Pixel density reference
Pixels Per Inch
Calculate screen PPI, compare pixel density across devices, and see every PPI value that matters for web, print, and UI work.
Classification
Standard
Classic desktop density, 1x pixel ratio
Formula: PPI = sqrt(width squared plus height squared) divided by diagonal in inches. Pick a preset to auto-fill a common screen, or type your own resolution and diagonal.
What Is Pixels Per Inch?
Pixels per inch is a measurement of pixel density. It tells you how many individual pixels a screen or image packs into one linear inch. Higher PPI means smaller, denser pixels. Lower PPI means larger, more visible pixels. PPI is the single most important number for judging how sharp a display will look at a given viewing distance.
The web reference pixel density is 96 PPI, a holdover from early Windows displays. Modern phones now ship at 400 to 500 PPI. The gap between those numbers is why CSS uses an abstract reference pixel rather than a physical one: at 96 PPI one CSS pixel equals one device pixel, but at 460 PPI a single CSS pixel is actually rendered with around 5 device pixels, preserving readable sizes across wildly different hardware.
PPI and DPI are used interchangeably in most software, but the technical split is clean: PPI describes pixels in a digital image or on a screen. DPI describes ink dots a printer physically places on paper. A 300 PPI image sent to a 1200 DPI printer produces a print where each image pixel is reproduced using roughly 16 ink dots of different colors. See the full DPI vs PPI breakdown for when the distinction matters.
The PPI Formula
PPI is diagonal pixels divided by diagonal inches. To get the diagonal in pixels, use the Pythagorean theorem on width and height. Written as a single line:
PPI = sqrt(width_px^2 + height_px^2) / diagonal_inches
Worked example for a 27 inch 4K monitor at 3840 by 2160:
- width squared = 3840 x 3840 = 14,745,600
- height squared = 2160 x 2160 = 4,665,600
- sum = 19,411,200
- square root = 4405.8 pixels diagonal
- 4405.8 / 27 = 163.2 PPI
The calculator above runs this math live. If you already know the resolution and physical size, just pick a preset.
PPI on Common Devices
Pixel density for phones, tablets, laptops, monitors, and TVs you probably use. Values are rounded to the nearest whole PPI.
| Device | Resolution | Diagonal | PPI | Class |
|---|---|---|---|---|
| iPhone 16 Pro | 2622 x 1206 | 6.3 in | 460 | Ultra HiDPI, 3x pixel ratio |
| iPhone SE (2022) | 1334 x 750 | 4.7 in | 326 | Baseline Retina |
| Samsung Galaxy S24 | 2340 x 1080 | 6.2 in | 416 | Ultra HiDPI |
| iPad Pro 12.9 | 2732 x 2048 | 12.9 in | 264 | Tablet Retina |
| iPad (10th gen) | 2360 x 1640 | 10.9 in | 264 | Tablet Retina |
| MacBook Pro 14 (2024) | 3024 x 1964 | 14.2 in | 254 | Laptop Retina |
| MacBook Air 13 M3 | 2560 x 1664 | 13.6 in | 224 | Laptop Retina |
| Studio Display 27 | 5120 x 2880 | 27 in | 218 | 5K Retina |
| Dell 27 4K (U2723QE) | 3840 x 2160 | 27 in | 163 | Sharp desktop |
| 24 FHD monitor (typical) | 1920 x 1080 | 24 in | 92 | Web standard baseline |
| 27 1440p monitor | 2560 x 1440 | 27 in | 109 | Standard desktop |
| 55 4K TV (10 ft viewing) | 3840 x 2160 | 55 in | 80 | Low PPI, distance viewing |
PPI Reference Table
Pixels per inch, centimeter, and millimeter at every standard density.
| PPI | Pixels per cm | Pixels per mm | Typical usage |
|---|---|---|---|
| 72 | 28.35 | 2.83 | Legacy Mac screen reference, ignored for most modern workflows |
| 96 | 37.80 | 3.78 | Windows default, CSS reference pixel, web baseline |
| 120 | 47.24 | 4.72 | 125 percent Windows scaling, entry-level HiDPI |
| 144 | 56.69 | 5.67 | 150 percent scaling, common on Surface devices |
| 163 | 64.17 | 6.42 | 27 inch 4K desktop monitor, crisp without scaling |
| 218 | 85.83 | 8.58 | Apple Studio Display 5K, 2x Retina |
| 264 | 103.94 | 10.39 | iPad Pro, iPad Air Retina |
| 326 | 128.35 | 12.83 | Classic iPhone Retina baseline |
| 458 - 460 | 180.31 | 18.03 | iPhone Pro Super Retina XDR |
Retina, HiDPI, and Device Pixel Ratio
Apple coined the term retina in 2010 for displays dense enough that the eye cannot resolve individual pixels at normal viewing distance. The threshold depends on distance: about 300 PPI at 10 inches for a phone, 220 PPI at 20 inches for a laptop, 120 PPI at 4 feet for a TV. Beyond the threshold, more PPI does not produce visibly sharper output.
