PPI Calculator: How Sharp That Monitor Actually Looks

The two questions people ask about a monitor before they buy it are whether it will look sharp and whether everything on it will be too small. Both are geometry, and both have an answer you can check, which is what this PPI calculator is for.

This works out the pixel density, the distance at which the pixels stop being resolvable, how much of your field of view the picture fills, and which Windows scale puts the interface back to the size it was drawn at. Every step is shown, and every constant it uses names the standard it came from.

In this guide

1. The PPI calculator
2. Where every number here comes from
3. What this cannot tell you
4. Monitors on this site in the range the PPI calculator gave you
5. Sources
6. Related guides

The PPI calculator

Where every number here comes from

No part of this was measured on a bench here. This site works from published specifications and from what owners report, and every number below is either one you typed in or a published figure with its source named next to it.

The figures this page supplies

• Windows reference density: 96 DPI. Windows defines 100% scaling as 96 dots per inch: a point of interface at 100% is 1/96 inch. Every scale percentage is measured against that number.
• Inches per unit at one arcminute: 3,437.7500. One arcminute is the angle a person with 20/20 vision can just resolve, which is the definition behind the Snellen 20/20 line. 1 / tan(1 arcminute) is 3437.75, so a detail becomes indistinguishable at 3437.75 times its own size.

Why each step is the step it is

• Diagonal in pixels: Math.sqrt(res_w * res_w + res_h * res_h). Pythagoras on the pixel grid. Nothing is assumed about the panel.
• Pixel density: diag_px / diag_in. The pixel diagonal divided by the inch diagonal. This is the definition of pixels per inch, not an estimate of it.
• Picture width: diag_in * res_w / diag_px. The panel and its pixel grid are the same shape, so the width is the diagonal scaled by the width's share of the pixel diagonal.
• Picture height: diag_in * res_h / diag_px. The same proportion, taken down the screen instead of across it.
• One pixel measures: 25.4 / ppi. 25.4 mm to the inch, divided by the pixels in an inch.
• Pixels stop being visible at: arcmin_in / ppi. A pixel subtends one arcminute at 3437.75 times its own width, and one arcminute is what 20/20 vision resolves. Closer than this and you can see the grid; further and you cannot. It is not a recommendation about where to sit.
• One pixel at your distance: arcmin_in / (ppi * distance_in). The same relation read the other way round. At 1.00 you are exactly at the limit; below 1.00 the pixels are already too small for the eye to separate.
• The picture fills this much of your view: 2 * Math.atan(width_in / 2 / distance_in) * 180 / Math.PI. Plain trigonometry on the picture width and your distance. SMPTE's recommendation for video is at least 30 degrees and THX recommends about 36, so those are the numbers to read it against.
• Scale that restores intended size: ppi / ref_dpi * 100. Interface drawn for 96 DPI appears smaller in proportion as density rises, so multiplying by the density's ratio to 96 puts it back to the size it was drawn at.
• Nearest scale Windows offers: nearest(scale_raw, [100, 125, 150, 175, 200, 225, 250, 300, 350, 400]). Windows offers a fixed ladder of scales, so the raw figure is snapped to the closest rung on it. Windows also weighs viewing distance in its own recommendation; this is the size-matching half of that, not Windows' algorithm.
• Desktop width at your chosen scale: Math.round(res_w / (scale_pct / 100)). At 150% each interface point is 1.5 pixels across, so the desktop behaves as though it were this many pixels wide. This is the number that decides how much fits side by side.
• Desktop height at your chosen scale: Math.round(res_h / (scale_pct / 100)). The same division taken down the screen.

What this cannot tell you

Every calculator has an edge, and a page that hides its edge is worse than no page at all. Here is this one's.

• It is geometry, not a verdict. Two panels with identical numbers here can look very different: coating, contrast, subpixel layout, brightness and colour are not in this arithmetic, and this site has not had either panel in its hands.
• The distance where pixels disappear assumes 20/20 vision. Better than that and you will want to sit further back; worse, or wearing the wrong prescription, and you can sit closer than it says.
• Windows' own recommended scale also weighs how far away you sit and what kind of display it thinks it is. This works out the size-matching half only, which is why it sometimes differs by one rung.
• Text rendering differs between Windows and macOS, and a scale that looks right on one can look soft on the other at the same density.

Monitors on this site in the range the PPI calculator gave you

These follow from the answer above and nothing else. Each heading below covers one span of results, so read the one the calculator pointed you at and ignore the rest.

Under 100 PPI

A 24-inch 1080p panel or a 32-inch 1440p one. Text is visibly made of pixels at desk distance, and nothing needs scaling: everything is already big.

Best 1440p Gaming Monitor Under $300 (4 Honest Picks) covers this range in full.

100 to 120 PPI

The 27-inch 1440p range, which is where most desks end up. Sharp enough at normal distance, and usable at 100% scale.

Best 1440p Gaming Monitor Under $300 (4 Honest Picks) covers this range in full.

144Hz Gaming Monitor, 5 Best Picks Compared for 2026 covers this range in full.

120 to 145 PPI

A 32-inch 4K panel. Noticeably sharper, and the point at which a scale above 100% starts being the comfortable choice rather than an accessibility setting.

4K Monitor vs 1440p in 2026, 5 Picks and the Honest Call covers this range in full.

Above 145 PPI

A 27-inch 4K panel or a high-density laptop screen. Very sharp, and effectively unusable at 100% scale: plan on 150% or more, and check that the applications you live in handle it.

4K Monitor vs 1440p in 2026, 5 Picks and the Honest Call covers this range in full.

Monitor Buying Guide 2026: The Specs Worth Paying For covers this range in full.

The scale figure is the size-matching half of what Windows does, not the whole of Windows' own recommendation, so treat a one-rung disagreement with your own machine as normal rather than as either of you being wrong. No PPI calculator can see which display your machine thinks it is driving.

Sources

• Microsoft: high DPI desktop application development on Windows: States the 96 DPI baseline that every Windows scale percentage is measured against.
• Microsoft: make Windows easier to see (display scaling): The scales Windows actually offers, which is the ladder the suggestion snaps to.
• SMPTE ST 2080-3 and THX certified viewing distance: Published minimum horizontal viewing angles for video, which is what the field-of-view figure is read against.
• Snellen visual acuity and the one-arcminute limit: 20/20 vision is defined as resolving detail subtending one arcminute, which is where the 3437.75 comes from.

Monitor Buying Guide 2026: The Specs Worth Paying For

Every pick on this page, and the ones from the other guides, sit together in my Amazon storefront.

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