Calculators
PPI calculator
PPI is the number of pixels per inch of screen. Enter the resolution and diagonal to get the density and find out whether the pixel grid is visible from a typical distance for the device.
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How we calculate
Pixel density
PPI = √(width_px² + height_px²) / diagonal_in
“Pixels invisible” threshold
PPI ≥ 1 / (distance_in · tan 1′) ≈ 3438 / distance_in
- The threshold assumes 20/20 vision: the eye resolves details of about 1 arcminute.
- Typical distances: phone 30 cm, tablet 40 cm, laptop 50 cm, monitor 65 cm, TV 2.5 m. The farther the screen, the lower the PPI it needs.
- PPI isn't the only factor: subpixel layout (PenTile on OLED), scaling and font smoothing also affect sharpness.
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Frequently asked questions
How much PPI does a phone need?
From 30 cm, pixels blend from about 290 PPI. Modern phones (400+ PPI) clear that easily.
What PPI is good for a monitor?
From 65 cm about 135 PPI is enough: a 27″ 1440p (109 PPI) is just below, a 27″ 4K (163 PPI) is above.
Why do TVs have such low PPI?
You watch from 2–3 m: at 2.5 m about 35 PPI is enough, and a 55″ 4K has about 80.
Is my input sent anywhere?
No. Everything runs in your browser.