. 600 DPI is for fine-art reproduction and archival scanning, and mostly just makes enormous files otherwise.

Is 3000 px the same as 300 DPI?

No — they measure different things. 3000 pixels is a count; 300 DPI is a density. Put them together and you get a size: 3000 pixels at 300 DPI prints 10 inches wide, because 3000 ÷ 300 = 10. The same 3000-pixel file at 600 DPI prints 5 inches wide. The pixels never changed; only the number in the header did.

How to get 600 DPI resolution?

Two different jobs, depending on what is being asked of you. If a form just wants the file tagged 600 DPI, the 600 DPI converter rewrites the header value losslessly and your pixels are untouched. If it wants genuine 600 DPI detail, you need enough pixels for the physical size first — multiply inches by 600 — and that has to come from the scan or camera, not from changing a tag.

What is a 600 DPI image?

An image whose header says it should print at 600 dots per inch. On its own that tells you nothing about size — one inch at 600 DPI is 600 pixels, while a 4 × 6 inch print at 600 DPI is 2400 × 3600 pixels. 600 DPI is used for fine-art reproduction and archival scanning; 300 DPI is the standard everywhere else.

Related tools

• DPI converter — change the DPI stored in a file, losslessly
• Resize image — set exact pixel dimensions
• Passport photo maker — outputs the ID sizes above at 300 DPI
• Exam photo resizer — exact pixels and an exact KB cap
• Compress image — hit a target file size without wrecking quality