DPI Calculator
Give the calculator your pixel dimensions and the size you intend to print, and it returns the effective DPI along with a verdict on whether that density holds up in print.
Leave the height blank to work from the width alone.
How to calculate DPI
Divide the pixel dimension by the printed dimension in inches: DPI = pixels ÷ inches. A 3000 pixel wide photo printed 10 inches across is 3000 ÷ 10 = 300 DPI.
Do it for both edges. If the width and height give different answers your image will be cropped or stretched to fit, and the smaller of the two numbers is the density you will actually get.
Worked with the values in the calculator above
DPI across width = 2,550 px ÷ 8.5 in = 300 DPI
DPI across height = 3,300 px ÷ 11 in = 300 DPI
usable density = the smaller of the two = 300 DPI What DPI do you need?
Match the density to viewing distance rather than to a rule. 300 DPI is the standard for photographs, magazines and anything held in the hand. 150 DPI is enough for posters read from a metre away. Large-format banners are routinely produced at 30 to 72 DPI because nobody stands close enough to resolve the difference.
Raising the DPI of an existing file in an image editor does not add detail. It only changes the tag; the pixel count, and therefore the real resolution, stays the same.
At the density above
One inch square at 96 PPI
96 × 96 = 9,216 pixels fill this square.
Frequently asked questions
What DPI is a 4000 × 3000 photo printed at 10 × 8 inches?
375 DPI. The width gives 4000 ÷ 10 = 400 and the height 3000 ÷ 8 = 375, and the smaller one is what you get — the 4:3 photo also loses about 6% of its long edge to fit the 5:4 print.
How do I work out the DPI of an image?
Read the pixel dimensions from the file properties, decide the size you want to print, and divide. The calculator above does both edges at once and flags whether the result is print quality.
What is a good DPI for printing?
300 DPI for photos and anything read close up, 150 DPI for posters, and less than 100 DPI only for large signage viewed from several metres away.
Can I increase the DPI of an image?
You can change the tag, but not the detail. Print the same pixels smaller and the DPI rises genuinely; resample upwards and the software is inventing pixels that were never captured.
Is DPI the same as resolution?
No. Resolution is the pixel count, DPI is how tightly those pixels are packed onto paper. The same file can be printed at any DPI you like — only the physical size changes.