Concrete for Fence Posts Calculator
How many bags of concrete to set every post in your fence.
Concrete
- 80 lb bags
- 34
- or 50 lb bags
- 55
- Concrete volume
- 20.26 cu ft
- Gravel base
- 6 cu ft
- Posts
- 22
- All posts: 22 × 10" Ø × 24" deep → 0.92 cu ft each
How this was calculated
- Holes 10" Ø × 24" deep (⅓ of height, min 24") over a 6" gravel base. 80 lb bag ≈ 0.6 cu ft.
Planning estimate only — not a contractor quote. Actual pricing varies by location, terrain, material quality, permits and project complexity.
How much concrete per post
A 4×4 wood post in a 10" × 24" hole needs about 0.95 cu ft of concrete — about 1.6 bags of 80 lb or 2.5 bags of 50 lb. Taller fences need deeper holes and more concrete. Add 6" of gravel at the bottom for drainage.
| Post | Hole | 80 lb bags / post |
|---|---|---|
| 4×4 wood, 6 ft fence | 10" × 24" | ~1.6 |
| 4×4 wood, 8 ft fence | 10" × 32" | ~2.1 |
| 5×5 vinyl, 6 ft fence | 12" × 24" | ~2.2 |
| 2⅜" chain link | 8" × 24" | ~1.1 |
See the full method in how much concrete per fence post.
Frequently asked questions
Fast-setting or regular concrete?
Fast-setting mix is poured dry and watered in the hole, which is easier for DIY. Regular mix is cheaper and slightly stronger when mixed properly.
How big should the hole be?
Roughly three times the post width in diameter — about 10 inches for a 4×4 — and one-third of the fence height deep, minimum 24 inches.