DPI vs PPI — the complete guide
What DPI and PPI actually mean, which number to use for screen and for print, and exactly how many pixels you need for every common print size.
DPI and PPI are not the same thing
These two get used interchangeably every day, including by print shops, but they describe different things. PPI (pixels per inch) is a property of a digital image — how many pixels are packed into each inch when it is displayed or printed. DPI (dots per inch) is a property of a printer — how many ink dots the hardware lays down per inch. An image file has PPI. A printer has DPI. When someone asks you for a 300 DPI file, what they actually want is an image at 300 PPI.
| Term | Belongs to | Measures | You control it | Set in the file |
|---|---|---|---|---|
| PPIPixels per inch | The image file | Pixel density of the picture | ||
| DPIDots per inch | The printer | Ink dots the hardware can place |
In everyday use “300 DPI” almost always means “an image prepared at 300 PPI”. This guide follows that convention wherever it would be pedantic not to.
72, 96, 150, 300 or 600 — which one and when
The right number depends entirely on how far away the result will be viewed and whether it is made of light or ink. Here is the short version.
| DPI | Use it for | Screen | Verdict | |
|---|---|---|---|---|
| 72Legacy | Old Mac screens, the PostScript point | Outdated for the web | ||
| 96Web standard | Websites, apps, anything on a display | Correct for screens | ||
| 150Draft | Internal drafts, large banners seen from afar | Acceptable, not final | ||
| 300Print standard | Photos, brochures, anything read up close | The professional minimum | ||
| 600High quality | Fine art, line art, very small type | Overkill for photos |
How many pixels do you need to print?
Multiply the physical size in inches by the DPI. These are the numbers for the sizes people ask about most — at draft, standard and high quality.
| Print size | 150 DPI (draft) | 300 DPI (standard) | 600 DPI (high) |
|---|---|---|---|
| 10 × 15 cm photo10 × 15 cm | 591 × 886 | 1,182 × 1,772 | 2,363 × 3,544 |
| A514.8 × 21 cm | 875 × 1,241 | 1,749 × 2,481 | 3,497 × 4,961 |
| A421 × 29.7 cm | 1,241 × 1,754 | 2,481 × 3,508 | 4,961 × 7,016 |
| Letter21.59 × 27.94 cm | 1,275 × 1,650 | 2,550 × 3,300 | 5,100 × 6,600 |
| A329.7 × 42 cm | 1,754 × 2,481 | 3,508 × 4,961 | 7,016 × 9,922 |
| Poster 50 × 70 cm50 × 70 cm | 2,953 × 4,134 | 5,906 × 8,268 | 11,812 × 16,536 |
Calculated live on this page: pixels = size ÷ 2.54 × DPI, rounded up.
Why the web is 96 DPI, not 72
The 72 figure is a historical accident that refuses to die. Early Macintosh displays were built so that one screen pixel matched one PostScript point, and a point is 1/72 of an inch — so 72 became shorthand for “screen resolution”. Modern displays have nothing to do with that ratio. The CSS specification defines its reference pixel as 1/96 of an inch, which is why browsers, design tools and operating systems all work from 96. If you export web graphics at 72 DPI you are not making them smaller or lighter; the DPI tag is simply metadata that browsers ignore. What matters on screen is the pixel count.
- ✓Browsers ignore the DPI metadata in an image entirely — only the pixel dimensions matter
- ✓Setting 72 instead of 96 changes nothing about file size or sharpness on the web
- ✓The 72 number is still correct for one thing: the typographic point, where 72 pt = 1 inch
What actually happens when the DPI is too low
Nothing breaks — the printer simply has to spread the pixels you gave it across a bigger area, so each one covers more paper. Below roughly 150 PPI you start to see soft edges; below 100 the pixel grid itself becomes visible as blocky steps, most obviously along diagonal lines and around text. Enlarging the file in an editor afterwards does not add detail, because the detail was never captured. The only real fixes are to start from a higher-resolution original, print smaller, or accept the softness because the piece will be viewed from a distance.
- ✓300 PPI and above: sharp at reading distance
- ✓150–300 PPI: acceptable for posters and anything viewed from a metre away
- ✓Below 150 PPI: visibly soft up close, blocky below 100
What is my screen's DPI?
A display's real pixel density is its pixel count divided by its diagonal size, and it varies enormously: a typical 27-inch 1440p monitor sits near 109 PPI, a 15-inch laptop at 1080p near 141, and a modern phone can exceed 400. This is why a photo that fills your phone screen can look tiny on a desktop monitor. It is also why the web standardises on a 96 DPI reference pixel rather than the physical density — the browser scales that reference to whatever the hardware actually has, so layouts stay a consistent physical size across wildly different screens.
Viewing distance changes everything
The 300 PPI rule exists because the human eye resolves roughly 300 distinct points per inch at normal reading distance, about 30–45 cm. Double the viewing distance and you can halve the resolution without anyone noticing. That is why a billboard read from twenty metres can be printed at 15 PPI and still look perfect, while a business card held in the hand needs the full 300. Before you chase a higher number, ask how far away the piece will actually be.
Frequently asked questions
Why is 300 DPI the print standard?
Because that is roughly where the human eye stops resolving individual dots at normal reading distance of about 30–45 cm. Past 300 PPI, most people cannot see any extra detail without a magnifier, so printing higher usually costs file size and processing time for no visible gain.
What happens if my DPI is too low?
The printer spreads your existing pixels over a larger area, so each pixel covers more paper. Edges go soft below about 150 PPI, and below 100 PPI the pixel grid becomes visible as blocky steps, especially on diagonal lines and text. Upscaling in an editor afterwards cannot recover detail that was never there.
What is my screen's DPI?
It is the pixel count divided by the diagonal size, and it varies a lot — around 109 PPI for a 27-inch 1440p monitor, around 141 for a 15-inch 1080p laptop, and over 400 on modern phones. The web deliberately ignores this and uses a fixed 96 DPI reference pixel, which the browser then scales to the real hardware.
Is DPI the same as resolution?
No. Resolution is the total pixel count, such as 3000 × 2000. DPI is how densely those pixels are laid down per inch, which decides the physical size. The same 3000-pixel width is 79 cm at 96 DPI but only 25.4 cm at 300 DPI.
Should I set my images to 72 DPI for the web?
No. The DPI value stored in an image is metadata that browsers ignore completely — only the pixel dimensions affect how a picture appears online. The 72 figure is a leftover from early Macintosh screens; the modern CSS reference is 96.
Can I increase the DPI of an existing image?
You can change the number, but that alone does not add detail. Raising DPI without resampling simply makes the image print smaller; raising it with resampling invents pixels by interpolation, which can look smoother but never recovers real texture. Starting from a higher-resolution original is always better.
Related guides
- Pixel to CM Converter — Convert px to cm, mm, inches and points at any DPI.
- Paper sizes guide — A3, A4, A5, Letter, Legal and Ledger in mm, cm and inches.
- Image formats guide — JPG, PNG, WebP, AVIF and SVG compared.