How Much Concrete Do You Need Per Fence Post?
Part of Decks, Fences & Roofing
Quick answer
For a typical 4×4 post in an 8–10 inch wide hole dug one-third the post height, use 1–2 × 50 lb bags of fast-setting concrete per post.
The right amount depends on hole diameter and depth. A wider or deeper hole — needed for taller fences or loose soil — uses more concrete.
| Hole size | 50 lb fast-set bags per post |
|---|---|
| 8 in wide × 2 ft deep | 1 bag |
| 10 in wide × 2.5 ft deep | 2 bags |
| 12 in wide × 3 ft deep | 3 bags |
Bury at least one-third of the post for stability, and more in windy areas or for gate posts.