Sorting out monitor resolution and size – how to choose the best screen for home and office use

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If you’re just diving into external monitors, the vast array of options and resolutions stretching out before you might be enough to make you give up and buy an iMac just to have your monitor choice made for you. AppleInsider talks about the three biggest and most important factors for a daily-use monitor for general use: screen size, resolution, and scaling.

Typically, the average consumer can’t choose a monitor on Amazon and know it’s going to be perfect for them. It is not possible. You can tell what the physical size will be – although we all tend to underestimate the size of something once it’s on our desk – and you’re very clear on the price.

Even when the listing says it’s for a 4K monitor and you know 4K is good, that’s little to no help. That’s because 4K, like most monitor standards, is completely useless on its own. You should know that 4K on a 21 inch monitor will look good and 4K on a 49 inch will look bad.

And if only it were that simple. It’s easy to understand that 4K at 49 inches will be blurrier than the sharpness of this 21-inch 4K monitor. But, the latter is likely to make everything so small that it is also unusable.

Most of the time it’s because you just can’t read the screen when it’s at maximum resolution, but often it’s also because your Mac can’t handle it either.

The physical size of the screen is therefore a fact. The resolution is completely separate. What your Mac can deal with is a third fact. Each of these elements is at least reasonably easy to discover or understand, but you have to juggle all three.

What you can do, however, is enter armed with information and know what to look for. Find monitors from any store or site and know what the issues are, know where you need to spend time comparing – and know what you really need to compare.

A note before going much further. This article does not dwell on color spaces and calibration options on any given monitor – this article is intended as an introduction for the beginning monitor buyer. Calibration and the like are topics for another day.

Jason and the Monitor

If you’re buying a particular iMac or MacBook, you don’t have any options on the physical screen size. When you need a separate monitor, start with a 27-inch model like the BenQ PD2710QC or the Asus Designo MX27UC. We’ve included screenshots of 23-inch and even 19-inch screens for comparison, but there’s not even a price advantage to buying a monitor this size anymore.

For comparison, the text on the far left is from a 28-inch 4K monitor. In the middle is a 23-inch display and to the right a 19-inch display, all at their highest resolution.

A 27-inch model might be slightly overkill if you’re only working on one Word document at a time. Still, the only times you’ll regret buying a larger monitor are when you have to pay for it and when it doesn’t fit on your desk.

Our illustration of different screens is really different resolution. We happen to have taken them on a full range of monitor sizes, but what a screenshot shows is the resolution, not its appearance stretched across inches of glass.

Even so, there’s a screen resolution that stands out by being virtually invisible. Stuck between the screens of a MacBook Air and a MacBook Pro, you can see a thin sliver of what is effectively a 4K display.

Where 4K screens were once something you dreamed of, they are now clearly lost in the pack and should therefore be considered a minimum. Rather than using the term 4K or its various synonyms like Ultra HD, let’s be more specific. Do not accept a monitor with a resolution lower than 1920×1080 pixels.

If this is your primary monitor, consider 27 inches and 1920×1080 the minimum requirements.


Search Amazon for 27-inch monitors that run at 1920 x 1080 and now you know they’ll all look the same to you. There will be differences in quality between different manufacturers and at different prices, but a Mac icon or menu on one will look the same size and clarity on all of them.

You guessed it, but it’s one thing to understand the numbers, it’s another when you see them in front of you.

Here’s an example of the difference resolution makes. This is a screenshot of a 5K iMac at its highest resolution of 6400×3600 pixels. At the bottom right is the screen of a 2012 iMac which is 2560×1440. They are both 27-inch screens.

Two images, both from 27-inch iMacs.  The main is a 5K iMac where the inset, at the same pixel scale, is a pre-Retina 2012 iMac

Two images, both from 27-inch iMacs. The main is a 5K iMac where the inset, at the same pixel scale, is a pre-Retina 2012 iMac

When comparing two monitors, note the screen size, but also calculate the dots per inch. You are rarely given this information and it is probably because it would make comparisons too easy. Yet somewhere in the details of each monitor’s listing on each store’s website, there will be the pixel dimensions.

