Case 1
- Width in pixels
- 1920px
- Height in pixels
- 1080px
- Diagonal in inches
- 24in
91.79ppi
Open with these valuesPPI Calculator
91.79ppi
Result: 91.79 ppiPPI is the diagonal measured in pixels divided by the diagonal measured in inches. Full HD on a 24-inch monitor gives 91.79 ppi; the same 3840 × 2160 is 163 ppi on a 27-inch desktop panel but 282 ppi on a 15.6-inch laptop. Resolution alone says nothing — the physical size decides.
Worked examples
Case 2
- Width in pixels
- 2560px
- Height in pixels
- 1440px
- Diagonal in inches
- 27in
108.79ppi
Open with these valuesCase 3
- Width in pixels
- 3840px
- Height in pixels
- 2160px
- Diagonal in inches
- 15.6in
282.42ppi
Open with these valuesHow it's calculated
PPI = √(width² + height²) ÷ diagonal
- StepEnter the horizontal and vertical resolution in pixels.
- StepEnter the diagonal in inches — the number the screen is sold by.
- ResultRead the pixel density; roughly 90 to 110 ppi is a normal desktop monitor.
Reference table
| Resolution, diagonal | Device | PPI |
|---|---|---|
| 1920, 1080, 24 | Full HD desktop monitor | 91.79 |
| 2560, 1440, 27 | QHD desktop monitor | 108.79 |
| 3840, 2160, 27 | 4K desktop monitor | 163.18 |
| 3840, 2160, 15.6 | 4K laptop panel | 282.42 |
| 1000, 1000, 10 | square panel | 141.42 |
Questions
How do I calculate PPI?
Find the diagonal in pixels with the Pythagorean theorem, then divide by the diagonal in inches. For 1920 × 1080 on a 24-inch screen that is √(1920² + 1080²) ÷ 24, about 91.79 ppi.
What is a good PPI for a monitor?
Most desktop monitors sit around 90 to 110 ppi, which looks sharp at arm's length. High-resolution laptops pass 150 ppi and phones reach several hundred, where single pixels stop being visible. How far away you sit matters as much as the number.
What is the difference between PPI and DPI?
PPI describes pixel density on a display; DPI describes the ink dots a printer lays down per inch. The two words get swapped freely, but PPI is the correct one for screens.
Why do two screens with the same resolution differ in PPI?
Because density depends on physical size as well as resolution. The same 1920 × 1080 is 91.79 ppi on a 24-inch monitor and well over 400 ppi on a phone, since the smaller screen packs the same pixels into far less space.
How does dot pitch relate to PPI?
Dot pitch is the distance between neighbouring pixel centres and is simply 25.4 mm divided by the PPI. A smaller pitch means denser pixels, so 0.10 mm is sharper than 0.28 mm.
Sources and last check
Information, not professional advice.