PPI Calculator
Calculate pixels per inch (PPI) for any display. PPI measures the pixel density of a screen — how many pixels are packed into each inch of display. Higher PPI means sharper text and images. Enter your screen resolution and diagonal size to find the PPI, dot pitch, and total pixel count. Also see our Pixels to Inches and Image Resolution Converter.
Related Calculators:
How to Calculate PPI
Formula:
PPI = √(width² + height²) ÷ diagonal (inches)
Dot Pitch (mm) = 25.4 ÷ PPI
First calculate the diagonal resolution in pixels using the Pythagorean theorem, then divide by the physical diagonal size in inches. The dot pitch is the physical distance between pixel centers, calculated by dividing 25.4 mm (1 inch) by the PPI.
PPI Reference Table
| Device | Resolution | Size | PPI |
|---|---|---|---|
| iPhone 15 Pro | 2556×1179 | 6.1" | 460 |
| MacBook Pro 14" | 3024×1964 | 14.2" | 254 |
| iMac 24" | 4480×2520 | 23.5" | 218 |
| 4K Monitor 27" | 3840×2160 | 27" | 163 |
| 1080p Monitor 24" | 1920×1080 | 24" | 92 |
| 1440p Monitor 27" | 2560×1440 | 27" | 109 |
| 4K TV 55" | 3840×2160 | 55" | 80 |
| iPad Pro 12.9" | 2732×2048 | 12.9" | 264 |
What is a Good PPI?
- 300+ PPI: Print quality — individual pixels invisible at any distance (smartphones, Retina displays)
- 200-300 PPI: Excellent — sharp at arm's length (tablets, laptop Retina screens)
- 100-200 PPI: Good — standard desktop monitors at normal viewing distance
- 70-100 PPI: Acceptable — large TVs viewed from couch distance
- Below 70 PPI: Low — pixels visible, suitable only for large displays viewed from far away
Frequently Asked Questions
What is the difference between PPI and DPI?
PPI (pixels per inch) refers to screen displays — how many pixels per inch on a monitor. DPI (dots per inch) refers to printing — how many ink dots per inch a printer produces. They are often used interchangeably but technically measure different things.
What PPI is Retina display?
Apple defines "Retina" as a display where individual pixels cannot be distinguished at a typical viewing distance. For iPhones this is 326+ PPI, for iPads 264 PPI, and for MacBooks 218-254 PPI (because they are viewed from farther away).
Does higher PPI mean better quality?
Yes, up to a point. Higher PPI means sharper text and images. However, beyond what your eyes can distinguish at your viewing distance, additional PPI provides no visible benefit. For a 27" desktop monitor at arm's length, 110+ PPI looks sharp to most people.
What is dot pitch?
Dot pitch is the physical distance (in mm) between the centers of adjacent pixels. Lower dot pitch = higher pixel density = sharper image. A 0.25mm dot pitch equals about 100 PPI.
What is the retina display threshold distance?
The human eye can distinguish individual pixels when the angular size exceeds about 1 arcminute. The formula for maximum viewing distance where pixels become invisible is: Distance (inches) = 3438 ÷ PPI. For a 110 PPI monitor, pixels disappear at about 31 inches. For a 326 PPI phone, pixels are invisible at just 10.5 inches. For VR headsets (20+ PPI at perceived distance), the "screen door effect" is visible because the display is so close to your eyes.
Why does higher PPI matter for VR headsets?
VR headsets place displays just 1-2 inches from your eyes, magnified by lenses to fill your field of view. This means you need extremely high PPI (1000+) to eliminate the visible pixel grid ("screen door effect"). Current VR headsets achieve 20-35 pixels per degree (PPD), but 60+ PPD is needed to match human visual acuity. The Meta Quest 3 has about 25 PPD, while the Apple Vision Pro achieves about 34 PPD.
What is the optimal viewing distance formula?
The optimal viewing distance depends on both screen size and resolution. The minimum distance where pixels are invisible: D = screen_diagonal × PPI ÷ 3438. For comfortable viewing of the full screen: recommended distance = 1.5× to 2.5× the screen diagonal. For a 27" 4K monitor (163 PPI): min distance = 21" (pixels invisible), recommended = 27-40" for comfort. For a 65" 4K TV (68 PPI): min distance = 51", recommended = 8-10 feet.
Common Device PPI Values
Pixel density comparison across popular devices, monitors at various resolutions and sizes:
| Device / Monitor | Resolution | Size | PPI | Category |
|---|---|---|---|---|
| iPhone 15 Pro Max | 2796×1290 | 6.7" | 460 | Phone |
| iPhone 15 Pro | 2556×1179 | 6.1" | 460 | Phone |
| Samsung Galaxy S24 Ultra | 3120×1440 | 6.8" | 505 | Phone |
| Google Pixel 8 Pro | 2992×1344 | 6.7" | 489 | Phone |
| iPad Pro 11" | 2388×1668 | 11" | 264 | Tablet |
| iPad Pro 12.9" | 2732×2048 | 12.9" | 264 | Tablet |
| MacBook Air 13" (M2) | 2560×1664 | 13.6" | 224 | Laptop |
| MacBook Pro 14" | 3024×1964 | 14.2" | 254 | Laptop |
| MacBook Pro 16" | 3456×2234 | 16.2" | 254 | Laptop |
| 1080p @ 24" | 1920×1080 | 24" | 92 | Monitor |
| 1080p @ 27" | 1920×1080 | 27" | 82 | Monitor |
| 1440p @ 27" | 2560×1440 | 27" | 109 | Monitor |
| 1440p @ 32" | 2560×1440 | 32" | 92 | Monitor |
| 4K @ 24" | 3840×2160 | 24" | 184 | Monitor |
| 4K @ 27" | 3840×2160 | 27" | 163 | Monitor |
| 4K @ 32" | 3840×2160 | 32" | 138 | Monitor |
| 5K @ 27" (Apple Studio) | 5120×2880 | 27" | 218 | Monitor |
| Ultrawide 3440×1440 @ 34" | 3440×1440 | 34" | 109 | Monitor |
Worked Examples
Example 1: Calculate PPI for a 27" 4K Monitor
Given: Resolution = 3840×2160, Diagonal = 27 inches
Step 1: Diagonal pixels = √(3840² + 2160²) = √(14,745,600 + 4,665,600) = √19,411,200 = 4,406.0 px
Step 2: PPI = 4,406.0 ÷ 27 = 163.2 PPI
Step 3: Dot pitch = 25.4 ÷ 163.2 = 0.1556 mm
At this PPI, text appears sharp at the typical 24-28" viewing distance for a desk monitor.