They are always given in horizontal number of pixels first, then vertical. Unfortunately, screen sizes are made in a different way. They are measured diagonally instead. You can use that or you can look up the physical dimensions of the monitor and just accept that any width and height listed include bezels.

There’s no way to be exact here, so use either number and divide the number of inches you get by the horizontal number of pixels. Even though it won’t be the right number of stitches per inch, it will be comparable. You will be able to see that this monitor will be blurrier than that one because it has much less dots per inch.

You could do the same calculation with the vertical number of pixels but that won’t help anymore. Vertical pixels are a concern though, as any lack of screen height is one of the first things you’ll notice when using a new monitor.


When you’ve decided on a display size and picked the highest resolution monitor your budget can support, check that your Mac can drive it. It’s easier to check when your Mac is currently on sale, because Apple lists specifications for the monitor sizes each machine can handle.

Apple is good at detailing the specifics of what different Macs can drive

Apple is good at detailing the specifics of what different Macs can drive

It’s surely a waste to buy a monitor when your Mac can’t drive it at its highest resolution. Except your monitor may outlast your current Mac. Also, this highest resolution is likely to get icons, menus, etc., that are far too small and finely detailed to read easily.

In this case, a monitor that displays more than you can usefully use is definitely a waste – except there’s that scaling.

The idea is easy enough to grasp but harder to visualize and apparently also harder for tech companies to manage. Windows is much less capable of successfully changing the display size of icons and text than Macs, for example.

Basically, you pick up your beautifully high resolution monitor and tell it to pretend it’s a less gorgeous, lower resolution screen. The only thing that remains the same is the physical size of the monitor.

Apple strives to make this as easy to understand as possible, but only after you realize you need it. We’ve seen people squint at their MacBook screens, unaware that with a click or two they could save an optician’s bill.

Regardless of the size or resolution of your monitor, you can access System Preferences, Attach and chose Resolution: Scaling. Below a certain resolution, usually 4K, you’ll see a list of resolutions the monitor can handle – probably. In this case, you’d choose from the list and review how each looked – but that trial-and-error approach is hopefully behind all of us now, as we won’t be buying a monitor under 4K.

When it’s a 4K or higher monitor, Apple shows you a graphical representation of how upscaling works.

Depending on the monitor and Mac, this representation will show you four or five possible settings.

Above a certain high resolution, Apple shows a simplified system for choosing how much to dim your display

Above a certain high resolution, Apple shows a simplified system for choosing how much to dim your display

Apple doesn’t give any numbers or pixel counts, it just has a range from Larger text at More space.

The difference of a stop on Apple's larger text for more space makes

The difference of a stop on Apple’s larger text for more space makes

Don’t go looking for a tape measure on this one, but just to give you an idea of ​​the difference scaling makes, here’s an example. These are two side by side images of the LG 34 inch monitor and although they are cropped so you can see them they show different scaled resolutions.

Specifically, it is a one-step difference in the range from Larger text at More space and you can see it’s significant.

This far and no further

What you can’t see, and what no one can show you, is precisely what it all looks like on every monitor you consider. Armed with this knowledge and hopefully a decent return policy, you’ll be well on your way to getting the ideal combination of size, resolution, and scaling for your needs.

It might not be worth finding, but there is an Open in low resolution option for every app.

It might not be worth finding, but there is an Open in low resolution option for every app.

There’s just one more thing, though. This might be macOS’s most obscure feature or maybe we’ve never needed it before, but you can tell an individual app to display in a lower resolution. By himself.

Go to your Applications folder, right-click on any application and press Command-I Choose To file, Obtain informations.

You will find a marked checkbox Open in low resolution. As always, Apple doesn’t give any pixel dimensions, but otherwise it works. So if you need high resolution for your Final Cut Pro X work but it makes Microsoft Word too thin and small to use, you can make Word open in low resolution.

It does make a difference, but you need to be on a very high resolution monitor to see any significant change.

Edward N. Arrington