Check Image DPI — Free, Fast & Private
DPI (dots per inch) determines how sharp an image looks when printed. A 3000x2000 pixel photo at 300 DPI prints beautifully at 10x6.67 inches. The same photo at 72 DPI would need to print at 41.7x27.8 inches to use all its pixels — fine for a billboard, terrible for a business card.
Here is the part that confuses most people: DPI is a print concept. On screens, only pixel dimensions matter. A 1920x1080 image displays identically at 72 DPI and 300 DPI on a monitor. The DPI metadata only affects how a printer or design application interprets the image size. So when someone says "make this image 300 DPI," what they usually mean is "make sure it has enough pixels to print sharply at the intended size."
To calculate what you need: multiply the print size in inches by the required DPI. A 4x6 inch photo at 300 DPI needs 1200x1800 pixels. An A4 page (8.27x11.69 inches) at 300 DPI needs 2481x3507 pixels. If your image has fewer pixels than required, it will look soft or pixelated when printed.
Phone cameras produce more than enough pixels for most print needs. A 12MP phone camera captures 4032x3024 pixels — that is enough for a 13.4x10 inch print at 300 DPI. The file will likely say 72 DPI in its metadata, but that is just a default tag. The actual pixel count is what matters.
MiniPx shows you the pixel dimensions and file size of any image you upload. For print work, divide the pixel dimensions by your required DPI to calculate the maximum sharp print size. For web use, pixel dimensions are all you need to check.