How big should touchable area be? [closed]

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I am porting a web app to a mobile app using phonegap. In it there is a window control that is resizable similar to windows in Windows, i.e. clicking the edge and dragging.

My initial thought is to simply translate touch events to mouse events, and when doing this I notice that the edges, i.e. the touchable area need be rather big in order to be able to hit it with a touch.

I am wondering how big should an area be in order to conveniently be able to touch it? My second solution is to build the resize using pinch zoom or something else.

Answer 1

48dp.

http://developer.android.com/design/style/metrics-grids.html

Why 48dp?

On average, 48dp translate to a physical size of about 9mm (with some variability). This is comfortably in the range of recommended target sizes (7-10 mm) for touchscreen objects and users will be able to reliably and accurately target them with their fingers.

If you design your elements to be at least 48dp high and wide you can guarantee that:

your targets will never be smaller than the minimum recommended target size of 7mm regardless of what screen they are displayed on. you strike a good compromise between overall information density on the one hand, and targetability of UI elements on the other.