Choosing an external display for a Mac, and the scaling trap
· 5 min read
Monitors are usually sold on size, panel type and refresh rate. For a Mac, the number that decides whether you are happy is pixel density, and it is rarely on the box.
Work out the density
Pixels per inch follows from resolution and diagonal size. The common combinations:
- 27-inch 1440p: about 109 ppi
- 27-inch 4K: about 163 ppi
- 27-inch 5K: about 218 ppi
- 32-inch 4K: about 138 ppi
- 24-inch 4K: about 184 ppi
A MacBook’s own display is around 254 ppi, which is what your eyes are calibrated to.
macOS renders its interface at 2x and scales down, which looks excellent at high density and merely acceptable at low. It does not do the fractional scaling and font hinting that makes Windows look sharper on the same panel. That difference is why a monitor praised by PC users can disappoint on a Mac.
The comfortable choices
27-inch 5K. Matches Retina density. Everything is crisp, macOS runs at a clean 2x, and no scaling compromises are involved. The expensive option and the one with no caveats.
24-inch 4K. Also high density, cheaper, smaller. Excellent if the size suits you.
32-inch 4K. A reasonable middle. Density is lower than Retina, and the extra size means you sit further back, which compensates. Popular for good reason.
27-inch 4K. Workable. Runs sharp at “looks like 1920 x 1080”, which many find too large, and less sharp at intermediate scaled settings.
27-inch 1440p. The one to think twice about. Text will be softer than you are used to. Fine for many people, and it is the most common source of the complaint. Why text looks blurry on an external monitor covers what can be done about it.
The scaling trap
macOS offers “looks like” resolutions rather than raw ones. Choosing one that is not a clean fraction of the panel’s native resolution means the Mac renders at a higher internal resolution and scales down, which costs a little sharpness and some graphics work.
The clean options are native, and half of native. Anything between involves compromise.
On a 4K panel: “looks like 1920 x 1080” is clean and large. “Looks like 2560 x 1440” is scaled and gives more usable space at slightly reduced sharpness. Most people choose the second and are happy.
Test this before committing, if you can. It is very hard to predict which side you will land on.
Refresh rate
For general work, 60 Hz is entirely adequate and what most Macs will drive alongside high resolution.
Higher rates are pleasant for scrolling and matter for games. On a Mac they also consume bandwidth that might otherwise go to resolution or a second display. If you have to choose, resolution serves most work better.
Connection
USB-C or Thunderbolt input means one cable for video, power and often a USB hub in the monitor. That is the arrangement worth having on a laptop.
Check the monitor’s power delivery figure if you intend it to charge the Mac. Many supply 65 W or less, which is fine for a 13 or 14-inch machine and slow for a 16-inch.
Confirm the port carries video at all; some monitor USB-C ports are data and power only. Why a USB-C cable can charge but not carry video covers the cable side.
Before buying
- Check how many displays your Mac supports at the resolution you want. How many external displays your Mac can drive.
- Work out the ppi of the monitor you are considering.
- Decide whether you can live with scaled rather than native.
- Confirm the connection carries video and enough power.
Questions
Is an ultrawide good for a Mac? Depends on density. Many have modest ppi and will look soft. A 5K ultrawide is a different proposition from a 1440p one.
Should I match the monitor to my MacBook’s display? You cannot exactly, and 5K at 27 inches is the closest common option. Below that, expect a visible difference when you look between them.
Do I need an Apple display? No. Any monitor works. Apple’s are high density with good build, at a price that reflects it. Third-party 5K options exist and are worth comparing.
Will a curved monitor cause problems? No technical issue on a Mac. It is a preference, and less popular for text work than for games.