Recently i brought a Android phone for my father and he complained the default font size are small, browsing web site is not a problem caused can use zoom in and out function but Android system setting function is so hard for him, sometimes tap wrongly. I went through Android Market finding a change font size Android apps but most of apps need Android phone rooted,finally i found a Android app that no need phone rooted,that is 「Big Font (change font size) 」.
Install Big Font
Big Font (change font size) app working for Android 2.3 or above devices.The default font size is 「Normal 」as start running 「Big font 」. As swipe right can adjust font size to 110%,115% and 130%, decrease font size to 85% and 90% swipe to left, remember tab 「Apply 」 after select your prefer font size.

Below are the screen shot for default and 130% font size.
Features are :
- scale system font size from 85% to 130%
- preview the scaled text before applying
- show a notification icon describing the current font size. An option is also provided to hide it
- switch system font size via tapping the notification
- customized the scaling value (will be released in next version)
- Android 4.x (Ice cream sandwich) only provides 3 scaling values, we provide more
- for Android v2.3~3.x users. You can add “not working” apps into the ignored apps list
Download Big Font (change font size) from Android Market.
Works great but only on Gingerbread and above. It needs to work on version 2.1 devices and above.