I plan to step up this year to a screen that mea­sures at least 4.7 inches in diag­onal, from the 4-​​inch iPhone I use today. With smart­phones, even a little increase is a big deal.

We used to laugh at Gordon Gekko’s giant cell­phone in “Wall Street,” but handset makers are back to super­sizing phones—or at least their screens. The Sony Xperia Z Ultra is about the size of an “XL” Hershey’s bar, with a 6.4-inch screen. In the past year, the “phablet” has gone from a joke to a best-​​seller.

But what’s the ideal size?

I tested a dozen phones and con­sulted ergono­mists, phys­ical ther­a­pists and count­less pants pockets. It turns out, there is some sci­ence to fig­uring out what screen size might best serve you, and three fac­tors that matter most: What you can see, what your thumbs can reach and what you can com­fort­ably hold. (Com­pare how dif­ferent phones will fit in your hand in an interactive.)

The tricky part: “It’s all trade-​​offs,” says Jack Den­ner­lein, a pro­fessor of ergonomics at Har­vard and North­eastern University.

Read the article at The Wall Street Journal →