The average laptop screen is about 17 inches wide, but the screens on many laptops are only 13 inches wide. That’s because most laptop manufacturers make them in two different sizes: a 13-inch model and a larger 17-inch model. But there’s no good reason for this. Laptop screens are usually made of two different types of glass: an anti-glare type for use in bright sunlight and a regular type for use in normal light. The regular type of glass is usually wider than the anti-glare type, so the manufacturer can fit more of it on the screen without having to make the screen smaller. But there’s no good reason why laptops have to be divided into two sizes. If all laptop manufacturers made their screens the same size, people who want a 17-inch laptop would just have to buy a bigger laptop instead of settling for a smaller one that doesn’t fit their needs. ..

Have you ever wondered why laptop screens seem to come in such odd sizes? Then you are not alone! Today’s SuperUser Q&A post looks at the reasons for the odd screen sizes you see when comparing laptops.

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.

Photo courtesy of Jace Cooke (Flickr).

The Question

SuperUser reader TheCleaner wants to know why laptop screens come is such odd sizes:

Why do laptop screens come in such odd sizes?

Why do laptop screen sizes come in the fractional sizes they do instead of 11/12/13/14/15″? The most frequent ones I see advertised are 11.6″, 12.5″, 13.3″, 14″, and 15.6″. What is the reasoning behind it? Keyboard size? Ergonomics? Resolution requirements? Most are LCD screens just like television sets, and yet televisions are advertised as whole numbers (19″, 26″, 46″, etc.).

Looking at actual LxWxD dimensions on laptops does not really help since screen bezels vary in size.

For instance, this example: 11.6″ laptop dimensions = 11.55″ x 8.50″ x 1.27″ — this is due to a rather large bezel.

Whereas my x1 carbon touch has a 14″ diagonal screen, but its dimensions are equal to a WQHD Touch: 13.03″ x 8.94″ x 0.55″ (Front), 0.79″ (Rear) — again bezel. If it could be edge to edge, that would be different, and “normal math” would insist the actual “monitor size” was about 15.5″, which it is if you include the bezel.

So:

Are there actual equations/ratios/mathematical factors in determining screen sizes on a laptop that make certain sizes more common than others? Note that I stated screen size (like the common 11.6″, 13.3″, 15.6″, etc.) and not actual dimensions of the monitor lid itself.

To Help Clarify The Question:

I am asking why those particular fractional sizes are so common? Look at HP, Lenovo, and Dell. They all tend to go with those screen sizes. Is it because it is what the consumers are used to seeing or using? Is it dictated by resolution requirements that ‘control’ the screen size (meaning 11.6″ works out resolution-wise, but 11.7″ does not)? Or is it something else? If you want to hone in on one: Something, somehow determined that 11.6″ was a good common screen size…I am curious what that was.

The Answer

SuperUser contributor Adam Davis has the answer for us:

Enjoying the debate? Then browse on over to the original thread via the link shared below to see even more awesome answers and discussions about laptop screen sizes!

The manufacturing plant starts off with a single slab of glass on which the displays will be manufactured. Mother glass sizes are mostly standardized in the industry, and are increasing:

The larger a piece of mother glass is, the harder it is to work with due to breakage. However, throughput is counted by the number of working displays at the end of the line, and certain line processes take the same amount of time for a small piece of glass as for a large one. So to increase throughput, increase the mother slab and put more displays on it.

It does not make sense to create a manufacturing line for a single size of display. It makes more sense to create a manufacturing line that handles the same size mother glass slab, and just change the number of displays created from the mother glass slab based on the order requirements.

Since the manufacturing line glass is not going to change in size, once you know the size of the display you want, you can determine how many of them can fit onto one mother slab. If there is additional space, it makes sense to increase the size until you are using as much space on the slab as possible, without going over your size requirement.

So the 10th generation glass will make one 150″ TV (which is only used at tradeshows simply to showcase the size of the mother glass a given factory can handle), or it will make nine 50″ TVs. The second generation glass was able to make a nice 24″ desktop display, or four 11.6″ displays.

A more in-depth treatment of this can be found at Norm’s Flat Panel. AUO has a nice interactive diagram that shows cutting patterns for a few sizes up to generation 8.5 glass. While I included 11th generation size, there are no plants currently operating at this size. It is expected the first such plants will open in 2015 or 2016, and they may use mother glass somewhere between 10th and 11th generation. Keep a watch for the next tradeshow as other manufacturers demonstrate 150″ TVs to show off their new 10th generation plants, and eventually 180″ TVs as the first 11th generation plants come online.

Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.