This is a question which I see asked a lot either online or by customers of ours looking to put together a new computer system for trading.
As with most things in life, the answer is usually, ‘it depends’…
Not massively helpful I know, but it is the truth, here’s why.
The Two Most Important Factors When Picking the Right Size Monitor
Choosing the right sized monitor for your trading requirements comes down to two factors, the physical size and then the resolution of the screen.
Most people can easily comprehend the impact of a specific size of screen is going to have on them physically.
What I mean by this is that it’s fairly easy to imagine what having a 24” screen or a 32” on your desk is going to look like, and if you can’t picture it then a few minutes with a tape measure will help.
The thing which many people are unable to envisage is what a difference one resolution is going to make over another one.
To be honest, there are a lot of people I speak to who don’t even know what a screen resolution is, and why should they, I’m sure there’s a ton of stuff that they know which I have no knowledge of.
The resolution is just as important, if not more so, as the size of a screen, and both need to be taken into account together when selecting your next screen.
What is a Screen Resolution
When we are talking about screen resolution for monitors we are basically describing the number of pixels that the screen is able to show.
A pixel is essentially a tiny dot of light, screens use pixels to produce the image you see on your screen, so a screen resolution of 1920 x 1080 means that the screen can display 1,920 pixels horizontally and 1,080 pixels vertically, this gives you a total pixel count of 2,073,600 pixels.
We go into a lot more details on screen resolutions over on the Multiple Monitors Blog – Screen Resolutions Guide (https://www.multiplemonitors.co.uk/blog/monitor-screen-resolutions/) if you want a more deep dive into the subject.
For the purposes of this discussion, the important thing you need to know is that a screen resolution is simply a description of how many pixels the monitor can display.
The Real-World Impact of Higher Resolution Screens
Generally speaking the higher resolution a screen is then the more pixels it has available to display your information.
This can work in one of two ways.
1. Higher Definition / More Detail – If you have two screens of the same size and one has more pixels than the other (I.e. it is higher resolution) then the pixels on the higher resolution screen need to be smaller to fit them into the same physical size, this means that the images displayed on the higher res screen will look smoother or more detailed.
Why is this? Imagine trying to create a circle out of square lego blocks, you could do it but it would be impossible to create a smooth edge due to the blocky nature of the bricks you were using.
If I then gave you another set of blocks which were a lot smaller then the same size circle would look a lot smoother.
If you could then use blocks which were tiny then at some point you would not be able to tell that the ‘circle’ was made up of blocks at all, it would look like a smooth curved line.
The size of each circle would be the same but the larger number of smaller sized blocks (greater number of smaller pixels) works to make sure the last circle looked a lot smoother / more detailed.
2. More Space to Work With – If we go back to comparing two screens, one with a higher resolution than the other, then what we are saying is that the higher resolution screen has more pixels.
This means that if you are running a charting package with your trading software, and the chart takes up a space of 400 pixels wide by 300 pixels tall, then if your higher resolution screen has more pixels available then you would have more ‘room’ to fit in more charts.
As a trader the second benefit of a higher resolution screen is what you want, more space to lay out your charts, spreadsheets and Netflix (maybe?), this is far more beneficial to you than making your charts look a bit nicer.
Can you have both benefits? I.e. greater detail / definition and more space to work with? You can to a certain extent but you have to be careful and there are drawbacks.
Combining Screen Size & Resolution
As we have discussed, with two monitors the same size, the higher resolution one has a greater number of pixels, so these pixels on the higher resolution screen need to be reduced in size to be squeezed into the same physical space.
This reduction in pixel size has a major impact on your experience of using the screen.
Take a 4K screen for example. 4K is the shorthand name given to a resolution of 3840 x 2160 pixels, exactly four times the resolution of a standard 1920 x 1080 screen (technically these are referred to as Full HD or FHD screens).
If you have a 21.5” or 24” screen on a standard computer then it is more than likely that it is a FHD (1920 x 1080) resolution screen. These are very common and in widespread use and have been for many years now.
With an FHD screen at these sizes text and icons, unless you have fairly major vision issues, will appear perfectly readable / usable.
