Scale font size on android wear to fully utilize screen resolution

I simply want to scale 10 characters of text to use the full screen width using textSize alone. If screen resolution is 100 x 100 and I want 10 characters to fully occupy the screen horizontally, why can't I just use:

 DisplayMetrics metrics = getResources().getDisplayMetrics();
 float pixelFontSize = metrics.widthPixels / 10f;
 textView.setTextSize(TypedValue.COMPLEX_UNIT_PX, pixelFontSize);

? In my testing, I get text that is way to small (uses about 1/3 the resolution) on a 280 x 280 wtih 280 dpi AVD, yet on another AVD 360 x 330 hdpi, the code above produce text way too big to fit on one line. ...I mean, sure I could see needing to subtract a small amount from the pixcelFontSize to account for text layout, but my results are all over the place. I must be missing something. First I was messing with density and the scaled measurement dp and sp, but logic would say that given my problem, density has nothing to do with it at all, right?