Font and size of text outside and inside of a WebView

I will display text inside and outside (normal Label, ListView and others) of a WebView with the same font and size. How can I synchronize the size, so that text inside the WebView looks identical to text outside of the WebView when the content in the WebView isn't zoomed? It is clear, that the size could be changed by user, when s/he zooms the content of the WebView. But in the beginning, it should be the same. Need this for iOS and Android, but would be good to know this although for WinPhone.

Thank you.