If we have a 4K screen of the same size, which has four times the number of pixels, then all your text, icons, charts, practically anything that you display on the screen will appear four times smaller.
This is because your software does not know what size screen you have connected, all it knows is that fonts, lines, buttons and images should take up a certain number of pixels. When your pixels are four times smaller then everything is basically unusable.
Hopefully you can see that simply going for a higher resolution screen is not the way to get more usable space for charts and software, you have to take the screen size, which in turn affects the pixel size, into account.
With the increase in recent years of higher resolution screens the makers of software have had to take them into account and adapt how they do things. Microsoft Windows now has a feature called scaling which it uses to stop your Windows interface and the programs you use becoming unusable due to this tiny pixel issue.
Scaling basically tells your software to increase the size of everything on your screen by a factor based on the size of your screen. You can control this easily through the Windows control panel for your display.
The problem with scaling is two fold:
Firstly, not all programs scale well. What I mean is that some software is not setup to simply scale its output to use a larger number of pixels, instead it stretches elements which leaves you with a really horrible looking interface, it is workable but looks terrible.
This scaling problem is becoming less of an issue though as program makers make changes to their software.
The second and by far biggest problem with scaling is that it uses up a lot more space on your screens.
The whole point for traders by going with a higher resolution screen is to gain more pixels to use, more pixels means more space for charts and programs.
If all your software is scaled by 150% or even 200% in some instances then the amount of free space becomes vastly reduced, how much so?
How Much Space Do You Lose by Scaling Windows?
Windows offers scaling in increments of 25% starting at 100%, so let’s work out how much usable space to lay out your programs and charts is lost by scaling the Windows interface:
|Usable Space Decrease
This means that if you need to scale a 4K screen by 200% then it will end up with the effective resolution the same as a standard FHD screen, despite costing you somewhere in the region of 4 – 6 times the price…
Sure, it would have more pixels, and yes, if your software doesn’t have scaling issues then everything will look ultra sharp and crisp, but you will not be able to fit any more ‘stuff’ on the screen than you could with a standard (and considerably cheaper) FHD screen.
Scaling is a massive consideration and it catches lots of people out.
Working Out Screen Sizes to Avoid Scaling
So, how do you get a high resolution screen without scaling reducing the amount of space you can use? The only ways is to go bigger on the screen.
But how big is big enough (the age old question).
If we assume that the vast majority of people would be able to use a standard FHD (1920 x 1080) screen at a 21.5” size with no problem then we can take this information and make an estimate of the size of each pixel (or technically the space that each pixel has available).
A 21.5” widescreen panel will measure roughly 476mm wide by 268mm tall, this is the dimension of the actual screen not the overall size including bezels / casing around the screen.
We know that an FHD screen has 1,920 pixels across its horizontal axis, so 478mm / 1,920 gives us a result of 0.248mm for each pixel.
So, we now know that if a pixel is 0.248mm in size then it will result in a screen that is perfectly usable for the vast majority of humans.
What we can now do is see how big does a 4K screen need to be to match this, i.e. how physically big does a screen need to be usable and have text / elements appear at the same size as on a 21.5” screen at a 4K resolution?
4K is 3840 x 2160, so if we multiply 3,840 x 0.248mm (our decent pixel size) then we end up with a horizontal measurement of 952mm, this leads to a screen size of 43” (remember that screens are measured across a diagonal and are always listed with inch dimensions).
So, any 4K screen below a 43” size will have smaller pixels than on a 21.5” FHD screen and will have smaller items displayed on it.
You could go for a slightly smaller 4K screen, which would end up with slightly smaller pixels, and still find this usable, it does depend on your eyesight and what you find comfortable working with.
The Size / Resolution Sweet Spots
I’ve mentioned FHD (1920 x 1080) and 4K (3840 x 2160) resolutions a lot so far as these are the two most common and talked about resolutions, but there is another option between them which is called Quad HD or QHD, this resolution is 2560 x 1440 and it is what I personally use.
As it is a lower resolution than 4K you don’t need the screens to be so big, but it is a higher resolution than FHD so you do get more space to play with.
What I have done is to put together a table detailing various screen sizes and the resulting pixel sizes at various resolutions, I’ve colour coded the results as follows:
Green = Usable by anyone without fairly major vision problems without needing any scaling.
