DisplayMath

What it is

DisplayMath is a free web-based calculator that helps users visualize and compare screen sizes. It calculates physical dimensions, pixel density (PPI), aspect ratios, field of view, and other viewing metrics based on resolution and diagonal size. Users can compare multiple displays side-by-side on a single to-scale canvas, adjust viewing distance to see how much of their vision the screen fills, and on supported iPhones or iPads, use augmented reality to see screens at true size on their wall. The tool also provides calculators for TV sizing, monitor mounting height, and pixels-per-degree measurements, with an optional €9 Planning Pack for creating mounting plan PDFs.

Questions from the bench

What is PPI (pixels per inch)?

PPI tells you how many pixels fit in one inch of screen. Higher PPI means sharper text and finer detail at the same viewing distance. A 27-inch QHD monitor has around 109 PPI, while the same size in 4K reaches about 163 PPI. A 55-inch 4K TV sits near 80 PPI, which is fine because you watch it from much farther away.

What is pixel pitch?

Pixel pitch is the center-to-center spacing of neighbouring pixels, the inverse of PPI. A 27-inch QHD panel has a pitch of about 0.233 mm, while LED walls are specified this way directly with pitches measured in whole millimetres.

How far should you sit?

The cinematic seat row gives the distance for a 40 degree horizontal field of view as a starting point for an immersive picture. The TV size calculator starts with your room and lets you adjust the viewing angle.

What does 1800R mean on a curved monitor?

The R number on a curved monitor is the radius of its curve in millimetres, so an 1800R panel follows a circle with a 1.8 m radius. Smaller numbers mean a tighter curve. At a viewing distance equal to the radius, points along the horizontal centre line are equally far from your eyes.

Will it look sharp from my seat?

Pixel density and viewing distance both affect visible detail. The pixels per degree calculator combines them into central pixels per degree, with a clearly labelled 60 PPD reference. It is a comparison aid, not a guarantee that pixels or resolution differences become invisible.