How to Use Our PPI Calculator

To calculate the PPI of a display, you need three basic specifications from the manufacturer. The calculator uses the Pythagorean theorem to find the diagonal resolution and divides it by the screen size.

• Horizontal Resolution (Width in Pixels): Enter the number of pixels across the width of the screen. For a standard 4K display, this would be 3840.

• Vertical Resolution (Height in Pixels): Enter the number of pixels from the top to the bottom of the screen. For a 4K display, this is 2160.

• Screen Size (Diagonal): Enter the advertised diagonal size of the screen in inches (e.g., 27″ for a monitor or 6.7″ for a smartphone).

Once you enter these three values, the calculator will instantly provide the screen’s PPI.

Understanding Your Results: What Does PPI Mean?

Your result is a number representing Pixels Per Inch (PPI). This number quantifies the concentration of pixels within a one-inch line on the screen. A higher PPI means more pixels are packed into the same amount of space, resulting in:

• Sharper Text: Characters on the screen have smoother curves and are easier to read.

• Clearer Images: Photos and videos appear more detailed and life-like.

• No Visible Pixels: The “screen door effect” (seeing the grid-like structure of pixels) is eliminated.

In short, a higher PPI generally leads to a higher-quality, more premium-looking display.

The “Retina” Revolution: The Point of Diminishing Returns

The term “Retina Display,” coined by Apple, is not a specific technology but a marketing term for a screen with a PPI so high that the human eye cannot distinguish individual pixels from a typical viewing distance.

This is the crucial takeaway: the “goodness” of a PPI value is directly related to how far away you are from the screen.

• Smartphones: You hold them close, so they need a very high PPI (often 300+) for pixels to be invisible.

• Monitors: You sit farther away, so they can have a lower PPI and still look perfectly sharp.

• TVs: You watch them from across the room, so their PPI can be much lower still.

This is why a 65-inch 4K TV (68 PPI) can look just as sharp as a 13-inch MacBook Pro with a “Retina” display (227 PPI) — you are viewing them from vastly different distances.

PPI Benchmarks: How Do Common Devices Compare?

To give your result some context, here is the approximate PPI for a range of popular devices.

The Math Behind Screen Sharpness

For those interested, the calculator finds the PPI using the following formula derived from the Pythagorean theorem:

$$PPI = \frac{\sqrt{\text{width_pixels}^2 + \text{height_pixels}^2}}{\text{diagonal_size_in_inches}}$$

It first calculates the total number of pixels along the diagonal and then divides that by the diagonal length in inches.

Frequently Asked Questions

What is a good PPI for a smartphone?

For a smartphone, a PPI of 300 or higher is considered excellent. Most modern flagship phones, like those from Apple and Samsung, far exceed this, often landing in the 450-550 PPI range. This high density ensures text and images are exceptionally sharp, even when held close to the face.

What is a good PPI for a computer monitor?

The ideal PPI for a desktop monitor is a subject of debate, but a common sweet spot is between 110 and 160 PPI.

• ~110 PPI: This is typical for a 27-inch 1440p (QHD) monitor. It offers a good balance of sharpness and performance, and UI elements are sized comfortably without scaling.

• ~160 PPI: This is typical for a 27-inch 4K monitor. It provides noticeably sharper text and images, but often requires the operating system to scale up text and icons to keep them readable.

What is a good PPI for a TV?

Because you sit far away from a television, the required PPI is much lower. A 65-inch 4K TV has a PPI of about 68, which is perfectly sharp from a typical viewing distance of 7-10 feet. Worrying about high PPI on a TV is unnecessary; resolution (4K vs. 8K) and viewing distance are far more important factors.

What is the difference between PPI and DPI?

This is a common point of confusion, especially for designers.

• PPI (Pixels Per Inch): Refers to the density of pixels on a digital screen. It is a fixed, physical characteristic of the display hardware.

• DPI (Dots Per Inch): Refers to the density of ink dots on a printed medium. It is a setting used when printing an image to determine its physical size and print quality.

While often used interchangeably in casual conversation, they describe two different domains: PPI is for screens, and DPI is for print.

Is PPI more important than resolution?

They are two sides of the same coin. Resolution tells you the total number of pixels, while PPI tells you how concentrated those pixels are. For example, a 32-inch 4K monitor and a 24-inch 4K monitor have the exact same resolution (3840 x 2160), but the 24-inch monitor will have a much higher PPI and therefore look significantly sharper because the same number of pixels are squeezed into a smaller area. Neither is “more important”—they work together to define screen quality.

What is a “Retina” display and what is its PPI?

There is no single PPI value for a “Retina” display. The term refers to any screen where the pixel density is high enough to make pixels invisible at its typical viewing distance.

• An iPhone might need ~326+ PPI to be called Retina because it’s held close.

• An iPad might need ~264+ PPI.

• A MacBook might need ~220+ PPI because it’s viewed from farther away.

It’s a “floating” target based on how you use the device.

Can the human eye see more than 300 PPI?

Yes, but it depends entirely on distance. If you press your face right up against a 300 PPI screen, you will absolutely see the pixels. The 300 PPI benchmark, popularized by Apple’s original Retina iPhone, was based on a typical viewing distance of about 10-12 inches. From that distance, 300 PPI is roughly the point where the pixels “disappear.”

How does PPI relate to 1080p, 1440p, and 4K?

These terms refer to common screen resolutions, which are a key component of the PPI calculation.

• 1080p (Full HD): 1920 x 1080 pixels

• 1440p (QHD): 2560 x 1440 pixels

• 4K (UHD): 3840 x 2160 pixels

On a screen of the same size, 4K will always have a higher PPI than 1440p, and 1440p will always have a higher PPI than 1080p.

Concrete Example (27-inch monitor):

• A 27″ 1080p monitor has 81 PPI. (Often considered blurry for this size)

• A 27″ 1440p monitor has 109 PPI. (The popular “sweet spot”)

• A 27″ 4K monitor has 163 PPI. (Very sharp, requires scaling)

Does a higher PPI use more battery?

Yes, indirectly. A higher PPI screen usually means a higher resolution screen. Lighting up more pixels requires more processing power from the graphics chip (GPU) and more power for the screen’s backlight. As a result, a 4K screen on a laptop will almost always consume more battery than a 1080p screen on the same device, all else being equal.

How do I find the resolution and screen size of my device?

• Screen Size: This is the advertised diagonal measurement (e.g., 6.1″ for an iPhone 15, 27″ for a monitor). This is usually listed on the product box or the manufacturer’s website.

• Resolution:

  • Windows: Right-click the desktop > Display settings. Your resolution will be listed under “Display resolution.”

  • macOS: Click the Apple menu > About This Mac > Displays.

  • For any device: The quickest way is often to Google your exact model name + “resolution” (e.g., “Dell U2723QE resolution”).

Continue Your Tech Calculations

Understanding PPI is a key part of evaluating screen quality. You might also find these tools helpful in setting up your displays.

• Use our TV Viewing Distance Calculator to see how PPI and viewing distance work together for large screens.

• Calculate a screen’s width and height with our Aspect Ratio Calculator.