Concrete bags per post hole by post & hole size
Typical industry planning values — NOT a structural/geotechnical design. Frost depth, soil, wind load and local code set the real post depth and footing; check your local building department and call 811 to locate utilities before you dig. A licensed engineer sizes load-bearing or high-wind fence posts.
Concrete per hole is the hole volume minus the post: bags per post = ceil((π·r²·h − post) ÷ bag yield). Yields are labeled typicals — a 40 lb bag ≈ 0.30, a 60 lb ≈ 0.45, an 80 lb ≈ 0.60 ft³. Confirm the yield on your bag. Use this with the concrete-per-post calculator and the post-hole depth reference.
| Post / hole | 40 lb | 50 lb | 60 lb | 80 lb |
|---|---|---|---|---|
| 4×4 post, 10" × 24" hole | 4 | 3 | 3 | 2 |
| 4×4 post, 10" × 30" hole | 4 | 4 | 3 | 2 |
| 6×6 post, 12" × 30" hole | 5 | 4 | 4 | 3 |
| 6×6 post, 12" × 36" hole | 6 | 5 | 4 | 3 |
Bags per one post hole (multiply by your post count). Yields are labeled typicals — a 40 lb bag ≈ 0.30, 50 lb ≈ 0.375, 60 lb ≈ 0.45, 80 lb ≈ 0.60 ft³; confirm on your bag.