Photo Print Size & DPI Calculator
Enter your image pixel dimensions to see which print sizes are achievable at great, good, and acceptable quality. Or reverse it: enter a target print size to find the minimum megapixels needed. Nothing uploaded.
Image Details
Maximum Print Sizes
Learn more: print resolution and DPI
Pixels per inch, and why 300 is not a hard limit
The tool divides your pixel dimensions by the print size to get pixels per inch, which it labels DPI. At 300 you get the top rating. An 8x10 inch print at 300 needs 2,400 x 3,000 pixels, 7.2 megapixels. At 150 it needs 1,200 x 1,500, which is 1.8 megapixels, a quarter as many.
Wikipedia's pixel density article says that if a poster, banner or billboard will be viewed from far away, a much lower PPI is possible, and that this matters most on large formats. So a print on a wall seen from several feet needs fewer pixels than a photo book held close.
Worked example
A 4000 x 3000 pixel photo is 12 megapixels. The tool gives these maximum print sizes: 13.3 x 10 inches at 300 DPI, 20 x 15 at 200, 26.7 x 20 at 150 and 40 x 30 at 100. On the preset paper sizes the ratings are great for 4x6, 5x7, 8x10 and A4, good for 11x14 and A3, ok for 16x20, 20x24 and A2, and poor for 24x36.
When the photo and the paper have different shapes, the tool uses the lower of the two edge values. For 16x20, the long edge gives 4000 / 20 = 200 and the short edge 3000 / 16 = 187.5. The result is 187.5, shown as 188, which is the ok tier. This assumes you scale the photo to fill the paper and crop what hangs over.
The tiers are the tool's own: great at 300 or more, good from 200, ok from 150 and poor below 150.
FAQ
What is the difference between DPI and PPI?
Wikipedia explains that a pixel is a single sample of any color, while an inkjet print can only print a dot of a specific color on or off, so printers use dithering. PPI describes the image and DPI describes the printer. Calculators, this one included, often use DPI for the image's pixels per inch.
Is 150 DPI too low?
Not automatically. The tool rates 150 as ok. Viewing distance matters, and a large print seen from across a room can look fine at a figure that looks soft in a small print held close.
How many megapixels do I need for an 8x10?
7.2 megapixels for 300 DPI, or 1.8 megapixels for 150. A 16x20 needs 28.8 megapixels at 300.