What it is
The PPI (pixels‑per‑inch) calculator measures how tightly packed the pixels of a screen are, allowing developers and reviewers to compare how sharp an image will appear on different displays. By inputting the horizontal and vertical pixel counts along with the physical diagonal size in either inches or centimetres, you derive the linear pixel density using the standard formula √(width²+height²)/diagonal_in_inches. Knowing this metric is essential for mobile developers to set image resolutions that look crisp on a variety of devices, for reviewers to weigh display quality against competition, and for engineers when designing panels or assembling custom screens. PPI directly influences perceived sharpness; a higher value means fewer pixel gaps and smoother text/images.
How to use it
Enter the total horizontal pixels in "Resolution width", then the vertical pixels in "Resolution height". Next put the screen’s diagonal length into "Diagonal size" – pick inches or centimetres from the dropdown. The calculator instantly produces the PPI value rounded to three decimals. Use this figure to compare across devices or verify that your design meets a target pixel density.
Worked example
For a 1080×2400‑pixel display with a 5.7‑inch diagonal: 1) Compute the pixel diagonal: √(1080² + 2400²)=√6,926,400≈2631.805 pixels. 2) Divide by the physical size in inches: 2631.805 / 5.7≈461.721 PPI. The tool displays 461.721 after rounding to three decimals.
Inputs
- Resolution width (pixels): 1080
- Resolution height (pixels): 2400
- Diagonal size: 5.7
- Size unit: 0
Result
- Pixels per inch (PPI): 461.721
Frequently asked questions
Can I use millimetres for the diagonal size?
No – the calculator accepts only inches or centimetres. If you have millimetres, first convert them to centimetres (divide by 10) and then input the value with “Centimetres” selected.
Does PPI include the screen's bezel or border area?
PPI is calculated solely from pixel resolution and physical diagonal length; it does not account for bezels. To compare effective display area, use the effective pixel area divided by the adjusted diagonal after subtracting bezel width.
How should I interpret a PPI of 300 versus 400 on smartphones?
A higher PPI yields sharper images because each inch hosts more pixels. However differences below about 60 PPI are typically imperceptible at normal viewing distances; beyond ~200‑300 PPI you may notice a clear improvement, especially for text and small UI elements.