Calculate the number of concrete bags needed for fence posts or deck footings.
Post & Hole Dimensions
Concrete Requirements
Setting Posts?
Enter your post and hole dimensions to see how much concrete you need.
About this calculator
Overview
This calculator helps you determine exactly how much premix concrete you need to set fence posts or deck footings. It subtracts the volume of the post itself from the hole volume to give a precise estimate.
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Pro Tips
Add about 6 inches of gravel at the bottom of the hole for drainage before pouring concrete.
Slope the top of the concrete away from the post to shed water and prevent rot.
Most premix concrete yields about 0.45 cubic feet for a 60lb bag and 0.60 cubic feet for an 80lb bag.
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Fun Facts
"A standard 4x4 wood post is actually 3.5 x 3.5 inches."
"Post holes should generally be 3 times the width of the post."
"Frost line depth varies by region; ensure you dig deep enough to prevent frost heave."
Formula: Volume = (Hole Volume - Post Volume) × Number of Posts
