The two most common brands of kosher salt, Morton and Diamond Crystal, are shaped differently and have different volume measures relative to standard table salt for the same amount of sodium. Diamond Crystal has—no surprise—a crystal shape, and Morton has a flake shape. One tablespoon of standard table salt has the equivalent sodium to 2 tablespoons of Diamond Crystal kosher salt or 1 1/2 tablespoons of Morton kosher salt.
Board Link: kosher salt
I’ve always had an intuitive sense that regular table salt is more compact than kosher salt. Now I’ve switched to using sea salt the volume of which is probably significantly less dense than even kosher. In this way, I control the saltiness of my dishes more carefully–I think I’m actually cutting back on my salt consumption somewhat. For salting dishes that where the crystals don’t get a chance to dissolve, I determine whether the crunchiness of the crystals will add to the dish, if not, I use a the table salt instead.