Know the display behind the pixels
Screen PPI calculator
Enter the screen’s native pixel resolution and diagonal size to find its physical pixel density. No device detection or assumed screen size.
Need the physical size of an image displayed at this density? Copy the PPI, open the pixels to inches converter, choose “A physical screen,” and enter the value. That conversion describes device pixels at native size; application scaling can change how large an image appears.
How to calculate screen PPI
Screen size is usually given along a diagonal, while resolution gives horizontal and vertical pixel counts. For a rectangular screen with square pixels, the Pythagorean theorem puts those measurements on the same axis:
A 2,560 × 1,440 display has about 2,937.21 pixels along its diagonal. If that diagonal is exactly 27 inches, dividing by 27 gives about 108.79 PPI. A centimeter measurement is divided by 2.54 before using this formula.
What pixel pitch and physical size tell you
Pixel pitch here means the distance between corresponding points in neighboring pixels. It is the reciprocal of density, expressed in millimeters: pitch = 25.4 ÷ PPI. At 100 PPI, one pixel step spans 0.254 mm. This is the full pixel spacing, not a measurement of individual red, green, or blue subpixels.
The active width is horizontal pixels ÷ PPI, and the active height is vertical pixels ÷ PPI. Those dimensions describe the image-bearing rectangle, not the monitor housing, stand, or mounting clearance. For installation measurements, use the manufacturer’s dimensional drawing.
Common monitor examples
These are calculations at the exact diagonal stated, not specifications for a particular model. Doubling both pixel counts at the same size doubles PPI and halves pixel pitch.
| Diagonal and resolution | PPI | Pitch (mm) |
|---|---|---|
| 24 in · 1,920 × 1,080 | 91.79 | 0.2767 |
| 27 in · 2,560 × 1,440 | 108.79 | 0.2335 |
| 27 in · 3,840 × 2,160 | 163.18 | 0.1557 |
| 32 in · 3,840 × 2,160 | 137.68 | 0.1845 |
Why a manufacturer’s PPI may differ slightly
A rounded marketing size is not always the exact active diagonal. The Dell U2724D specifications, for example, list 2,560 × 1,440 pixels, a 596.74 × 335.66 mm active area, and 108.97 PPI. Using a nominal 27-inch diagonal yields a slightly different estimate. Prefer the exact active dimensions when matching a specific product.
Screen pixels and CSS pixels are different inputs
The W3C CSS unit definition fixes 96 CSS pixels per CSS inch. That relationship does not say that every display has 96 physical pixels per inch. Display scaling and browser zoom affect the relationship between layout coordinates and device pixels. Use the screen’s native hardware resolution in this tool; a browser-reported window size cannot establish its physical diagonal.
Does higher PPI guarantee a better screen?
Higher PPI means the pixels are packed more closely. The calculation alone does not evaluate contrast, color accuracy, motion, text rendering, viewing distance, or your preferred text size. There is no pass/fail density score here. Compare the physical density for your task, then review the other display properties that matter to you.
This geometric model assumes square pixels and a rectangular active area. A rounded phone screen, a curved panel measured along an arc, or a display with non-square pixels may need manufacturer dimensions or a more specific model.
Printing an image instead?
A screen’s density does not set an image’s print resolution. If you have an image file and a proposed print size, use the image DPI and PPI calculator. The main converter and print planner also help you compare cropping, borders, and paper sizes.
Inputs are processed on this page and are not saved. Formula and source review: September 15, 2026. Send corrections to contact@pixelstoinches.org.