What is dot pitch on a display?

Dot pitch is the diagonal distance in millimeters between the centers of two adjacent pixels on a screen. A smaller dot pitch means pixels are closer together, which results in a sharper image. Dot pitch = (diagonal in inches / diagonal in pixels) × 25.4 mm.

How do I find the aspect ratio of a screen?

To find the aspect ratio, divide the width and height in pixels by their greatest common factor. For example, a 1920 x 1080 screen has a GCF of 120. Dividing both by 120 gives 16:9, which is the aspect ratio.

PPI Calculator | Pixels Per Inch & Screen Resolution Tool

PPI Calculator: Pixels Per Inch

Q: What is a good PPI for a phone screen?

A good PPI for a smartphone screen is generally 300 PPI or higher. At 300 PPI or above, individual pixels are not visible to the naked eye at normal viewing distances, which Apple refers to as Retina display density. Many modern flagship phones exceed 400 PPI.

Calculate pixel density (PPI), dot pitch, megapixels, aspect ratio, and diagonal resolution for any screen. Compare two displays side by side.

📺 Screen PPI Calculator

diagonal_px = √(width² + height²) | PPI = diagonal_px / diagonal_in | Dot Pitch = (diagonal_in / diagonal_px) × 25.4

Width (pixels)

Height (pixels)

Diagonal Unit

Diagonal (inches)

🖥️ Compare Two Screens

Screen A

Width (px)

Height (px)

Diagonal Unit

Diagonal (inches)

Screen B

Width (px)

Height (px)

Diagonal Unit

Diagonal (inches)

Common Screen PPI Reference Chart

Device / Resolution	Screen Size	PPI	Aspect Ratio	Sharpness
iPhone 16 Pro (2868×1320)	6.3 in	460	19.5:9	Retina
Samsung Galaxy S24 (2340×1080)	6.2 in	416	19.5:9	Retina
iPad Pro 13″ (2752×2064)	13 in	264	4:3	Retina
MacBook Pro 14″ (3024×1964)	14.2 in	254	16:10	Retina
4K Monitor (3840×2160)	27 in	163	16:9	Sharp
1440p Monitor (2560×1440)	27 in	109	16:9	Good
1080p Monitor (1920×1080)	27 in	82	16:9	Standard
Full HD TV (1920×1080)	55 in	40	16:9	TV Dist.

How to Calculate Pixels Per Inch (PPI)

PPI calculation tells you the pixel density of any display, measuring how many pixels are packed into one linear inch of screen. A higher PPI always means a sharper, more detailed image.

Step One: Find the Diagonal Pixel Count

Use the Pythagorean theorem to calculate the diagonal length of the screen in pixels. This is needed because screen diagonals are measured in inches, not horizontal or vertical pixels alone.

diagonal_px = √(width_px² + height_px²)

Step Two: Divide by the Physical Diagonal

Divide the diagonal pixel count by the physical diagonal screen size in inches. The result is the PPI value.

PPI = diagonal_px / diagonal_inches

Worked Example: 1920×1080 at 24 inches

Step 1: diagonal_px = √(1920² + 1080²) = √(3,686,400 + 1,166,400) = √4,852,800 ≈ 2202.91 px

Step 2: PPI = 2202.91 / 24 ≈ 91.79 PPI

Step 3: PPI² = 91.79² ≈ 8,425 pixels per square inch

Quick tip: The same PPI value applies to any horizontal, vertical, or diagonal inch on the screen because display pixels are perfectly square.

What Is PPI and Why Does It Matter?

PPI (pixels per inch) is the standard measure of screen sharpness used by display engineers, graphic designers, and everyday consumers choosing between devices. Understanding PPI helps you pick the right monitor, phone, or TV for your needs.

The Retina Display Threshold

Apple coined the term “Retina display” to describe screens where individual pixels are not distinguishable by the human eye at typical viewing distances. For smartphones held about 10 to 12 inches away, the threshold is roughly 300 PPI. For monitors viewed at arm’s length, around 200 PPI is generally sufficient.

