How much concrete per fence post?
Calculate the hole volume. Then, subtract the post volume below ground.
A 12 in diameter hole that is 30 in deep uses approximately 1.75 ft³ around a 3.5 in square post.
| Hole size | Concrete volume | Cubic yards |
|---|---|---|
| 10 in x 24 in | 0.92 ft³ | 0.034 yd³ |
| 12 in x 24 in | 1.40 ft³ | 0.052 yd³ |
| 12 in x 30 in | 1.75 ft³ | 0.065 yd³ |
| 12 in x 36 in | 2.10 ft³ | 0.078 yd³ |
| 14 in x 36 in | 2.95 ft³ | 0.109 yd³ |
The table uses a cylindrical hole and a square post. Add more material after you calculate the volume.
Calculate the concrete volume
For a cylindrical hole, multiply 3.1416 by the radius. Multiply this result by the radius and the depth.
Use feet for each value.
Multiply the post width by the post width and the hole depth. Subtract this post volume from the hole volume.
Hole dimensions
The hole diameter and depth control most of the concrete quantity. If the hole sides are not uniform, measure the hole.
The QUIKRETE post-setting instruction gives a hole width that is three times the post width. Local conditions can make other dimensions necessary.
All fence posts
Multiply the concrete volume for one post by the total post quantity. Include line posts, ends, corners, and gate posts.
Add more concrete for irregular holes and spillage. Do not decrease a specified hole dimension.
Concrete bag quantity
Divide the total cubic feet by the yield on the bag. Use the fence calculator or read How many bags of concrete per fence post?
Important information
- Use the measured post width. Do not use the nominal size.
- Use the specified hole depth and diameter.
- Read the mixing and placement instructions on the concrete bag.