PPI Calculator
How sharp is a 27" 1440p monitor, really? Enter a resolution and diagonal size — or tap a preset — to get pixels per inch, dot pitch, total megapixels, and the aspect ratio.
Pixel density
108.8
PPI
Dot pitch
0.233
mm
Total pixels
3.7 MP
3,686,400 px
Aspect ratio
16:9
PPI = √(width² + height²) ÷ diagonal inches; dot pitch is its inverse, 25.4 ÷ PPI in mm. Rough comfort guides: ~90+ PPI for desktop monitors at arm's length, ~220 PPI for “Retina” laptops, 450+ PPI for phones held close.
Pixel Density, Explained
PPI is the diagonal pixel count divided by the diagonal in inches. A 27" 2560×1440 monitor has √(2560² + 1440²) = √8,627,200 ≈ 2937.2 pixels across its diagonal, so 2937.2 ÷ 27 = 108.8 PPI — with a dot pitch of 25.4 ÷ 108.8 = 0.233 mm between pixel centers. A 24" 1080p panel lands at a similar 91.8 PPI, which is why those two combinations are the comfortable desktop standards; stretch 1080p to 27" and density drops to 81.6 PPI, where text starts looking soft at arm's length.
Formula & common displays
PPI = √(width² + height²) ÷ diagonal inches Dot pitch (mm) = 25.4 ÷ PPI 24" 1080p 91.8 PPI 27" 1440p 108.8 PPI 27" 4K 163.2 PPI 32" 4K 137.7 PPI 13.6" MacBook Air (2560×1664) 224.5 PPI 6.1" phone (2556×1179) 461.4 PPI
Frequently Asked Questions
Is 1080p good enough at 27 inches?
1920×1080 at 27" works out to only 81.6 PPI — text looks noticeably soft at a normal 2–3 ft desk distance, and many people find anything under ~90 PPI pixelated. The 27" sweet spot is 2560×1440 at 108.8 PPI; if you want 1080p, 24" (91.8 PPI) is the better fit.
What PPI counts as a Retina display?
"Retina" is Apple's term for densities where the eye can't resolve individual pixels at typical viewing distance — roughly 220 PPI for laptops and 450+ for phones. The 13.6" MacBook Air (2560×1664) hits 224 PPI, and a 6.1" phone at 2556×1179 reaches 461 PPI. Desktop monitors viewed from farther away get by with far less.
What is dot pitch and how does it relate to PPI?
Dot pitch is the physical distance between adjacent pixel centers, in millimeters — the inverse of density: dot pitch = 25.4 ÷ PPI. A 27" 1440p monitor at 108.8 PPI has a 0.233 mm dot pitch. Smaller pitch means finer detail; spec sheets sometimes list pitch instead of PPI.
Does a bigger screen at the same resolution lower the PPI?
Yes — the same pixel count spread over more inches means lower density. 4K (3840×2160) is 163.2 PPI on a 27" panel but drops to 137.7 PPI at 32". That's why a 65" 4K TV (67.8 PPI) still looks sharp from a couch but soft at desk distance: PPI only tells the full story together with viewing distance.