While the usual guideline is around 12% bodyfat for men, this shifts up and down depending on the sheer muscle mass of your abs. The stronger and bigger your abs, the higher bodyfat-% you can get away with. This is because the impression they make on the skin is determined by the sheer size. You don’t need to be as lean if you’ve got massive abs – especially if they’re toned due to regular use. Aim for the 12% mark regardless, and you’re likely to see what you’re working with. If you’re particularly weak or strong in the core, you can adjust expectations up and down a few %.