Smallest button size on the touch screen

Question

I am involved in writing a touch screen application for a medical device. The program is similar to a kiosk because the Start menu, etc. It will not be available to the user, and the user will use the on-screen keyboard to enter any text in the rare case that they need. The spec screen size is 1280x1024.

The question is: what is the minimum button size for a reasonable interface? I think that the American penny is a reasonable minimum size in all directions, and the reasoning is that the penny is about as small as we can expect people to feel with their fingers (it has a diameter of 17.91 mm, according to the almighty Wikipedia).

Or a little smaller on larger sizes?

EDIT: some additional knowledge about our users. They must have both hands due to the nature of the device, and gloves will not be worn on them. They would have to be able to manipulate cassettes up to 14x17 inches (again, due to the nature of the device), so I feel pretty confident that they have some kind of manual dexterity.

Answer 1

There are many factors in this that may require the buttons to be much larger.

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