🔍 /

PPI (Pixels Per Inch) & Retina Distance Calculator

Determine screen sharpness and "Retina" viewing distance. Compare pixel density across monitors, smartphones, and tablets.

User Rating 0.0 ★★★★★
Total Usage 0 times
Category System & Hardware
Quick Presets:
Is this tool helpful?

Your feedback helps us improve.

★ ★ ★ ★ ★

About

Pixel density, measured in PPI (Pixels Per Inch), is the definitive metric for display sharpness. Unlike resolution (e.g., 4K, 1080p), which only counts total pixels, PPI relates those pixels to the physical size of the screen. High PPI is critical for graphic design, photo editing, and text legibility. A 27-inch 1080p monitor (81 PPI) will appear significantly blockier than a 27-inch 4K monitor (163 PPI).

This tool also calculates the "Retina Distance" - the physical distance from the screen where the human eye with 20/20 vision can no longer distinguish individual pixels. This concept, popularized by mobile manufacturers, is based on the limit of human visual acuity (approximately 1 arcminute). If you sit closer than the calculated Retina Distance, you may see pixelation; if you sit further away, the display appears perfectly smooth.

PPI calculator retina distance screen density monitor resolution pixel pitch

Formulas

We first calculate the diagonal pixel count dpx using the Pythagorean theorem on the horizontal (wpx) and vertical (hpx) resolution.

dpx = √wpx2 + hpx2

Then, PPI is the ratio of diagonal pixels to the physical diagonal size Din.

PPI = dpxDin

The Retina Distance Rdist is derived from the limit of visual acuity (1 arcminute). For 20/20 vision, the constant 3438 is used.

Rdist = 3438PPI (inches)

Reference Data

Device / StandardScreen SizeResolutionDensity (PPI)Retina Dist.
Apple Watch Ultra1.92in502×410338 PPI10 in
iPhone 14 Pro6.1in2556×1179460 PPI7.5 in
iPad Pro 12.912.9in2732×2048264 PPI13 in
MacBook Pro 1616.2in3456×2234254 PPI13.5 in
Standard 24" Monitor23.8in1920×108092 PPI37 in
27" 4K Monitor27in3840×2160163 PPI21 in
Ultrawide 34"34in3440×1440110 PPI31 in
8K TV 85"85in7680×4320104 PPI33 in

Frequently Asked Questions

[{"question":"What is a "good" PPI for a monitor?","answer":"For desktop use (viewing distance ~20-30 inches), 100-110 PPI is standard (e.g., 27\" 1440p). 140+ PPI (e.g., 27\" 4K) is considered "Retina-grade" for desktops, where pixels are invisible at normal distances. For phones, you typically want 300+ PPI due to closer viewing distances."},{"question":"Why is PPI more important than total resolution?","answer":"Resolution (e.g., 1080p) tells you nothing about sharpness without knowing the size. A 1080p smartphone is incredibly sharp; a 1080p 65-inch TV is quite blurry if you sit close. PPI standardizes this measurement across all sizes."},{"question":"How is the Retina Distance calculated?","answer":"It uses the angular resolution of the human eye. The average person with 20/20 vision cannot resolve details smaller than 1/60th of a degree. The formula calculates how far away pixels of a certain density must be to subtend that angle."},{"question":"Does higher PPI affect battery life?","answer":"Yes. Higher density displays (like 4K on a laptop) require the GPU to push 4x more pixels than 1080p, consuming more power. Additionally, the backlight often needs to be brighter to shine through the denser transistor matrix."}]