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Viktor
Viktor

Reputation: 480

Define and calculate Apples definition of the unit point

Apple writes in the user interface guidelines that a tappable element should be at least 44 x 44 points. They provide an example of the calculator app for reference. When I measured the tappable buttons I got the height of 10 mm/38 px. Using tools I found online I converted this to approximately 29 postscript points.

My question is what does Apple mean by 44 points? How do I convert this correctly?

Upvotes: 0

Views: 1660

Answers (2)

bryfox
bryfox

Reputation: 301

Apple's use of 'point' is not the same as a typographical point. It's an abstract unit that doesn't have a fixed correlation to pixels, nor to any physical measurement (e.g., millimeters).

The first part of that is easy to see; a point width on a retina iPhone covers two pixels, twice as many as on a non-retina iPhone.

The iPad Mini makes the second part of that first statement pretty clear. From an iOS developer's point of view, 44 points is the same measurement on an iPad 2 as it is on the mini. But to a user, those represent very different physical (millimeter) sizes.

There's a bit more written under Points vs Pixels in their drawing guide.

It does seem a bit strange for the HIG to prescribe sizes that don't correspond to, well, humans. In practice, for a UX designer, your approximations are probably fine.

Upvotes: 3

Mr Lister
Mr Lister

Reputation: 46569

A point is 1/72 of an inch, so 44 points is 0.6 inch or 1.5 cm. I don't think Apple can change this definition all by themselves.

Upvotes: -1

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