27-inch 4K UHD display
A 3840 × 2160 resolution has about 4,405.81 pixels along its diagonal. Divide by 27 inches to get about 163.18 PPI. Its estimated active area is 23.53 × 13.24 inches.
Screen resolution and size
Measure the active display corner to corner, excluding the frame. Changing units converts the current diagonal.
Try a common display
Pixel density
Pixels per inch
163.18 PPI
8.294 megapixels · 0.1557 mm pixel pitch
| Measurement | Width × height |
|---|---|
| Inches | 23.53 × 13.24 in |
| Centimeters | 59.77 × 33.62 cm |
| Diagonal pixels | 4,405.81 |
PPI = √(width² + height²) ÷ diagonal in inches. Assumes a flat, rectangular active area and square pixels. Rounded manufacturer sizes make the result approximate.
Calculations stay in your browser. Presets are example size and resolution combinations, not product recommendations.
How to use the PPI Calculator
- 01
Enter the horizontal and vertical pixel counts from the display’s native resolution.
- 02
Enter the diagonal of the active screen, excluding its bezel. Choose inches, centimeters, or millimeters.
- 03
Read the PPI result, physical dimensions, and pixel pitch. Use the presets to compare common monitor specifications.
Examples
Same pixels, larger display
At 32 inches, the same 3840 × 2160 resolution gives about 137.68 PPI. Spreading the same pixel count across more physical space makes each pixel larger.
Measure in centimeters
A 68.58 cm diagonal equals 27 inches. Select centimeters to enter that size directly; changing the unit converts the current diagonal instead of merely relabeling it.
How PPI is calculated
First use the Pythagorean theorem to find the pixel diagonal: √(horizontal pixels² + vertical pixels²). Divide that by the physical diagonal in inches. Width and height are then proportional to their pixel counts. The calculation assumes square pixels on a flat rectangular active area. One inch equals exactly 2.54 centimeters.
Pixel pitch and physical dimensions
Pixel pitch is the center-to-center distance between neighboring pixels. For square pixels, pitch in millimeters is 25.4 ÷ PPI. A 100 PPI display has a pitch of 0.254 mm. The estimated physical width and height exclude bezels, stands, and other hardware, so they should not be used as the product’s outside dimensions.
PPI, resolution, and interface scaling
Resolution counts pixels; PPI describes how closely they are packed. A higher PPI value can display more detail per inch, but the result does not rate brightness, contrast, color, viewing comfort, or panel quality. Operating system scaling changes interface size in logical units without changing the physical panel’s PPI. Use the native hardware resolution for this calculation.
What to know
- Assumes square pixels and a flat rectangular display. Results depend on the accuracy of the active diagonal size.
- The diagram shows proportions, not actual physical size. Resolution is limited to 1,000,000 pixels per side.
Common questions
Is PPI the same as DPI?
PPI counts image or screen pixels per inch. DPI generally describes output dots, such as those produced by a printer. The terms are sometimes used loosely, but this calculator measures display pixel density.
Should I include the screen’s frame in the diagonal?
No. Use the visible active screen diagonal. Including the bezel makes the diagonal too large and the calculated PPI too low.
Does rotating the display change PPI?
No. Swapping width and height leaves both diagonal pixel count and physical diagonal unchanged. The calculated physical width and height swap places.
Why is my result slightly different from a manufacturer’s specification?
Advertised diagonal sizes may be rounded. An exact active-area measurement can give a slightly different result. Non-square pixels or curved display measurements also fall outside the simple flat-screen model.