PPI and Viewing Distance

What matters is not the raw PPI number alone but PPI relative to viewing distance. A large TV with 40 PPI looks sharp when you sit 8 feet away, but a laptop with 100 PPI would appear blurry at that same distance because you expect to view it much closer. Always consider how far you sit from a screen when evaluating its PPI.

PPI vs. Resolution

Resolution describes the total number of pixels (e.g., 1920×1080). PPI tells you how densely those pixels are packed. Two screens can share the same resolution but have very different PPI values depending on their physical sizes. A 27-inch 1080p monitor has 82 PPI while a 13-inch 1080p laptop has 169 PPI, even though both display the same pixel count.

Dot Pitch: What It Is and How to Calculate It

Dot pitch is the physical distance in millimeters between the centers of two adjacent pixels. Dot pitch calculation is essentially the inverse of PPI: smaller dot pitch means higher pixel density and a sharper image.

Dot Pitch (mm) = (diagonal_inches / diagonal_px) × 25.4

Worked Example: Dot Pitch

A 27-inch 4K monitor (3840×2160) has a diagonal of √(3840² + 2160²) ≈ 4405.8 pixels.

Dot Pitch = (27 / 4405.8) × 25.4 ≈ 0.1557 mm

Professional monitors for medical imaging and precision design work often specify dot pitch directly. Consumer monitors typically advertise PPI instead.

How to Find the Aspect Ratio of a Screen

Aspect ratio calculation reduces the width-to-height pixel relationship to its simplest form. It tells you the proportional shape of a screen independent of its size or resolution.

Using the Greatest Common Factor

Find the GCF of the width and height in pixels. Divide both numbers by the GCF to get the simplified ratio. For 1920×1080, the GCF is 120. Dividing gives 16:9, the standard widescreen ratio used by most modern monitors and televisions.

Common Aspect Ratios and Their Uses

The 16:9 ratio is standard for video, gaming, and most consumer monitors. The 16:10 ratio is common on laptops and offers slightly more vertical space for productivity. The 4:3 ratio was the standard for older televisions and monitors and is still used on many tablets. Ultrawide monitors use 21:9 for immersive cinema and multi-window workflows.

Frequently Asked Questions

PPI stands for pixels per inch and measures how many pixels fit in a one-inch line on a display. A higher PPI means more pixels are packed into the same physical space, producing a sharper and more detailed image visible at close range.

To calculate PPI, first find the diagonal pixel count using the Pythagorean theorem: diagonal = √(width² + height²). Then divide the diagonal pixel count by the physical screen diagonal in inches: PPI = diagonal pixels / diagonal inches.

A good PPI for a smartphone is generally 300 PPI or higher. At 300 PPI or above, individual pixels are not visible to the naked eye at normal viewing distances. Many modern flagship phones exceed 400 PPI for extremely sharp text and imagery.

PPI (pixels per inch) refers to the pixel density of a digital screen. DPI (dots per inch) refers to the ink dot density of a physical print or the sensitivity setting of a mouse or scanner. They are often used interchangeably in casual conversation but technically describe different media.

Dot pitch is the diagonal distance in millimeters between the centers of two adjacent pixels. A smaller dot pitch means pixels are closer together, resulting in a sharper image. The formula is: Dot Pitch = (diagonal inches / diagonal pixels) × 25.4 mm.

A good PPI for a desktop monitor is typically 90 to 110 PPI for standard displays viewed at arm’s length. A 4K monitor at 27 inches reaches around 163 PPI. For design, photo editing, and detailed work, monitors above 120 PPI offer noticeably sharper detail.

To find the aspect ratio, divide the width and height pixel values by their greatest common factor (GCF). For a 1920×1080 screen, the GCF is 120. Dividing both by 120 gives 16:9, which is the aspect ratio in its simplest form.

Pixels per square inch (PPI²) is the number of pixels in a one-inch by one-inch area of a screen. It equals PPI multiplied by PPI. A screen with 300 PPI contains exactly 90,000 pixels in every square inch of its display surface.