Blue = Usable but is edging towards the limit of being too small for some.
Red = Definitely unusable without some amount of scaling.
Purple = Pixels are so big things may start looking a bit ‘blocky’.
|476mm x 268mm
|522mm x 294mm
|553mm x 311mm
|598mm x 336mm
|620mm x 349mm
|708mm x 398mm
|886mm x 498mm
|952mm x 535mm
|1074mm x 604mm
|1218mm x 685mm
*I’ve tried to keep to screen sizes that are actually available to purchase, while a 38″ 4K set may be usable for some people, after 32″ the sizes tend to jump to 40″ or 43″.
What About Ultra Wides?
An UltraWide screen is a fairly new screen type that is really wide, far wider than a normal widescreen, these tend to have different screen resolutions as well to account for the wider display area.
The same rules apply here, we simply need to find out the actual dimensions of the screen, divide it by the resolution and then determine whether the pixels are big enough to avoid scaling issues.
To make things easy let’s look at the two most common resolutions for UltraWide screens, 2560 x 1080 and then 3440 x 1440.
For the 2560 x 1080 panels at 0.248mm per pixel then the screen would need to measure roughly 635mm wide by 268mm high, which in UltraWide dimensions means a diagonal size of 27” or above.
Looking at the higher resolution options of 3440 x 1440 you would need 853mm wide by 357mm tall, which is 36.5” across a diagonal, anything smaller than this is going to result in slightly smaller images on the screen.
Most of the higher resolution UltraWides tend to be at a 34” size which would still be fine for most people without any scaling required.
Personally though I’m not a fan of UltraWides, the only benefit I see is an aesthetic one.
In terms of resolution, 2560 x 1080 wouldn’t make a massive improvement over a standard FHD screen, in fact, two FHD screens side by side would give you an effective combined resolution of 3840 x 1080, resulting in 50% more pixels, whilst costing a lot less to set up.
Even the higher resolution 3440 x 1440 is not as big as two QHD screens which would give you 5120 x 1440 to play with, again almost 50% more usable space, and again would work out cheaper or at worst the same type of cost.
Post Update: We have a new article with a more in depth look at Ultrawide monitors
Further Considerations on Screen Sizes
As you can see from the screen sizes table above, a 40” or 43” 4K screen will not require scaling, it will also give you the same amount of space to lay out programs as four standard FHD screens, on the face of it this sounds like a good option and for some it really will be.
The thing to come back to is that it means sitting in front of a 40” or bigger screen for however long you sit at a computer all day, this is quite a lot of screen to take in.
Personally I find using screens bigger than 27” quite imposing, especially if I have more than a couple of them on my desk. The main problem with bigger screens though is the height of them. I once experimented with four 27” screens arranged in a 2 over 2 (square) configuration, I had neck ache looking at the top two screens within a few days
Using a greater number of smaller monitors allows you to position them where you want them, if you have a top row of screens then these can be angled down towards you, something impossible on a large 40”+ screen.
If you want more space for your charts and software but don’t want to sit in front of a massive screen all day long then you should definitely consider QHD screens.
Two QHD screens at 25” or 27” will still give you over 3.5 times more pixels than an FHD monitor and will be a much easier set of screens to live with on a day to day basis than one giant 4K unit. You could also do this cheaper than the cost of a 43” 4K screen and on the computer side of things QHD is quite a bit less taxing on your graphics setup than a 4K screen.
For traders looking for the absolute maximum amount of space to lay out charts, spreadsheets and data then you could go for multiple 4K screens, it’s certainly possible but you’re probably going to need a bigger desk.
The alternative is to use four QHD screens, at 25” or even 27” you could fit four on a stand, position them wherever you wanted and gain over 7 times the amount of screen real-estate as a standard FHD monitor.
Remember, if you are intending to go for a new 4K screen then make sure it is at least 40”, even a 32” 4K screen will require scaling which at a minimum of 125% will result in a 36% decrease in usable space.
Any scaling at 150% or over and you may as well go for a QHD screen as it would be cheaper and easier to support.
Well that wraps that up, hopefully you have learnt something? If you still need help just let me know below.