PPI / Pixel Density Calculator
Calculate a screen's pixel density (PPI) from its resolution and diagonal size, with the dot pitch, physical dimensions, and total megapixels.
كيفية استخدام هذه الحاسبة
- 1Enter the screen's horizontal and vertical resolution in pixels.
- 2Enter the diagonal screen size in inches.
- 3Read the pixel density (PPI) and how sharp it is.
- 4See the dot pitch, physical dimensions, and total megapixels too.
طريقة الحساب
Pixel density
diagonal pixels = √(width² + height²) PPI = diagonal pixels ÷ diagonal inches dot pitch (mm) = 25.4 ÷ PPI physical width = horizontal pixels ÷ PPI
Pixel density, measured in pixels per inch, describes how finely a display packs its pixels, which is what actually governs how sharp it looks. It is calculated by finding the length of the screen's diagonal in pixels — using the Pythagorean theorem on the horizontal and vertical resolutions — and dividing by the diagonal measured in inches. The result tells you how many pixels fit into each inch of screen. From it, the dot pitch (the physical distance between pixel centres, the reciprocal of density in millimetres) and the screen's physical dimensions follow directly. Crucially, pixel density depends on both resolution and size: the same resolution spread over a larger screen has a lower density and looks coarser, which is why resolution alone is a poor guide to sharpness. A high-resolution phone can be far sharper than a much higher-resolution television.
مثال محلول
A 24-inch monitor at 1920×1080 has a diagonal of √(1920² + 1080²) ≈ 2203 pixels, so its density is 2203 ÷ 24 ≈ 92 PPI — fairly coarse. The same 1920×1080 on a 5-inch phone would be about 440 PPI, sharp enough that individual pixels are invisible at arm's length.
PPI / Pixel Density Calculator: الدليل الكامل
Why resolution alone doesn't mean sharp
Marketing loves resolution numbers — 1080p, 4K, and so on — but resolution by itself says nothing about how sharp a screen looks. Sharpness is about pixel density: how many pixels are packed into each inch. The same resolution can look razor-sharp or noticeably blocky depending entirely on the size of the screen it is spread across. A 1920×1080 image is crisp on a 5-inch phone and coarse on a 55-inch television, because on the big screen those same pixels are stretched over eleven times the diagonal, making each one large enough to see.
This is why pixel density, not resolution, is the honest measure of a display's fineness. A cheaper phone with a 'lower' resolution can easily out-sharpen a giant monitor with a 'higher' one, because its pixels are far more tightly packed. When comparing screens, the PPI figure — which combines resolution and size into a single number — tells you what your eyes will actually perceive. The calculator exists to surface this hidden number, since manufacturers usually advertise resolution and size separately and leave you to work out the density that matters.
Retina displays and the limits of the eye
The term 'Retina display', coined by Apple, marked a shift in how screens were sold — from raw pixel counts to whether the eye can see the pixels at all. The idea is that beyond a certain pixel density, at a normal viewing distance, the individual pixels become too small for the human eye to resolve, so the image looks perfectly smooth. Past that point, adding more pixels yields no visible benefit. For a phone held about a foot away, that threshold is roughly 300 PPI; the exact figure depends on the viewing distance and eyesight.
The crucial insight is that the threshold depends on distance. A phone is held close, so it needs a high density to look flawless. A laptop sits farther away and can look just as sharp at a lower density. A television, viewed from across the room, needs far fewer pixels per inch to appear pixel-free, which is why a 4K TV and a 4K phone have wildly different PPI yet can both look 'retina-sharp' at their intended distances. This is also why chasing ever-higher resolution on large, distant screens delivers diminishing returns — beyond what the eye can resolve, the extra pixels are wasted. Understanding density and viewing distance together explains why the 'best' screen is not simply the one with the most pixels.
Where pixel density matters in practice
Pixel density affects real decisions across many devices. When choosing a monitor, a low PPI can make text look fuzzy and tiring to read for long periods, while a very high PPI may require the operating system to scale the interface so elements are not too tiny. For phones and tablets, density is a headline feature precisely because they are held close, where the eye is most demanding. Even for the same device, density interacts with scaling settings that trade physical sharpness against usable screen space.
The concept extends beyond screens too. Print resolution is measured in the closely related DPI (dots per inch), where 300 DPI is a common standard for sharp printing because, as with screens, it is around the limit of what the eye resolves at reading distance. Photographers and designers think in these terms when deciding how large an image can be printed before it looks pixelated. Whether you are buying a monitor, comparing phones, setting up a display, or preparing an image for print, the underlying question is the same: are the pixels small enough, at the distance they will be viewed, to disappear? The pixel density this calculator provides is the number that answers it.
الأسئلة الشائعة
How do I calculate pixel density (PPI)?
Find the diagonal in pixels with √(width² + height²), then divide by the diagonal in inches. A 24-inch 1920×1080 monitor has a diagonal of about 2203 pixels, so its density is 2203 ÷ 24 ≈ 92 PPI. It combines resolution and size into one sharpness figure.
Does higher resolution always mean a sharper screen?
No — sharpness depends on pixel density, not resolution alone. The same resolution looks sharp on a small screen and coarse on a large one, because the pixels are spread over more area. A phone can out-sharpen a much higher-resolution TV. PPI is the number that reflects what you'll actually see.
What PPI counts as a 'Retina' display?
Roughly the density at which the eye can't see individual pixels at normal viewing distance — about 300 PPI for a phone held close. But it depends on distance: a laptop or TV viewed farther away looks equally sharp at a lower PPI, which is why devices have very different 'retina' thresholds.
What is dot pitch?
Dot pitch is the physical distance between neighbouring pixels, the reciprocal of pixel density — 25.4 ÷ PPI in millimetres. A smaller dot pitch means pixels are closer together and the image is finer. A 92 PPI screen has a dot pitch of about 0.28 mm.