About the DPI Calculator
When a digital image is printed, its pixels are spread across the paper. The more pixels there are in each inch, the finer the detail looks; the fewer there are, the more the print looks soft or blocky up close. That density is the image's DPI, dots per inch, and it is the single most useful number for knowing whether a photo or design will print well at the size you want.
This DPI calculator works out the print resolution from an image's pixel width and the width it will be printed, in inches or centimetres. It gives the DPI, the full print size including the height, a quality rating, the largest print at 300 DPI, and the size or density in the other unit system.
How to Use the DPI Calculator
Enter the image width and image height in pixels. You can find these in the file's properties or in any image editor.
Enter the printed width — how wide the image will be on paper.
Choose the unit for that width, inches or centimetres.
The calculator divides the pixels by the inches to find the DPI, and works out the printed height from the image's shape.
How DPI Is Worked Out
DPI = pixel width ÷ printed width in inches
inches = centimetres ÷ 2.54
printed height = pixel height ÷ DPI
largest print at 300 DPI = pixel width ÷ 300 by pixel height ÷ 300Step-by-Step Example
A 3000 × 2000 pixel image printed 10 inches wide.
DPI: 3000 px ÷ 10 in = 300 DPI
Height: 2000 px ÷ 300 = 6.67 in
Print: 10 × 6.67 in (25.4 × 16.9 cm)
Rating: excellent — photo qualityThe same image printed 25.4 cm wide gives the same answer: 25.4 ÷ 2.54 is 10 inches, so it is still 300 DPI, which is about 118 dots per centimetre.
A 1920 × 1080 image, the size of a Full HD screen, printed 20 inches wide is only 96 DPI. That is fine on a wall seen from across the room, but it will look soft and pixelated close up. At 300 DPI the same image prints at just 6.4 × 3.6 inches.
How Much DPI Is Enough?
The DPI you need depends on how closely the print will be viewed.
300 DPI or more photo quality, prints held in the hand
200 – 300 DPI good for most prints and framed pictures
150 – 200 DPI fine for posters and prints on a wall
under 150 DPI likely to look soft up closeThe eye can only pick out so much detail at a given distance. A photo held at reading distance shows every flaw, while a poster seen from a couple of metres away can have half the density and look just as sharp. Billboards, read from across a road, are often printed at 20 to 50 DPI.
DPI, PPI and the File Setting
Strictly, PPI is pixels per inch in the image, and DPI is dots of ink per inch laid down by a printer, which uses several dots of ink to reproduce each pixel's colour. In everyday use, and in most software, DPI is used for both, and this calculator follows that habit.
Image files also carry a stored DPI value, often 72 or 300. That number is only a note of the intended print size. Changing it in an editor without resampling leaves every pixel as it was and simply changes the printed size the file suggests. What really matters is the pixel count and the size you print at.
Improving a Low DPI
If the DPI comes out too low, the simplest fix is to print smaller. Each halving of the print width doubles the DPI. Cropping less of the photo also helps, since cropping throws away pixels. Upscaling software can smooth the result and make the edges less jagged, but it cannot add real detail that the camera did not capture, so start from the largest original you have.
Phones, Cameras and Scans
A typical 12 megapixel phone photo is 4000 × 3000 pixels, which gives 300 DPI at about 13 × 10 inches, plenty for most home prints. A 24 megapixel camera reaches 300 DPI at 20 × 13.3 inches. Older phones and images saved from messaging apps are often much smaller, because many apps shrink photos before sending them, so check the pixel size of the actual file you plan to print rather than assuming it matches the camera.
Scanning works the other way round. A scanner set to 600 DPI captures 600 pixels for every inch of the original, so a 6 × 4 inch photo scanned at 600 DPI becomes 3600 × 2400 pixels. That is enough to reprint it at twice the size, 12 × 8 inches, at 300 DPI. Choose the scan resolution from how large you want the copy to be printed.
Checking Artwork for Print
Designers placing photos in a brochure or poster should check the DPI at the size each image appears on the page, not its size in the original file. Scaling a photo up in a layout lowers its effective DPI in proportion, so an image placed at twice its natural size drops from 300 to 150 DPI. Most layout programs show this as the effective resolution, and many printers will warn about images below 200 DPI.
Understanding Your Result
The headline is the DPI at the width you entered.
The print line gives the full print size, width by height, in your unit.
The quality rating places the DPI in bands from excellent to low.
The largest print at 300 DPI shows how big you can go at photo quality.
The metric line gives the print in centimetres, or the density in dots per centimetre if you entered centimetres.
When Should You Use This Calculator?
Use it before ordering prints, canvases or photo books to check each image will look sharp at the size chosen.
Use it when a printer or publisher asks for artwork at 300 DPI.
Use it to decide how large you can print a photo from a phone or camera.
Use it when designing posters, flyers or signs to check that placed images have enough resolution.
Common Mistakes
Changing the DPI setting and expecting sharper prints. The stored DPI does not change the pixels. Only more pixels, or a smaller print, raises the real resolution.
Using the screen size. An image may look large and sharp on a monitor while having too few pixels for a big print.
Mixing up inches and centimetres. DPI is per inch; divide centimetres by 2.54 first.
Insisting on 300 DPI for everything. Large prints seen from a distance can use much less, allowing bigger prints from the same image.
Forgetting the crop. Cropping a photo to fit a print shape removes pixels and lowers the DPI of what is left.