Recommended button sizes
When creating a mobile game, pretty much all of your interactions are controlled by button and screen taps. Buttons that are a reasonable size on a PC or console game may be too small for a mobile game. Therefore, you’ll want to make sure to design your buttons so that they are still visible on the smaller screen and large enough to be touched by a finger.
Apple, Google, and Microsoft all have specific recommendations for the size of a button’s touchable area when designing for their devices. Apple recommends that buttons be 44 points x 44 points. Google recommends 48 dp x 48 dp with 8 dp spacing between two buttons. Microsoft recommends 9 mm x 9 mm with 2 mm padding between two buttons.
You can find information about designing touch/hit areas for each mobile platform at the following locations:
