After a friend and I were debating the merits of various tablets (iPad, Kindle, etc.) for reading and web browsing, I realized that there was a metric that I hadn’t seen compared between tablets: screen size to weight ratio. So, I took it upon myself to compile a list of a few of the major tablets just to get a sense of what this ratio looks like.

Before we get to the results, let’s be clear about what the goal here is. We are interested in finding a tablet specifically for reading and web browser, with a particular focus on the physical act of reading and hold it in your hand. So, for the purposes here, we don’t care about the details of the OS (which certainly matters!) and just focus on one or two physical attributes.

Imagine your ideally sized tablet to read on—maybe picture a piece of cardboard for the moment. How far away from your eyes would you hold it? What’s the ideal text size? How big is the piece of cardboard? How much can it weigh? The answers to these questions will vary between individuals, but we can deduce a few common answers.

First, most people will have a fixed font size at their ideal reading distance, assuming that the tablet is to be held or placed on the desk in front of them. This means that the size of the tablet is directly proportional to the amount of text that can be displayed on the tablet. Everyone will have a minimum tablet size they will tolerate because if the tablet is too small, it won’t display enough words, and a maximum tablet size because if the tablet is too large, it becomes cumbersome to hold (regardless of weight). If I gave you the exercise to cutout a piece of cardboard at the minimum tolerable size for reading at your ideal distance and font size, it would probably be larger than the iPhone 5’s 6.8 square inch screen. Now, this isn’t to say you can’t read a novel on the iPhone, it just says that it’s probably not ideal.

Second, we would all like that reading surface to be weightless. But, given that it’s not possible, we likely have a range of weight’s that we would tolerate. The current fourth generation iPad’s 662 grams may truly be too hefty for some people to comfortably hold and a read a book.

Finally, I think we can establish that people have a range of tolerances around their ideal reading surface size which include a minimum acceptable tablet size, maximum acceptable tablet size and a maximum acceptable weight. Given that, all else being equal, you’d like to maximum the screen size to weight ratio within those tolerances.

For this chart then I computed weight (in grams) to screen size (in square inches) of various tablets, and threw two phones into the mix just for comparison.

	weight (g)	size (sq. in.)	weight/size	density (ppi)	width (pixels)	height (pixels)
iPad Mini	308	29.6	10.4	163	1024	768
Galaxy Note 8	338	28.7	11.8	189	1280	800
Kindle Paperwhite	213	17.5	12.2	212	1024	768
Galaxy S4	130	10.7	12.2	441	1920	1080
Galaxy Note 10.1	590	46.1	12.8	149	1280	800
Nexus 10	603	45.5	13.2	300	2560	1600
iPad	662	45.1	14.7	264	2048	1536
Kindle Fire HD 8.9	567	35.7	15.9	254	1920	1200
iPhone 5	112	6.8	16.4	326	1136	640
Kindle Fire HD 7	394	21.9	18.0	216	1280	800
Kindle Fire	413	21.5	19.2	169	1024	600

A few observations:

1. The most obvious take home from this chart is that the iPad Mini stands out as significantly better than the competition, while the Kindle tablets are significantly worse. Surprising, to me at least, is that the iPad Mini actually fairs better than the Kindle Paperwhite e-reader.
2. I don’t think that the iPhone 5 or the Galaxy S4 would meet most people’s minimum screen size tolerance for a tablet reading device so I don’t think this metric is particularly relevant, but it is interesting to see how they both fall into the mix.
3. The fourth generation iPad is really quite heavy for its screen size, not impressive at all.

A retina display is arguably the other most important physical attribute one would want from a tablet, yet none of the tablets that score the best weight/size ratio have retina displays. To me, this explains why tablets such as the iPad mini have faired so well—they excel at maximizing the size/weight ratio that tablets with a retina display can’t compete with yet.