PPI / DPI Calculator

Find a screen pixel density (PPI) from its resolution and size.

Reviewed by the ToolNestr Editorial Team — July 2026

Horizontal resolution (px)

Vertical resolution (px)

Screen size (inches, diagonal)

How PPI works

Pixels per inch (PPI) measures how many pixels fit into one linear inch of a display. The higher the PPI, the sharper and more detailed the image appears. To calculate it, you need the screen resolution (width and height in pixels) and the diagonal size of the display in inches.

The diagonal pixel count is found using the Pythagorean theorem — treating the width and height as the legs of a right-angled triangle and the diagonal as the hypotenuse. Once you know how many pixels span the diagonal, dividing by the diagonal length in inches gives you the PPI.

The formula

Diagonal pixels = √(w² + h²)

PPI = diagonal pixels / diagonal inches

Dot pitch = 25.4 / PPI (25.4 mm per inch)

Megapixels = (w × h) / 1 000 000

Worked example

Take a standard 1920 × 1080 Full HD laptop with a 15.6-inch screen.

diagonal px = √(1920² + 1080²) = √(3 686 400 + 1 166 400) = √4 852 800 ≈ 2203
PPI = 2203 / 15.6 ≈ 141.2 → 141 PPI
Dot pitch = 25.4 / 141.2 ≈ 0.18 mm
Megapixels = (1920 × 1080) / 1 000 000 = 2.07 MP

This is typical for a mid-range laptop. A 13-inch MacBook Pro at 2560×1600 clocks in at ~227 PPI — Apple’s "Retina" threshold.

Common resolutions and their PPI

The same resolution gives different PPI at different screen sizes. Here is how common display sizes compare.

Resolution	Size (inches)	PPI	Dot pitch	Notes
1920 × 1080	24"	92	0.28 mm	Desktop monitor
1920 × 1080	15.6"	141	0.18 mm	Laptop
2560 × 1440	27"	109	0.23 mm	QHD monitor
2560 × 1600	13.3"	227	0.11 mm	MacBook Pro Retina
3840 × 2160	32"	138	0.18 mm	4K monitor
3840 × 2160	27"	163	0.16 mm	4K small monitor
3840 × 2160	15.6"	282	0.09 mm	4K laptop
2532 × 1170	6.1"	460	0.06 mm	iPhone typical
2340 × 1080	6.4"	403	0.06 mm	Android phone
1920 × 1080	55"	40	0.64 mm	TV

Use cases for PPI

Comparing screen sharpness

PPI gives you an objective number to compare how sharp different displays will look — regardless of their size or resolution. A 6-inch phone at 400 PPI will look noticeably crisper than a 24-inch monitor at 92 PPI, even though the monitor has more total pixels.

Checking retina status

Apple’s "Retina" branding means the pixel density exceeds what the human eye can distinguish at a typical viewing distance. For phones (~12 inches away) that threshold is ~300 PPI. For laptops (~20 inches) it is ~200 PPI. Use this tool to see if your display qualifies.

Design and print specs

When designing for a specific device, knowing its PPI helps you create assets at the right resolution. A UI element that looks crisp on a 72 PPI monitor may be too small or blurry on a 200 PPI laptop. Designers use PPI to scale icons, fonts, and spacing accurately.

Evaluating dot pitch

Dot pitch (pixel pitch) is the physical distance between pixel centres. A smaller dot pitch means pixels blend together, producing smoother images — important for photo editing, video production, and reading small text. A dot pitch below 0.2 mm is generally considered very sharp.

Tips for interpreting PPI

PPI alone is not everything

Perceived sharpness depends heavily on viewing distance. A 55-inch 4K TV at 80 PPI looks perfectly sharp from 8 feet away, while a 24-inch 1080p monitor at 92 PPI may look pixelated from 2 feet. Always factor in how far you sit from the screen.

Higher PPI costs more

Higher density displays are more expensive to manufacture and require more GPU power to drive. A 4K laptop screen (282 PPI at 15.6") demands significantly more graphical performance than a 1080p panel (141 PPI) at the same size, which impacts battery life.

DPI vs PPI

DPI (dots per inch) is often used interchangeably with PPI, but strictly speaking PPI refers to pixel displays while DPI refers to print. A 300 DPI print standard means the same thing as 300 PPI on screen — both describe 300 dots or pixels per inch.

Downsampling affects perceived sharpness

Some high-PPI displays run at a lower native resolution for compatibility, which can reduce sharpness. macOS uses HiDPI mode (rendering at 2× scale) so a Retina display always maps logical pixels to physical pixels 1:2, keeping text razor-sharp.

PPI across device categories

Smartphones

Modern flagship phones typically land between 400 and 500 PPI. With a viewing distance of 10–12 inches, text and icons appear completely smooth. Even budget phones rarely dip below 300 PPI, which is the recognised threshold for "retina" quality at typical phone distances.

Laptops

Laptop PPI ranges widely — from ~100 PPI on budget 1080p 17-inch models to ~227 PPI on a 13-inch MacBook Pro at 2560×1600. The viewing distance is typically 18–24 inches, so 200+ PPI is generally considered retina-quality for laptops.

Desktop monitors

Most desktop monitors sit at 90–140 PPI depending on resolution and size. A 27-inch 4K monitor (163 PPI) is noticeably sharper than a 24-inch 1080p (92 PPI). For text-heavy work like coding or writing, higher PPI reduces eye strain significantly.

TVs

Televisions typically range from 40–90 PPI because they are viewed from much farther away. A 55-inch 4K TV is ~80 PPI, but from a 6–10 foot viewing distance, individual pixels are invisible. Going beyond 4K at typical TV sizes offers diminishing returns at normal seating distances.

Why megapixels matters

Total megapixels (width × height / 1 000 000) tells you how many million individual pixels the display contains. This is useful for understanding the sheer amount of detail a screen can show. A 4K display (3840×2160) has ~8.3 MP — about four times the 2 MP of a 1080p panel. Higher megapixel counts mean more room for content, sharper video playback, and better photo editing capabilities. However, more pixels also require more powerful graphics hardware to drive smoothly, especially for gaming or video editing.