Bags of concrete per fence post
| Hole diameter | Hole depth | Concrete | 80 lb bags | 60 lb bags |
|---|---|---|---|---|
| 8 in | 2 ft | 0.7 ft³ | 2 | 2 |
| 10 in | 2 ft | 1.1 ft³ | 2 | 3 |
| 10 in | 3 ft | 1.6 ft³ | 3 | 4 |
| 12 in | 3 ft | 2.4 ft³ | 4 | 6 |
| 12 in | 4 ft | 3.1 ft³ | 6 | 7 |
The chart doesn't subtract the post itself, so it includes a little extra. A 4 × 4 post takes up about 0.17 cubic feet in a 2 ft hole. For a whole fence, including posts, rails and pickets, use the fence calculator.
How big should the hole be?
A common rule is a hole three times the post width, so about 10 inches for a 4 × 4 and 18 inches for a 6 × 6. Dig one third to one half of the above-ground height, and below the frost line where the ground freezes.
Frequently asked questions
Can I use fast-setting concrete for fence posts?
Yes. Fast-setting mix is poured dry into the hole and then soaked with water. It uses about the same number of bags and sets in 20 to 40 minutes.
Should concrete go to the top of the hole?
Stop an inch or two below ground level and slope the top away from the post so water runs off, then cover with soil or gravel.
Last reviewed: 2026-10-31