Recommended text size ratio between mobile and tablet devices?
android
Solution
Actually we developers need not worry about that ratio. I simply externalize font size values into res/values/dimensions.xml and use sp as a unit.
<resources>
<dimen name="my_font_size">16sp</dimen>
...
Scale-independent Pixels - this is like the dp unit, but it is also scaled by the user's font size preference. It is recommend you use this unit when specifying font sizes, so they will be adjusted for both the screen density and user's preference.
Just saw your edit: Since sp already takes user prefs and dpi into account all you can do is to assign different font sizes via the resource system. And to my knowledge there is no single magic conversion number for tablets to phones. Just think about the multitude of different screen sizes out there. You could however use a custom style which uses one of the theme defined values for text size.
Id like to hope that device manufacturers know which font size has good readability on their devices.
<style
name="MyTextStyle"
parent="@android:style/TextAppearance.Medium">
</style>
Problem
What is recommended text size ratio between mobile and tablet device? There is an app for a mobile device and I need to make the same for a tablet device. If font size in mobile app is 16dp, what should be in tablet app? There must have been some multiplication ration which I can use to best decide on text size for a tablet app. Android design web site does not say much about this. PS. I know that I can tweak each text by testing it on a device, but I am looking for a recommended ratio. EDIT not 16dp, but 16sp. Sorry!