To set up dual monitors, connect the second screen, open your display settings, choose Extend so your desktop spans both screens, then drag the screens into the layout they have on your desk. On Windows, press the Windows key and P to switch between modes; on a Mac, check how many external displays your chip supports first, because Apple says a MacBook Pro with an M5 chip supports two and closing the lid won't add more. Then put your main screen directly in front of you, at least 20 inches away.
A second screen is one of the simplest upgrades to a home office, and it's also one of the easiest to set up badly. I read Microsoft's multiple monitors guide, Apple's external display limits for MacBook Pro and OSHA's workstation guidance on monitors. Here's the setup, start to finish.
Set up two monitors on Windows
- Check your cables are connected to your PC or dock, and run Windows Update.
- Open Settings, then System, then Display. If the second screen isn't shown, open Multiple displays and select Detect.
- Select Identify to see which number belongs to which screen.
- Drag the numbered screens so they match their positions on your desk, then select Apply.
- Press the Windows key and P and choose Extend to spread your desktop across both.
Microsoft lists four modes in that Windows key and P menu: PC screen only, Duplicate for the same picture on both, Extend for one desktop across both, and Second screen only. For working, Extend is the one you want. Under Multiple displays there are two settings worth switching on if you use a laptop on a dock: remember window locations based on monitor connection, and minimise windows when a monitor is disconnected.
Check your Mac's display limit first
On a Mac, the chip decides how many external screens you can run, and Apple's support page is specific. Here's what it says for recent MacBook Pro models.
| MacBook Pro chip | External displays supported |
|---|---|
| M5 | Up to two, alongside the built-in display |
| M5 Pro | Up to three |
| M5 Max | Up to four |
| M4 or M4 Pro | Up to two |
| M4 Max | Up to four |
Two notes from the same page save a lot of frustration. Closing the lid of your MacBook Pro won't increase the number of external displays it supports, and a hub or daisy-chained displays can put several screens on one Thunderbolt port but won't raise the maximum. Apple also says to connect the display with the highest resolution first.
Where to put each screen
OSHA's guidance is written for one monitor, but it's the right starting point for two. It says to put the monitor directly in front of you and at least 20 inches away, with a preferred viewing distance of 20 to 40 inches. The top line of the screen should be at or below eye level, with the centre of the screen about 15 to 20 degrees below horizontal eye level. It also says to place monitors perpendicular to windows, and warns that tilting a screen back can pick up glare from ceiling lights.
- Put the screen you use most directly in front of you, following OSHA's advice.
- Place the second screen beside it, angled towards you, at the same height.
- If you use both equally, centre the pair so the join sits in front of your nose.
- Match the arrangement in your display settings so your mouse moves across naturally.
If you're rebuilding your desk at the same time, read my guide to the benefits of a standing desk and my pick of ergonomic office chairs.
My advice on a two-screen desk
Decide which screen is your main one and put it straight in front of you; the second screen is for reference, not for craning your neck all day. On a Mac, check your chip's limit before you buy a second monitor, because no adapter will get you past it. And spend two minutes matching the layout in your settings, because a mouse that jumps off the wrong edge will annoy you every single day.
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Frequently asked questions
How do I set up dual monitors on Windows?
Connect the second screen, open Settings, System, Display, use Detect if it isn't shown, drag the screens to match your desk and select Apply. Then press the Windows key and P and choose Extend.
How many monitors can my MacBook Pro run?
Apple says a MacBook Pro with the M5 chip supports up to two external displays, M5 Pro up to three and M5 Max up to four. Closing the lid doesn't increase the number.
Why isn't my second monitor detected?
Microsoft suggests checking the cables, running Windows Update, then using Settings, System, Display, Multiple displays, Detect.
How far away should my monitor be?
OSHA says at least 20 inches, with a preferred viewing distance of 20 to 40 inches from your eyes to the screen.
Should two monitors be the same height?
Keeping both at the same height, with the top of each screen at or below eye level as OSHA advises, avoids constant neck movement between them.
