Pixels Per Inch - PPI, Dot Pitch, and Pixel Density

Pixels per inch (PPI) is the single number that tells you how densely packed the pixels are on any screen. The calculator below takes a display's horizontal resolution, vertical resolution, and diagonal size in inches, returns PPI from the Pythagorean formula, and reports dot pitch, pixel size, and total pixel count in the same step.

• • Comparing monitors and laptops: Enter the native resolution and diagonal of any display to read off the PPI and compare a 27-inch 4K panel to a 32-inch 1440p panel.
• • Checking a phone or tablet: Plug in the resolution and diagonal to confirm whether the manufacturer is quoting PPI or marketing density, and read the dot pitch in millimeters.
• • Sizing print at the right PPI: Convert a pixel count into a real-world print size at a known PPI, or work backwards from a target print size to find the pixel count you need.
• • Diagnosing a TV or projector: Confirm the diagonal PPI is in the typical 40 to 80 range and decide whether a closer seating distance is worth the upgrade.

PPI is calculated from the pixel count, not the panel technology, so the calculator works for LCD, OLED, micro-LED, and projector setups the same way. The result is the diagonal density, the conventional way to compare displays with different aspect ratios side by side.

If you need the inverse direction, turning a pixel count into a physical print or screen size at a known PPI, our pixels to inches calculator handles that conversion in the same pixels-and-inches family.

The calculator reads the horizontal resolution, vertical resolution, and diagonal screen size, computes the diagonal pixel count with the Pythagorean theorem, divides by the diagonal in inches, and surfaces dot pitch, pixel size, and total pixel count.

• widthPx: Horizontal pixel count, e.g. 1920, 2560, or 3840. Use the native resolution.
• heightPx: Vertical pixel count, e.g. 1080, 1440, or 2160. Use the native resolution.
• diagonalIn: Physical diagonal of the screen in inches (e.g. 6.1 phone, 13.3 laptop, 24 monitor, 55 TV).

If you only know a target PPI and want the matching diagonal, divide the diagonal pixel count by your target PPI to read the diagonal in inches. The calculator below does the forward direction in a single step.

According to Omni Calculator Pixels per inch, pixels per inch (PPI) equals the square root of (width in pixels squared plus height in pixels squared) divided by the diagonal in inches, yielding about 95.78 PPI for a 23-inch 1920x1080 monitor.

According to Wikipedia: Pixel density, pixel density is measured in PPI and equals diagonal resolution in pixels divided by diagonal screen size in inches, with higher PPI values indicating a sharper image at a given viewing distance.

For the broader display math (aspect ratio, total pixels, viewing distance) at the same time, the screen resolution calculator takes the same resolution and diagonal inputs and adds those outputs alongside the PPI.

Four small ideas explain every number the calculator returns.

Once you know a display's PPI you can plan viewing distance, dot pitch comparisons, and pixel-density class without re-doing the math.

For the matching aspect-ratio math that goes with PPI when you compare a 16:9 monitor to a 21:9 ultrawide, our CSS aspect ratio calculator takes the same width and height pair and returns the ratio in the format CSS, video, and print specs use.

Five short steps are enough to get a complete PPI reading for any monitor, laptop, phone, or TV.

1. 1 Enter the native resolution: Type the horizontal and vertical pixel counts (1920 x 1080 for full-HD or 3840 x 2160 for 4K). Use the native resolution, not the scaled Windows or macOS resolution.
2. 2 Enter the diagonal size: Type the physical diagonal in inches (6.1 phone, 13.3 laptop, 24 or 27 monitor, 55 TV). The spec sheet lists the same number.
3. 3 Pick a preset if needed: Use the Quick Preset dropdown to auto-fill the three fields with common sizes, then tweak the diagonal if your screen differs.
4. 4 Read the PPI and the dot pitch: The primary result is the PPI in the top black panel, the diagonal pixel density you compare monitors with. The dot pitch row shows the same result in millimeters (0.156 mm on a 27-inch 4K panel is typical).
5. 5 Reset or reuse for the next screen: Hit Reset to restore the default 1920 x 1080 at 24 inches, or change one field at a time to compare a chain of displays.

For a 27-inch 4K monitor, type 3840, 2160, and 27. The calculator returns PPI 163.2, dot pitch 0.156 mm, and total pixels 8,294,400. Swap to a 55-inch 4K TV (3840, 2160, 55) and PPI drops to 80.1 with dot pitch 0.317 mm.

If you need to take a pixel count from the result panel and turn it into CSS-friendly em or rem units for a web layout, the pixel to EM REM converter handles that direction of the same pixel-density family.

A focused calculator turns three well-known spec-sheet numbers into a single comparable PPI plus its companion metrics.

• • Computes PPI from any resolution and diagonal: Accepts any horizontal and vertical pixel count plus a diagonal in inches, so the same tool works for phones, laptops, monitors, TVs, and projectors.
• • Surfaces dot pitch in millimeters: Returns dot pitch alongside PPI using the 25.4 mm per inch conversion factor, the spec monitor and projector reviews use when they quote pixel sharpness.
• • Reports total pixel count and PPCM: Lists total pixel count and the metric PPCM (pixels per centimeter) so you can compare displays that quote density in either system.
• • Includes common display presets: Auto-fills the three inputs for eight common displays so you can compare a candidate screen to a familiar reference in seconds.

When you also need to translate the total pixel count into the actual file size a candidate image will need at a given color depth, the data storage converter handles the byte math so you can plan storage costs alongside the PPI.

Three variables drive what the calculator reports, and two limitations tell you when to interpret the result carefully.

• • PPI is a geometric calculation and does not account for subpixel layout, panel technology, or anti-aliasing. Two displays with the same PPI can still look different if one is OLED with a PenTile layout and the other is RGB-stripe LCD.
• • PPI values above about 600 cross into micro-display territory (VR, head-up, near-eye displays) where the eye can resolve individual pixels at short distances and the perceived sharpness gains flatten out.

The Wikipedia inch page confirms the exact 25.4 mm per inch factor the dot-pitch row uses.

According to Wikipedia: Inch, one inch is exactly 25.4 millimeters, so dot pitch in millimeters equals 25.4 divided by PPI.

To plan the bandwidth the resulting image will need at typical home connections, our upload time calculator estimates the upload time from the file size and your connection speed.