What a percentage does to your desktop
At 100% one interface pixel is one screen pixel, and Windows treats that as 96 DPI. At 200% each interface pixel takes a 2 × 2 block of real ones, so text and icons double in size and the desktop gets smaller. Here's a 4K screen at four settings:
- 100%: 3840 × 2160
- 125%: 3072 × 1728
- 150%: 2560 × 1440
- 200%: 1920 × 1080
The taskbar takes a strip of that. At 200% a 4K screen leaves 1920 × 1032 for windows.
Which percentage the calculator suggests
The Display Scaling Calculator matches a screen's pixel density to a reference: a 27-inch 1080p monitor at 100%, which has 81.59 PPI. A screen twice as dense as that gets 200%, so text lands at the same physical size. It's a target for comfortable reading, not what Windows picks by default.
- 24-inch 1080p: 113% exactly, so 100%
- 27-inch 1440p: 133% exactly, so 125%
- 27-inch 4K: 200% exactly, so 200%
- 32-inch 4K: 169% exactly, so 175%
Many people pick a lower number for more room. A 27-inch 4K at 150% gives a desktop of 2560 × 1440, with smaller text than the target.
Laptops get a trimmed number because you sit closer to them, so the calculator scales its target by 0.84. A 14-inch 2880 × 1800 laptop lands at 250%.
Why some apps look blurry
An app has to tell Windows that it knows how to scale. Apps that don't are treated as running at 96 DPI, which is 100%. On a scaled display Windows stretches their image to the right size, and the stretch makes them blurry. Apps that handle each monitor's scale themselves stay crisp.
Two monitors with different scale factors make this more likely. An app that only knows one scale can look soft on the other screen. Matching the scale on both screens, or updating the app, usually helps.