How to use the DPI calculator
- Pick one of the three modes at the top. "Pixels → inches / cm" tells you how large an image prints, "Inches / cm / mm → pixels" tells you how many pixels a given print size requires, and "Screen PPI" measures the pixel density of a monitor, phone or television.
- Type your values. In pixel mode enter the width and, if you like, the height, then tap 72, 96, 150 or 300 DPI or type your own number. When the height is left empty only the width is calculated.
- The result appears as you type, so there is no calculate button to press. Sizes are shown in inches, centimeters and millimeters together. "Copy result" puts a one-line summary on your clipboard, handy for an email to a print shop or a note in a design brief.
- If you want to know whether a photo is big enough for a print, use the quick answer box. Enter the pixel size and you will see the physical size at 300, 200 and 150 DPI, plus the effective DPI for standard paper sizes such as 4×6, 8×10 and A4.
- If you enter something the page cannot read, an error message explains which field is wrong and how to fix it, for example by removing a unit or replacing a comma used as a decimal mark.
What are pixels, DPI and PPI?
A pixel is the smallest building block of a digital image, a tiny square holding one color. A photo described as 3000 × 2000 pixels has 3000 columns and 2000 rows, six million dots in total, or six megapixels. DPI stands for dots per inch and describes how tightly a printer packs ink dots into one inch of paper. PPI stands for pixels per inch and describes the same idea for images and screens. Print professionals care about the difference, but for converting a pixel count into a physical size the two behave identically, so this page says DPI when talking about paper and PPI when talking about displays.
The most common misunderstanding is that DPI changes the number of pixels in a file. It does not. A 3000 × 2000 image is always six megapixels. DPI only decides how widely those pixels are spread when the image is printed. Pack them tightly and you get a small, crisp print; spread them out and you get a large print that looks softer. The DPI value saved in a file is just a suggested print density, and editing that label with resampling switched off does not touch a single pixel.
The formulas behind the numbers
Everything on this page comes from three short calculations. Divide pixels by DPI to get inches, and multiply inches by 2.54 for centimeters. Go the other way by dividing a length in inches by one and multiplying by DPI. For screens, take the diagonal of the pixel grid with the Pythagorean theorem and divide by the diagonal size in inches.
- Pixels to inches: inches = pixels ÷ DPI. Example: 3000 pixels at 300 DPI is 10 inches, or 25.4 cm.
- Inches to pixels: pixels = inches × DPI. Example: 8 inches at 300 DPI needs 2400 pixels.
- Screen PPI: PPI = √(width² + height²) ÷ diagonal. Example: a 27-inch 1920 × 1080 monitor has a pixel diagonal of 2202.9, so 2202.9 ÷ 27 = 81.59 PPI.
How many DPI do you really need?
It depends on how closely people will look at the result. For photographs, brochures, business cards and books, which are held at arm's length or closer, 300 DPI is the usual target because the eye can no longer pick out individual dots. For posters, banners and large wall prints that are viewed from a meter or more, 150 DPI often looks perfectly good, and billboards viewed from the road can drop far lower. Photo labs and online print services usually publish a minimum resolution for each product, so check their upload page if you can.
Large prints are a good illustration of why pixel count matters more than any DPI tag. A modern 12-megapixel phone photo is about 4000 × 3000 pixels. At 300 DPI that is a bit over 13 inches wide, enough for a very sharp 8×10. Stretch the same file to a 24×36 poster and the density falls to about 111 DPI, which is acceptable from across the room but visibly soft up close. Cropping makes things worse, because you throw away pixels you need.
Why Bilişim Ajans' DPI calculator?
This calculator does only what its name says and does it quickly. It combines pixel-to-inch conversion, print requirements and screen density in a single page, so you do not have to hop between three different tools. The values are processed locally in your browser with JavaScript. There is no upload, no account and no tracking, and after the first visit the page keeps working without a connection. The interface is built for phones as well as desktops, and every control can be used with the keyboard.