Screen Resolution / PPI Calculator
How it works
Width and height in pixels are not a screen's diagonal pixel count — that takes the same Pythagorean step used to find its physical diagonal size: diagonalPx = √(width² + height²). PPI is then that diagonal pixel count divided by the diagonal size in inches you entered, so it answers "how many pixels per inch, along the diagonal" — and, because the panel's pixels are laid out in a uniform grid, that same figure also applies horizontally and vertically.
The aspect ratio is the width and height reduced to their simplest whole-number form, found by dividing both by their greatest common divisor — precisely how a fraction like 1920/1080 reduces to 16/9.
Frequently asked questions
What is PPI actually used for?
It is the number that lets you compare sharpness across screens of different sizes and resolutions. A higher PPI generally means sharper text and images at normal viewing distance, which is why it is worth checking alongside resolution when comparing two monitors, or two phones, that pack the same pixel count into different physical sizes.
How is the aspect ratio simplified?
The same way a fraction is reduced: both numbers are divided by their greatest common divisor. 1920×1080 and 3840×2160 both reduce to 16:9 because 1920/1080 and 3840/2160 are the same ratio at different scales — dividing each by its own GCD (120 and 240, respectively) leaves the same simplest form.
Why show diagonal resolution in pixels alongside PPI?
It is a different quantity from the diagonal size you typed in, and easy to conflate with it. The diagonal SIZE (in inches) is how big the screen physically is; the diagonal RESOLUTION (in pixels) is how many pixels are packed along that same line. PPI is exactly the second divided by the first, so seeing both numbers next to the result makes that division easy to check by hand.