PPI Calculator

A PPI calculator helps you find a display’s pixels per inch, a measure of how densely pixels are packed into a screen. Higher PPI generally means sharper text, crisper images, and less visible pixel structure at normal viewing distances. This tool is useful for monitors, laptops, smartphones, tablets, TVs, cameras, and any device where screen sharpness matters.

On this page, the calculator is designed to determine PPI from a device’s screen size and resolution. In practice, that means you enter the physical diagonal size of the display and its pixel dimensions, then the tool computes the screen density for you.

Step-by-step instructions

1. Find the screen size
   Measure or look up the diagonal screen size in inches. This is usually the advertised size, such as 24 inches, 13.3 inches, or 6.7 inches.

2. Enter the horizontal pixel count
   Input the display’s width in pixels. Common examples include 1920, 2560, 3840, or 1080 depending on the device.

3. Enter the vertical pixel count
   Input the display’s height in pixels, such as 1080, 1440, or 2160.

4. Run the calculation
   The tool uses the screen’s diagonal pixel count and divides it by the diagonal size in inches to produce PPI.

5. Review the result
   The output tells you how many pixels fit into one inch of the display. You can use this number to compare screens of different sizes and resolutions.

Tips for accurate results

• Use the native resolution of the display, not a scaled software setting.
• Make sure the screen size is the diagonal measurement in inches, not width or height.
• If you are comparing two devices, compare their PPI values rather than resolution alone.
• Remember that PPI is about pixel density, not brightness, color quality, or refresh rate.
• For the most meaningful comparison, consider both PPI and viewing distance. A lower-PPI large monitor may still look sharp from farther away.

Best practices

• Use the calculator when shopping for a monitor or phone to estimate how sharp text and images will appear.
• Check PPI before choosing wallpaper, graphic assets, or UI design targets.
• If a device lists multiple display modes, calculate PPI using the mode you plan to use most often.
• For close-up use, such as phones and tablets, higher PPI is usually more noticeable than it is on large TVs.

In short, the calculator makes it easy to turn raw resolution numbers into a practical sharpness metric. Enter the size and pixel dimensions, then use the PPI result to compare displays with confidence.

Pixels per inch, or PPI, describes how many pixels are packed into one inch of a display. It is a common way to measure screen sharpness. Two screens can have the same resolution but very different PPI if one is larger than the other. That is why PPI is often more useful than resolution alone when comparing devices.

A high PPI usually means finer detail, smoother text edges, and less visible pixelation. A lower PPI can still look fine at a distance, especially on larger screens, but up close you may notice individual pixels more easily.

The formula

The standard PPI formula uses the display’s diagonal pixel count and diagonal size in inches:

PPI = √(px_w² + px_h²) / d

Where:

• px_w = horizontal pixel count of the display, in pixels
• px_h = vertical pixel count of the display, in pixels
• d = screen size measured diagonally, in inches
• √(px_w² + px_h²) = diagonal pixel count, found using the Pythagorean theorem

This formula works because screen resolution is usually given as width × height, while screen size is given as a diagonal measurement.

Worked examples

Example 1: 1920 × 1080 on a 24-inch monitor

1. Find the diagonal pixel count:

   • √(1920² + 1080²)
   • √(3,686,400 + 1,166,400)
   • √4,852,800
   • 2202.91 pixels

2. Divide by screen size:

   • 2202.91 ÷ 24 = 91.79 PPI

So a 24-inch 1080p monitor has about 91.8 PPI.

Example 2: 2560 × 1440 on a 27-inch monitor

1. Diagonal pixel count:

   • √(2560² + 1440²)
   • √(6,553,600 + 2,073,600)
   • √8,627,200
   • 2937.21 pixels

2. PPI:

   • 2937.21 ÷ 27 = 108.79 PPI

So a 27-inch QHD monitor has about 108.8 PPI.

Example 3: 3840 × 2160 on a 27-inch monitor

1. Diagonal pixel count:

   • √(3840² + 2160²)
   • √(14,745,600 + 4,665,600)
   • √19,411,200
   • 4405.81 pixels

2. PPI:

   • 4405.81 ÷ 27 = 163.18 PPI

So a 27-inch 4K monitor has about 163.2 PPI.

Example 4: 1170 × 2532 on a 6.1-inch phone

1. Diagonal pixel count:

   • √(1170² + 2532²)
   • √(1,368,900 + 6,411,024)
   • √7,779,924
   • 2789.25 pixels

2. PPI:

   • 2789.25 ÷ 6.1 = 457.25 PPI

So a 6.1-inch smartphone at that resolution has about 457.3 PPI.

Example 5: 1366 × 768 on a 15.6-inch laptop

1. Diagonal pixel count:

   • √(1366² + 768²)
   • √(1,865,956 + 589,824)
   • √2,455,780
   • 1566.78 pixels

2. PPI:

   • 1566.78 ÷ 15.6 = 100.43 PPI

So a 15.6-inch 1366×768 panel has about 100.4 PPI.

When to use PPI

Use PPI when you want to compare displays of different sizes fairly. Resolution alone can be misleading. For example, a 4K TV and a 4K monitor may share the same pixel count, but the larger TV has lower PPI because the pixels are spread over a bigger area.

PPI is especially helpful when:

• buying a monitor or laptop
• comparing phones and tablets
• planning UI and graphic design assets
• estimating how sharp a screen will look at a given distance
• choosing between resolution and screen size trade-offs

Why PPI matters

The human eye notices detail differently depending on viewing distance. A very high PPI phone looks extremely sharp because it is held close. A large monitor can have lower PPI and still appear crisp because it is viewed farther away. That is why PPI should be understood as one part of the whole viewing experience, not the only factor.

In short, PPI turns resolution and size into a practical sharpness measure. If you know the pixel dimensions and diagonal size, you can calculate a meaningful number that helps compare almost any display.