- How do you calculate PPI?
- Take the diagonal resolution in pixels and divide it by the diagonal in inches. The diagonal resolution is the hypotenuse of the pixel grid: the square root of (width² + height²). For a 2560 × 1440 screen that's √(2560² + 1440²) = 2937.21 pixels across the diagonal. Divide by a 27-inch diagonal and you get 108.79 PPI. The reason you use the diagonal rather than the width is that the diagonal is the one physical measurement manufacturers publish — nobody prints the bezel-to-bezel width on the box.
- What's a good PPI for a monitor?
- For a desktop monitor viewed at arm's length, roughly 24 inches away, anything at or above 140 PPI looks clean and above about 160 PPI is effectively pixel-free. 27-inch 4K lands at 163 PPI. 27-inch 1440p lands at 109, which most people find acceptable but not crisp — text edges are visible if you look. 24-inch 1080p is 92 PPI and you will see the pixels in text. The catch is that PPI alone isn't the answer: a TV at 110 PPI looks flawless because you sit six feet away. Distance is half the equation, which is why this tool prints the distance it assumed instead of handing you a bare number.
- Is PPI the same as DPI?
- They're used interchangeably in conversation and they mean different things. PPI (pixels per inch) describes a display: how many light-emitting pixels sit in an inch of screen. DPI (dots per inch) describes a printer: how many ink dots it lays down per inch of paper. Printers commonly run 300 to 1200 DPI because ink dots are binary — a dot is there or it isn't — so it takes several dots to simulate one shade. A screen pixel can be any colour on its own, so a 300 PPI phone looks as smooth as a 1200 DPI print. If you're sizing an image for printing rather than measuring a screen, the pixels to inches converter is the tool that does that job.
- What is dot pitch, and how does it relate to PPI?
- Dot pitch is the same fact upside down: the distance from the centre of one pixel to the centre of the next, in millimetres. Convert with 25.4 ÷ PPI, since there are 25.4 mm in an inch. A 108.79 PPI monitor has a 0.2335 mm dot pitch. Lower is sharper, which is the opposite direction from PPI and the reason the two numbers get confused. Dot pitch is the older convention, from the CRT era, and it still shows up on industrial and medical display spec sheets where physical pixel size matters more than a density figure.
- Why does my aspect ratio show '≈ 16:9' instead of an exact number?
- Because the exact reduction is often useless. 1366 × 768 — the resolution of a whole generation of budget laptops — reduces to 683:384, which is arithmetically correct and means nothing to anyone. The panel is sold, described and designed as 16:9, and it's within 0.05% of it. So the exact ratio is shown when it's a ratio people recognise, and the nearest conventional one with a '≈' when it isn't. Phone screens are the other common case: 2532 × 1170 reduces to 422:195, which is 19.5:9 to everyone who has ever read a phone spec sheet.
- How does viewing distance change the answer?
- It changes it completely. The eye resolves detail at roughly one arcminute, so what matters isn't pixels per inch of glass but pixels per degree of your field of view — PPD. Double the distance and you halve the angular size of each pixel, which doubles the effective sharpness. That's why a 65-inch 8K TV at 136 PPI, seen from six feet, is far past what your eye can resolve, while a 92 PPI monitor a foot and a half from your face is not. The verdict line here assumes 12 inches for phone-sized screens, 24 for monitors and laptops, and 72 for TVs, and it prints the assumption so you can adjust it in your head if you sit closer.
- Does higher PPI always mean a better screen?
- No, and past a point it costs you. Once a display exceeds what you can resolve at your normal distance, extra pixels buy nothing visible while consuming GPU time, battery and bandwidth — a 4K panel pushes four times the pixels of a 1080p one at the same frame rate. High density also creates a scaling problem: at 163 PPI, unscaled interface text is roughly half the physical size it is at 92 PPI, so the operating system has to scale, and applications that scale badly end up blurry on the sharper screen. Colour accuracy, contrast ratio, refresh rate and panel type all matter at least as much once you're past about 140 PPI.
- Can I use this for a phone, a tablet, or a TV?
- Yes — the arithmetic is identical for any rectangular screen, and the tool adjusts only the viewing distance it assumes. Phones land between 380 and 500 PPI, tablets between 220 and 270, laptops between 95 and 230, desktop monitors between 90 and 220, and TVs between 30 and 140. The ranges overlap because the distances differ: a 40 PPI 85-inch TV and a 460 PPI phone can look equally sharp from where you actually sit.
- What counts as a 'Retina' display?
- It's a marketing term with a technical idea behind it: a display whose pixels are too small to distinguish at its intended viewing distance. The threshold works out to about 60 pixels per degree of vision, which translates to roughly 300 PPI at phone distance, 220 at laptop distance, and 160 at desk-monitor distance. The 'Sharp' verdict here uses that same 60 PPD threshold, so it agrees with the claim wherever the claim is honest — and disagrees where a screen is described that way and sits closer to your face than the number assumes.
- Is anything I type here sent anywhere?
- No. The calculation runs in your browser and nothing is sent to a server or stored. Close the tab and it's gone. Most calculators like this one sit three clicks inside a review site that wraps one number in three thousand words and an affiliate rail — this is just the calculator.
