Post Hole Concrete Calculator

Setting fence posts or deck footings goes a lot smoother when you know how many bags of concrete the holes will swallow before you head to the store. Estimating the count accurately means you don't haul home a pallet of leftovers or stall the job halfway through for a second trip. In 2026, with both material prices and labor time under pressure, that kind of upfront planning has a real effect on how quickly and cheaply a project wraps up.

Because a post hole is essentially a cylinder, the volume comes from V = π * (r^2) * h, where r is the radius (half the hole's diameter) and h is the depth. That figure is converted to cubic feet and divided by the yield of a standard bag: a 60lb bag covers about 0.45 cubic feet in 2026 and an 80lb bag about 0.60 cubic feet. The total is then rounded up to the next full bag so you're never left a scoop short.

Rounding up is deliberate, since holes are rarely perfectly straight, some mix is always lost to spillage, and yields drift a little from bag to bag. Those yields also shift by manufacturer and mix type, so it pays to read the figure printed on the bag you actually buy. The error that bites most often is shorting the depth, which leaves you with too little concrete and a footing that won't hold the post the way it should.