Do we sacrifice consistency and clarity for the sake of convention?

We are familiar with size numbers for shoes, hats, dresses and so on. Ronnie Cohen looks at the convention for screen sizes based on inches and asks if this really makes sense.

I recently came across an article with the title “The new lap of luxury” in the London Life section of the London Evening Standard. This article about laptops appeared on page 35 of the paper and was published on Thursday 13 July 2017. It is an article about Microsoft Surface laptops that aims to challenge Apple’s popular MacBook. The subtitle of the article, at the top of the article, says “Slimmed down, speedy and supercharged – the Microsoft Surface is here to challenge Apple’s computers”.

It followed the convention of giving width, height and depth in centimetres and screen sizes in inches. As the screen size of a folded laptop has a width and height that is almost the width and height of the laptop, one would think that it made more sense to express screen sizes in centimetres for consistency. However, screen sizes are expressed in the UK as so many inches from one corner of the screen to the opposite corner.

One feature of the printed version that does not appear in the online version is the specifications of “The Winning Laps” as the article describes them. Two laptops are shown with their specifications in that part of the printed article, one Microsoft Surface laptop and one MacBook Pro laptop.

The size of the Microsoft Surface laptop is given as 30.8 cm x 22.3 cm x 1.45 cm. The screen size of this laptop is given 13.5 inches.

The size of the MacBook Pro laptop is given as 30.4 cm x 21.2 cm x 1.49 cm. The screen size of this laptop is given as 13.3 inches.

The Evening Standard followed the accepted UK convention of giving laptop sizes in centimetres and screen sizes in inches. Apparently, since the appearance of monitors, laptops, tablets, mobile phones and digital cameras over the past 30 years, few have asked why two incompatible systems are often used for describing the dimensions of the device and its screen size. Size is one physical phenomenon. Using one system would make comparisons easier by letting us just compare the numbers rather than think about conversions from centimetres to inches or inches to centimetres.

Of course, globally there are many countries where inches mean nothing. The screen size in inches is merely a number, its derivation lost in the mists of time, as with sizes of clothing and shoes. But this system of screen sizes, whether inches or centimetres, is consistent around the world thanks to ISO, and for this we should be thankful, even if we have to check the product description or specification to find out how big it really is.

You can read the online version of this article at:

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4 Responses to Do we sacrifice consistency and clarity for the sake of convention?

  1. Daniel Jackson says:

    I think we need to introduce the topic of actual measurements versus trade descriptors. The dimensions they are giving you in centimetres are actual measurements, the dimensions in inches are trade descriptors. Trade descriptors don't have to match the measured value and in most cases they don't. More often than not, the size is inflated.

    Trade descriptors benefit the manufacturer in that they can change the size and not change the description. Consumer groups in the US a number of years ago found this practice to be deceptive when describing TV screens and monitors and filed a lawsuit in court. The television manufacturers argued that they were trade descriptors and not real measurements. The outcome of the lawsuit forced the manufacturers to make it clearer that the screen sizes were actually trade descriptors. All they did was add the word "class" to the description.

    Presently in the US there is another group of people suing a number DIY stores over the marketing of 2 x 4s. These are supposed to be 2 in x 4 in (50 mm x 100 mm) pieces of wood, but they are smaller, about 40 mm x 90 mm. Some consumers feel they are being deceived even though industry experts insist it is an old practice and everyone in the trade is aware of the short measure.

    Those living outside the US who use metric units daily would never be aware that these odd numbered trade descriptors are somehow connected to measuring units, thus no one in a metric country would ever notice anything odd or deceptive to initiate a complaint. Only in the US and among metric opposers in the UK would one expect someone to notice.

    If they want to use trade descriptors, that would be fine, but at least include the correct metric value for the whole world to compare.

  2. Han Maenen says:

    Once I read an ad about a '24 inch' screen, but in the accompanied text the screen size was given as 23.6 inches. 0.4 inch is equals 1 cm. This means that the real dimension of the screen is 60 cm. I think that this nonsense is the work of marketeers. So, my screen measures 60 cm. I have seen screen sizes described as 24' in a shop where I live. Sure, 24 feet, I will need a lorry to get it home. They accept this non-metric size and they do not know the correct symbols for foot and inch. Two more howlers I found in ads or shops: ' 24" inch ' and even ' 24' inch '!

  3. Daniel Jackson says:


    The true size of that 23.6 in screen is exactly 600 mm. 600/25.4 = 23.622 047..... When rounded it becomes 23.6. Another popular size is the 800 mm, hidden under the trade facade of 32 in class, but in fine print 31.5 in which is hidden metric for 800 mm.

    This is what is known as hidden metric.

  4. Michael Glass says:

    The problem with screen sizes is not whether they are expressed in inches or centimetres or millimetres, but that these sizes are based on the diagonal measurements of the screens.

    If all screens were the same shape, this would be no problem, but screen dimensions vary, from very nearly square to quite elongated rectangles. Therefore the size of screen does not bear a constant relationship to the area of the screen. Even worse, the area of the screen is the square of the diagonal measurement, and this masks the fact that the larger screen is more expensive to run. (Of course, this only applies if everything else is equal.)

    Here are some examples:

    Double the screen size and it won't cost you double to run it. It will take four times the power to run the screen.

    An 11 inch screen will take 21% more power to run than a 10 inch screen (not 10% as some might be led to believe).

    A 70cm screen will take about half of the power to run compared with a 100cm screen.

    I think the best thing to do is to ditch the diagonal measurement and use the total area of the screen as the measure.


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