Post Hole Concrete Calculator
Enter your hole size, post size, and number of posts to estimate the concrete volume and the number of bags needed to set your posts.
Results
- Bags per hole
- 2 bags
- Total bags
- 9 bags
- Concrete per hole
- 0.87 cu ft
- Total concrete
- 5.21 cu ft
Estimates only. Round up and buy a little extra to account for waste, spills, and breakage.
Enter your hole size, post size, and number of posts to estimate the concrete volume and the number of bags needed to set your posts.
How to use the post hole concrete calculator
- Enter the number of posts.
- Enter the hole diameter in in.
- Enter the hole depth in in.
- Enter the post width in in.
- Enter the bag size.
- Optionally add a price to estimate the total project cost.
- Read your quantities instantly — no sign-up, and you can print the estimate to take to the supplier.
Worked example
Inputs
- Number of posts
- 6
- Hole diameter
- 10 in
- Hole depth
- 24 in
- Post width
- 4 in
- Bag size
- 80 lb bag (0.60 cu ft)
Results
- Bags per hole
- 2 bags
- Total bags
- 9 bags
- Concrete per hole
- 0.87 cu ft
- Total concrete
- 5.21 cu ft
Using the example values above, the post hole concrete calculator returns 2 bags (bags per hole). Change any field to match your own project and the numbers update instantly.
Formula
Hole volume = π × (diameter/2)² × depth. Subtract post volume. Bags = concrete volume ÷ bag yield, per hole × posts.
Frequently asked questions
- How many bags of concrete per fence post?
- A typical 4×4 post in a 10-inch hole 24 inches deep needs about 1–2 bags of 80 lb concrete. Wider or deeper holes need more.
- How deep should a post hole be?
- Set posts at least one-third of the post's above-ground height deep, and below your local frost line — commonly 24–36 inches.
- Do I need gravel at the bottom of a post hole?
- Yes — add 4–6 inches of gravel for drainage so water doesn't pool around the post base and rot or heave it.
Related calculators
Fence Calculator
Plan posts, rails, and pickets for a wood fence.
Concrete Calculator
Estimate cubic yards, bags, and cost of concrete for slabs, footings, and columns.
Concrete Cost Calculator
Estimate the total cost of concrete by entering a price per cubic yard.
Excavation Calculator
Estimate dirt volume, tons, and truckloads to excavate or haul.