PPI Calculator

About PPI Calculator

PPI (Pixels Per Inch) measures how densely pixels are packed on a screen. Higher PPI means sharper text, crisper images, and less visible pixelation. This calculator takes a screen's resolution and diagonal size and returns the PPI, total pixel count, aspect ratio, physical dimensions, and a density classification. It runs entirely in your browser.

How PPI Is Calculated

The formula uses the Pythagorean theorem to find the diagonal resolution in pixels, then divides by the physical diagonal in inches: PPI = sqrt(width_px^2 + height_px^2) / diagonal_inches.

Display	Resolution	Diagonal	Diagonal Pixels	PPI
24" office monitor	1920 x 1080	24"	2,203	91.8
27" 4K monitor	3840 x 2160	27"	4,406	163.2
14" MacBook Pro	3024 x 1964	14.2"	3,605	253.9
iPhone 15 Pro	2556 x 1179	6.1"	2,815	461.5
iPad Pro 12.9"	2732 x 2048	12.9"	3,415	264.7

A 24" 1080p monitor has 92 PPI, while an iPhone 15 Pro packs 461 PPI into a 6.1" screen. That 5x density difference is why text looks razor-sharp on phones but can appear slightly soft on large desktop monitors.

PPI Density Classifications

Classification	PPI Range	Typical Devices	Pixel Visibility
Low density	Under 100	Large desktop monitors at 1080p (27"+)	Individual pixels clearly visible
Standard density	100-149	24" 1080p monitors, older laptops	Pixels visible if you look closely
High density	150-199	27" 4K monitors, some tablets	Pixels hard to see at arm's length
Retina / HiDPI	200-299	MacBooks, iPad Pro, Surface laptops	Pixels invisible at normal distance
Super high density	300-399	Flagship phones (Samsung Galaxy S24)	Indistinguishable from print
Ultra high density	400+	iPhone Pro models, Sony Xperia	Beyond human visual acuity at any distance

Apple coined "Retina display" to mean pixels are too small to see at the typical viewing distance. For phones held at 25-30 cm, that threshold is about 300 PPI. For laptops at 45-60 cm, about 220 PPI. For desktop monitors at 60-80 cm, about 150 PPI.

PPI vs DPI vs Device Pixel Ratio

These terms are related but distinct, and they are often confused.

Term	Meaning	Context
PPI (Pixels Per Inch)	Physical pixel density of a screen	Display hardware specs
DPI (Dots Per Inch)	Ink dots per inch in print	Printers and print design
Device Pixel Ratio (DPR)	Physical pixels / CSS pixels	Web development (window.devicePixelRatio)
Logical resolution	Resolution the OS reports to apps	macOS "looks like 1800x1169" on MacBook Pro

A MacBook Pro 14" has 3024 x 1964 physical pixels but macOS reports a logical resolution of about 1512 x 982 at the default setting. That gives a DPR of 2x, meaning each CSS pixel is rendered with 4 physical pixels (2 x 2). Web developers use DPR to serve appropriately sized images. Check your current device's DPR with the Screen Resolution Checker.

Why PPI Matters for Designers

Design Decision	How PPI Affects It
Image resolution	A 100x100px image looks fine at 96 PPI but blurry on a 2x Retina display - serve 200x200px for crisp rendering
Font rendering	Fonts on low-PPI screens need hinting (subpixel adjustments) to look sharp - high-PPI screens render any font smoothly
Icon design	1px borders and fine details disappear on low-PPI screens - design for the lowest target PPI
Print preparation	A 300 PPI image printed at 100% looks the same as on a 300 PPI screen, but a 96 PPI screen image prints at roughly 1/3 the quality
UI element sizing	A 44px touch target is 0.46" on a 96 PPI screen but only 0.10" on a 460 PPI phone - use physical size, not just pixels

Common Screen Resolutions and Their PPI

Resolution Name	Pixels	PPI at 24"	PPI at 27"	PPI at 32"
Full HD (1080p)	1920 x 1080	91.8	81.6	68.8
QHD (1440p)	2560 x 1440	122.4	108.8	91.8
4K UHD	3840 x 2160	183.6	163.2	137.7
5K	5120 x 2880	244.8	217.6	183.6

This is why a 27" 4K monitor (163 PPI) looks noticeably sharper than a 27" 1440p (109 PPI), and why the Apple Studio Display at 27" 5K (218 PPI) achieves true Retina quality at desktop viewing distances.

Print PPI (DPI) Requirements

Print Type	Required DPI	Pixels Needed for A4 (210 x 297mm)
Newspaper / web use	72-96	595 x 842
Standard print (flyers, books)	300	2,480 x 3,508
High-quality print (photo books)	300-600	2,480 x 3,508 minimum
Large format (posters, banners)	150	1,240 x 1,754 (A4 equivalent)

The standard for professional print is 300 DPI. Images below this threshold appear pixelated when printed. For large-format prints viewed from a distance (posters, banners), 150 DPI is usually sufficient.

For checking your current device's screen resolution and DPR, the Screen Resolution Checker reads those values directly. For mapping image dimensions to different aspect ratios, try the Aspect Ratio Calculator. All calculations run in your browser.