Concrete Per Fence Post Calculator
Calculate the concrete to set a fence post, the hole volume, cubic feet and how many 80, 60 or 50 lb bags you need per post and for the whole fence.
This free concrete calculator for fence posts works out the hole volume and how many bags of concrete each post takes, plus the total for the whole fence. Enter the post width, hole diameter and depth, pick your bag size, and get the count. It answers how many bags of concrete per fence post you need. Runs in your browser, no sign-up.
Read the guide: How Much Concrete Per Fence Post?Concrete per post
Bags per post
3
1.35 ft³ of concrete per hole
- Bags for all posts
- 42
- Total concrete
- 18.89 ft³
That is the hole volume minus the post. Mixing a touch extra is wise, concrete settles and a part-filled last bag is normal.
For fast-setting or gravel-base methods the volume differs. Always set below your local frost line.
How it works
- 1
Size the hole
Enter the post width, hole diameter and depth. A good rule is a hole three times the post width.
- 2
Pick a bag
Choose the bag size you are buying, 80, 60 or 50 lb.
- 3
Get the bags
See the cubic feet and bag count per post, then for every post in the run.
Instant & 100% private — nothing is uploaded
Every calculation runs locally in your browser. The income, balances and goals you enter stay on your own device and are never sent to a server — nothing is stored, logged or shared.
Frequently asked questions
- How much concrete per fence post?
- It is the hole volume minus the post. A 4×4 post in a 12-inch hole dug 2 ft deep takes roughly 1.3 cubic feet, about three 80 lb bags. Bigger holes need more.
- How deep should the hole be?
- Set posts about a third of their above-ground height deep, and always below your local frost line. Two to three feet is common.
- Which bag size is best value?
- An 80 lb bag yields about 0.6 ft³, a 60 lb about 0.45, a 50 lb about 0.375. Fewer big bags usually means less mixing, the calculator shows the count for each.
- How accurate is the concrete estimate?
- The hole volume and bag count are exact for the dimensions you enter. Real holes are rarely perfect cylinders and a bell-shaped bottom uses more, so round up and keep a spare bag on hand rather than running short mid-set.
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