What is PPI?
Definition
PPI stands for pixels per inch. It measures how many pixels of an image are shown across one inch of a screen or print. For a photo, PPI equals its pixel width divided by the width in inches at which it is displayed, so a bigger display size means a lower PPI.
Why it matters for sellers
PPI explains why a photo can look sharp at one size and soft at another. The same pixels spread across a larger area give a lower PPI, and detail starts to fade. Sellers who print posters, tags or catalog pages need enough PPI at the final size.
PPI is a number about pixels, while DPI is about printer dots. Mixing them up leads to wrong choices, such as resaving a photo at a higher number and expecting more detail. Only more real pixels, or a smaller print size, raises the effective PPI.
How to do it with Instasize
Instasize helps you work out the PPI a print size would have, and check the pixels your photo contains.
- Open the Image Dimensions Checker and read your photo's pixel width and height.
- Open the Pixel to Print Size Calculator.
- Enter the pixel size and the PPI you want to see the print size, or enter a print size to see the pixels needed.
- If the photo has too few pixels, resize or upscale it, or choose a smaller print size.
Related Instasize pages
Examples
Phone screen versus poster
A phone shows a photo at a high PPI, so it looks crisp. The same photo printed on a large poster has a much lower PPI and looks softer.
Business card photo
A small product photo printed at a small size keeps a high PPI, so a low pixel count still looks clean.
Mixed-up numbers
A seller resaves a small photo with a larger PPI value in the file. The pixels are the same, so the printed result is just as soft.
Frequently asked questions
What is the difference between PPI and DPI?
PPI counts pixels in an image or on a screen per inch. DPI counts printer dots per inch. A printer may use several dots to reproduce one pixel.
How do I calculate PPI?
Divide the pixel width of the image by the width in inches at which it is shown or printed. The Pixel to Print Size Calculator does this for you.
Does a higher PPI always mean a better photo?
Not in itself. PPI depends on both the pixel count and the display size. A photo with many pixels shown small has a high PPI, but that says nothing about focus or lighting.
Can I raise PPI by changing the file setting?
Changing the stored number does not add pixels. To raise the real PPI at a given print size, you need more pixels or a smaller print.