Post diameter depends on the strength of the fence. Gerrish says the lightest-duty fence, such as a 1- or 2-wire, high-tensile pasture subdivision fence, only requires a 4- to 5-inch-diameter post. A 5-strand barbed wire fence, or 5- or 6-strand high-tensile fence, requires a 6- to 7-inch-diameter post. For net wire fences, Gerrish recommends an 8-inch-diameter post. Keeping corner posts in the ground is Derynck’s chief concern.