Example 2: Comparing Phone Screens — iPhone 15 Pro vs Samsung Galaxy S24 Ultra
iPhone 15 Pro: 2556×1179, 6.1" → √(2556² + 1179²) = √(6,533,136 + 1,390,041) = √7,923,177 = 2,814.8 → 2,814.8 ÷ 6.1 = 461 PPI
Samsung Galaxy S24 Ultra: 3120×1440, 6.8" → √(3120² + 1440²) = √(9,734,400 + 2,073,600) = √11,808,000 = 3,436.6 → 3,436.6 ÷ 6.8 = 505 PPI
The Samsung has 10% higher pixel density. However, both are well above the ~300 PPI threshold where pixels become invisible to the naked eye at normal phone viewing distance (10-14 inches), so the difference is imperceptible in daily use.
Example 3: Print Resolution — What PPI is Needed for 300 DPI Print?
Scenario: You want to print a photo at 8×10 inches at professional quality (300 DPI).
Required pixels: 8 × 300 = 2,400 px wide, 10 × 300 = 3,000 px tall
Total pixels needed: 2,400 × 3,000 = 7,200,000 pixels = 7.2 megapixels minimum
For poster size (24×36 at 150 DPI): 24 × 150 = 3,600 px × 36 × 150 = 5,400 px = 19.4 MP
Note: Print DPI and screen PPI are different concepts. A 300 DPI print is considered professional/magazine quality. 150 DPI is acceptable for posters viewed from 2+ feet away.
PPI vs DPI — Screen Pixels vs Print Dots
PPI (Pixels Per Inch) measures the pixel density of a digital screen. Each pixel is a single point of light that can display any color. A 163 PPI monitor has 163 individual light-emitting pixels in each linear inch of its display.
DPI (Dots Per Inch) measures the ink dot density produced by a printer. Printers create colors by overlaying tiny dots of ink (typically CMYK — cyan, magenta, yellow, black). A 1200 DPI printer places 1,200 individual ink dots per linear inch.
Key differences:
- One pixel = one color point (can be any color). One print dot = one tiny ink spot (single color — C, M, Y, or K).
- It takes multiple print dots to reproduce one pixel's color information. A 300 PPI image printed at 1200 DPI means each pixel is reproduced by a 4×4 grid of ink dots.
- For print: 300 PPI source image → excellent quality at any DPI. The printer's DPI determines color accuracy, not sharpness.
- For screens: PPI is all that matters — there are no "dots." Higher PPI = sharper display.
When web/graphic designers say "72 DPI" or "96 DPI" for screen images, they actually mean PPI. The confusion arose because early Mac displays were 72 PPI and early Windows displays were 96 PPI, and the terms became incorrectly interchangeable.
Screen Resolution and Clarity
Screen clarity depends on three factors working together: resolution (total pixel count), screen size, and viewing distance. The same resolution looks dramatically different on different screen sizes:
- 1920×1080 (Full HD): Looks sharp on a 24" monitor (92 PPI) at arm's length, but pixelated on a 32" monitor (69 PPI) at the same distance. On a 6" phone at reading distance, it would look very sharp (367 PPI).
- 2560×1440 (QHD/2K): The sweet spot for 27" monitors (109 PPI). Good balance of sharpness and GPU performance for gaming.
- 3840×2160 (4K/UHD): Excellent at 27-32" for productivity (sharp text without scaling issues). On a 55" TV, it delivers 80 PPI — perfect for typical couch viewing distance (6-10 feet).
- 5120×2880 (5K): Designed specifically for 27" displays to achieve 218 PPI (true Retina quality at desk distance). Used in Apple Studio Display and iMac.
Scaling and effective resolution: Modern operating systems use display scaling. A 4K (3840×2160) monitor at 200% scaling renders UI elements as if it were 1920×1080 — but with 4× the pixel detail for ultra-sharp text and icons. macOS defaults to this behavior on Retina displays. Windows calls this "display scaling" and recommends 150% for 4K at 27".
The angular resolution rule: What matters for perceived sharpness is pixels per degree of vision (PPD). The formula: PPD = PPI × viewing_distance_inches × π ÷ 180. Human visual acuity limit is about 60 PPD. A 27" 4K monitor at 24" provides: 163 × 24 × 0.01745 = 68 PPD — exceeding the retina threshold.