On the web, the browser exposes this through window.devicePixelRatio. Ratio 1 is a 96 PPI display. Ratio 2 is any 2x Retina device. Ratio 3 is iPhone Pro class. When you serve images, match the ratio: a 100 by 100 CSS pixel image should be 200 by 200 actual pixels on 2x devices and 300 by 300 on 3x, otherwise the image looks soft.
| PPI | Pixel ratio | Notes |
|---|---|---|
| 96 | 1.00x | CSS reference. One CSS pixel equals one device pixel. |
| 120 | 1.25x | Windows 125 percent scaling, most 1080p laptops. |
| 144 | 1.50x | Windows 150 percent, Surface devices. |
| 192 | 2.00x | Retina MacBook, iPad. Use 2x image assets. |
| 288 | 3.00x | iPhone Pro class. Use 3x image assets. |
Pixels Per Inch for Printing
For print, 300 PPI is the professional benchmark for anything viewed at reading distance: photographs, magazines, books, brochures. 150 PPI is acceptable for newspapers, flyers on coarse paper, and posters seen from a few feet. 72 to 96 PPI is enough for banners viewed from 10 feet or more. Billboards seen from across a parking lot can print as low as 25 to 50 PPI.
The rule of thumb: every foot of viewing distance buys you roughly 30 PPI of headroom. A print viewed from 1 foot needs 300 PPI. A print viewed from 10 feet is fine at 30 PPI. Beyond the distance threshold, adding more pixels just wastes file size and RIP time.
To find pixel requirements for a specific print size, use the DPI Calculator or the Image Size Calculator. For the inverse problem (how large a given image can safely print) both tools invert the math automatically.
Related Tools and Guides
Every pixel measurement, formula, and reference you need.
Frequently Asked Questions
PPI is pixel density. It measures how many individual pixels are packed into one linear inch of a screen or image. Higher PPI means smaller, denser pixels and a sharper picture. A 6.1 inch iPhone has 460 PPI. A 24 inch 1080p monitor has about 92 PPI. The first looks razor sharp at 10 inches from your face; the second has visible pixels if you lean in close.
Find the diagonal pixel count with the Pythagorean theorem, then divide by the diagonal screen size in inches. Formula: PPI = sqrt(width squared plus height squared) divided by diagonal in inches. Example: a 2560 by 1440 screen at 27 inches has a diagonal of sqrt(2560 squared plus 1440 squared) = 2938 pixels. 2938 divided by 27 equals 108.8 PPI. Use the calculator at the top of this page to skip the math.
1920 by 1080 is a resolution, not a pixel density. The PPI depends on screen size. On a 24 inch monitor 1920 by 1080 is about 92 PPI. On a 27 inch monitor it drops to 82 PPI. On a 15.6 inch laptop it rises to 141 PPI. Same resolution, different pixel density, because PPI is pixels divided by physical inches.
300 PPI is the professional print standard for photographs, books, and magazines viewed at arm's length. For newspapers and coarser paper, 150 to 200 PPI is fine because the paper cannot hold finer detail. For large posters viewed from a few feet away, 150 PPI is plenty. For billboards viewed from across a parking lot, 25 to 50 PPI works because the eye cannot resolve more at that distance.
Apple's marketing term retina kicks in at roughly 218 PPI for desktops (Studio Display), 224 to 254 PPI for MacBooks, 264 PPI for iPads, and 326 to 460 PPI for iPhones. The underlying definition is pixels so small the eye cannot distinguish them at normal viewing distance. For a phone held 10 inches away that starts around 300 PPI. For a laptop 20 inches away it starts around 150 PPI.
Not exactly. PPI measures pixels on a screen or in an image file. DPI measures ink dots a printer lays on paper. One image pixel printed on a 1200 DPI printer uses roughly 16 ink dots of varied color to reproduce the pixel. Photoshop and most software label this field DPI even when they mean PPI, and the terms are used interchangeably in practice. The useful distinction: PPI is digital, DPI is physical.
441 PPI is a high-end phone pixel density, roughly matching the Galaxy S24 Ultra or similar flagship devices. It is Ultra HiDPI territory: well above the retina threshold of about 300 PPI at 10 inches viewing distance, enough to render 4K video downscaled onto a 6 inch screen without visible pixelation, and enough headroom for VR headsets when magnified by a lens.
Anything above 320 PPI looks sharp on a phone. Most flagships ship between 400 and 500 PPI, which is overkill for flat content but useful for VR passthrough and small text at a glance. The human eye caps out around 300 to 400 PPI at 10 inch viewing distance, so PPI beyond 500 rarely shows visible benefit on a flat screen.
Only up to a point. Above the retina threshold for your viewing distance, higher PPI wastes rendering power and battery life with no visible improvement. A 27 inch 5K monitor at 218 PPI looks identical to an 8K version at 326 PPI to most viewers at normal desk distance. Pay for higher PPI when content is small, close, or magnified (phones, VR). Skip it for TVs, billboards, and large monitors.
You cannot add real detail by raising PPI in software. Changing the PPI metadata in Photoshop just tells a printer to render smaller or larger, the pixel count stays the same. To physically fit more pixels per inch you need the original source at higher resolution, AI upscaling, or rescanning. A 1000 by 1000 image at 300 PPI prints at 3.33 inches; the same file at 600 PPI prints at 1.67 inches with the exact same image data.