How many bags of concrete per fence post?
Divide the concrete volume for one hole by the yield on the bag. If the result is not whole, increase it to the next whole number.
One 12 in diameter hole is 30 in deep and contains a 3.5 in square post.
For this hole, three 80 lb bags or four 60 lb bags are necessary.
| Hole size | 80 lb bag at 0.60 ft³ | 60 lb bag at 0.45 ft³ |
|---|---|---|
| 10 in x 24 in | 2 bags | 3 bags |
| 12 in x 24 in | 3 bags | 4 bags |
| 12 in x 30 in | 3 bags | 4 bags |
| 12 in x 36 in | 4 bags | 5 bags |
| 14 in x 36 in | 5 bags | 7 bags |
Bag yields can be different. Use the yield on the product label.
Calculate the bag quantity
- Calculate the cylindrical hole volume in cubic feet.
- Subtract the post volume below ground.
- Divide by the concrete yield for one bag.
- If the result is not whole, increase it to the next whole number.
Bag weight and bag yield
Bag weight and concrete yield are different values. A heavier bag usually gives more concrete.
Read the yield on the bag. Put that value in the calculator.
Project quantity
Calculate the total concrete volume for all posts. Then, calculate the bag quantity.
This method can give fewer bags. Keep sufficient material at each hole.
Hole and post sizes
A larger hole uses more concrete. Use How much concrete per fence post? for the volume formula. The fence calculator calculates the project bag quantity.
Important information
- Use the yield on the selected concrete product.
- Add more material for irregular holes and spillage.
- Keep the specified hole dimensions.