Post Hole Concrete Calculator

About this calculator

This calculator finds the concrete volume for a cylindrical post hole — hole volume minus the post's own volume — then converts that to the number of pre-mixed concrete bags needed, using each bag's standard yield (a 50 lb / 25 kg bag typically yields around 0.017–0.02 cubic meters, or about 0.6 cubic feet, once mixed).

Fence installers, deck builders and DIYers use it before a single trip to the hardware store, since underestimating bags means a wasted second trip and overestimating wastes money — the rule of thumb of "hole diameter three times the post width, depth one-third to half the post's above-ground height" is what drives the volume this calculator works from.