Mac monitor ppi and scaling calculator
Will this monitor look sharp on a Mac? Size and resolution are enough to tell you. The calculator works out pixel density and which of macOS's scaling modes the panel will end up in.
At 1× the interface is too small; at a clean 2× it is too large. To get a comfortable size macOS renders a bigger frame and squeezes it onto the panel by a non-integer factor. It works, and many people never mind it, but fine text loses some crispness and the GPU does extra work.
- Looks like (recommended)
- 2560 × 1440
- macOS renders at
- 5120 × 2880
- Resampling to panel
- × 0.75 (non-integer)
- Physical size
- 23.5 × 13.2 in
- Pixels stop being visible beyond
- 21 in / 54 cm
Common monitors at a glance
| Monitor | ppi | On a Mac | Looks like |
|---|---|---|---|
| 24″ 1080p | 92 | Native 1× | 1,920 × 1,080 |
| 27″ 1440p | 109 | Native 1× | 2,560 × 1,440 |
| 24″ 4K | 184 | Clean 2× | 1,920 × 1,080 |
| 27″ 4K | 163 | Fractional scaling | 2,560 × 1,440 |
| 32″ 4K | 138 | Fractional scaling | 3,072 × 1,728 |
| 27″ 5K | 218 | Clean 2× | 2,560 × 1,440 |
| 32″ 6K | 216 | Clean 2× | 3,008 × 1,692 |
| 34″ ultrawide 3440 × 1440 | 110 | Native 1× | 3,440 × 1,440 |
| 34″ 5K2K ultrawide | 163 | Fractional scaling | 3,456 × 1,458 |
| 49″ 5120 × 1440 | 109 | Native 1× | 5,120 × 1,440 |
For reference, Apple's own displays — Studio Display, 24-inch iMac, Pro Display XDR — all sit at 218 ppi, and the 13-inch MacBook Air M4 at 224 ppi.
How the numbers are worked out
Pixel density is the diagonal in pixels, √(width² + height²), divided by the diagonal in inches. That part is exact.
The verdict rests on how macOS draws its interface. It is designed for roughly 110 logical pixels per inch at desk distance, and Retina screens draw each logical pixel as a 2 × 2 block — which is why Apple's desktop displays are all about 218 ppi. The calculator checks two clean options first:
- 2× works when half the panel's ppi lands between about 90 and 125 — the interface is a sensible size and nothing is resampled.
- 1× works when the panel's own ppi lands in that range — sensible size, no scaling, but standard-density text.
If neither fits, a comfortable size needs a non-integer mode. macOS renders the desktop at twice the "looks like" resolution and then scales that frame down to the panel. The resampling factor above is that squeeze; anything other than 1 means fine detail is being interpolated.
The 90–125 band is a rule of thumb from how macOS behaves, not a figure Apple publishes, and comfort depends on your eyes and how far you sit. The "looks like" suggestion is rounded to a width close to the options macOS's Display settings usually offer; your exact list depends on the monitor and the Mac. The viewing-distance figure assumes one arcminute of visual acuity (20/20 vision).
What to do with the result
If the verdict is fractional, the monitor still works — it just is not the sharpest way to spend the money on a Mac. The reasoning, the trade-offs between 24-inch 4K, 27-inch 5K and 32-inch 6K, and specific models are in External monitor for a MacBook Air: ppi, not size. If you are planning more than one screen, check how many external displays a MacBook Air M4 drives first.