PPI Calculator (Pixels per Inch)
Work out a screen's pixels per inch from its resolution and diagonal, plus dot pitch, physical width and height, and the distance where pixels disappear.
| Device | Resolution | Diagonal | PPI | Retina distance |
|---|---|---|---|---|
| iPhone 15 / 16 | 1179 × 2556 | 6.1″ | 461.4 | 7.4 in |
| iPhone 15 Pro Max | 1290 × 2796 | 6.7″ | 459.6 | 7.5 in |
| Galaxy S24 | 1080 × 2340 | 6.2″ | 415.7 | 8.3 in |
| iPad 10th gen | 2360 × 1640 | 10.9″ | 263.7 | 13 in |
| MacBook Air 13.6″ | 2560 × 1664 | 13.6″ | 224.5 | 15.3 in |
| MacBook Pro 14″ | 3024 × 1964 | 14.2″ | 253.9 | 13.5 in |
| 24″ Full HD | 1920 × 1080 | 24″ | 91.8 | 37.5 in |
| 27″ QHD | 2560 × 1440 | 27″ | 108.8 | 31.6 in |
| 27″ 4K | 3840 × 2160 | 27″ | 163.2 | 21.1 in |
| 32″ 4K | 3840 × 2160 | 32″ | 137.7 | 25 in |
| 55″ 4K TV | 3840 × 2160 | 55″ | 80.1 | 42.9 in |
Pixel density — pixels per inch, PPI — tells you how sharp a screen looks: the same 1920 × 1080 picture is crisp on a 13-inch laptop and coarse on a 32-inch monitor. Enter a resolution and diagonal (or pick a device) to get PPI, the dot pitch, the physical width and height of the panel, and the viewing distance beyond which individual pixels disappear for normal vision.
How to use this tool
- Pick a device preset, or keep "Custom" and enter the resolution in pixels.
- Enter the diagonal screen size and choose inches or centimetres.
- Read the PPI and dot pitch; compare with common screens in the table.
- Use the retina distance to judge whether a screen looks sharp from where you sit.
Formula
PPI = √(w² + h²) ÷ diagonal · dot pitch (mm) = 25.4 ÷ PPI · width = diagonal × w ÷ √(w² + h²) · retina distance = 1 ÷ (PPI × tan 1′)
w and h are the pixel counts, the diagonal is in inches. 1′ (one arcminute, 1/60°) is the detail limit of 20/20 vision, so 1 ÷ tan 1′ ≈ 3438.
Example
A 24-inch 1920 × 1080 monitor has a diagonal of √(1920² + 1080²) = 2202.9 pixels, so 2202.9 ÷ 24 = 91.79 PPI and a dot pitch of 0.2767 mm. The panel is 20.92 × 11.77 inches, and pixels blend together from about 37.5 inches (95 cm) away.
Frequently asked questions
Is PPI the same as DPI?
Not quite. PPI describes pixels on a screen or in an image; DPI is ink dots a printer lays down. People often use them interchangeably, and image files store the "DPI" setting as pixels per inch.
What PPI counts as "retina"?
It depends on viewing distance: about 300 PPI for a phone at 25–30 cm, around 220 for a laptop and 110–140 for a desktop monitor at arm's length look free of visible pixels.
Why does my result differ slightly from the spec sheet?
Makers round the diagonal and sometimes measure the visible area differently (rounded corners, notches). A difference of a few PPI is normal.
Last updated:
Page address with these inputs: https://kakao.mobile/tools/ppi-calculator/
Cite or embed this tool
kakaoCalc. (2026, November 8). PPI Calculator (Pixels per Inch). https://kakao.mobile/tools/ppi-calculator/
“PPI Calculator (Pixels per Inch).” kakaoCalc, 8 Nov. 2026, kakao.mobile/tools/ppi-calculator/.
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