Well by the standards of this board I guess I don't have big arms. Right now my right arm is measuring exactly 18" flexed and my left is measuring 17.75" flexed. My right forearm is exactly 13" flexed and my left is a pitiful 12.5" flexed.
I've seen guys with smaller arms than that, and huuuge forearms. One thing for sure is that I get this genetic trait from my dad, he also has small forearms