Find a screen’s pixel density (PPI) from its resolution and physical diagonal size.
How it works
The diagonal pixel count is found the same way as the physical diagonal, then divided by the physical diagonal in inches: PPI = √(width² + height²) ÷ diagonal. A 1920×1080 screen with a 24-inch diagonal has about 92 PPI.
What this does not include
This is distinct from this site’s screen size calculator, which finds physical diagonal size from width and height rather than pixel density from resolution.
How to use this calculator
- Enter the horizontal and vertical resolution in pixels.
- Enter the screen’s physical diagonal size.
A worked example
A 1920×1080 display with a 24-inch diagonal: PPI = 91.7878.
A 3840×2160 display with a 27-inch diagonal: PPI = 163.1783 — 4× the pixels on a similarly sized screen means noticeably sharper detail.
What the variables mean
| Variable | Meaning |
|---|---|
| Width, height (px) | Screen resolution in pixels |
| Diagonal | Physical screen size, measured diagonally in inches |
Edge cases worth knowing
The same resolution on a larger screen produces a lower PPI. Higher PPI generally means sharper, more detailed images, which is why a 4K display looks noticeably crisper than a Full HD display at a similar physical size.
A width of zero makes the calculation meaningless, so the calculator declines to show a result for that input.
Why does a smartphone screen have much higher PPI than a TV?
A phone packs a similar or higher pixel count into a much smaller physical diagonal, so its pixels are packed far more densely — this is exactly why phone screens look sharp even held close to the eye.
What PPI is considered “sharp” to the human eye?
Around 300 PPI or higher is often cited as the point where individual pixels become difficult to distinguish at typical smartphone viewing distances, though this varies with actual viewing distance.
Does higher PPI always mean a better display?
Not necessarily — color accuracy, contrast, brightness, and refresh rate all matter too; PPI measures only how densely packed the pixels are, not overall image quality.
