How Much Concrete for a Fence Post?
A typical fence post set in a 10 inch wide, 24 inch deep hole needs roughly one to two 50 lb bags of concrete mix, depending on post size. Size the hole at about three times the post width and a third of the post height deep, then subtract the post itself when estimating concrete.
Sizing the hole
A common rule is to make the hole about three times the post's width and to bury about one third of the post's above-ground height. A 4x4 post in a 10 inch diameter hole, 24 inches deep, is typical.
Use the concrete calculator's round option: enter the hole diameter and depth to get the volume, then the bag count for your bag size.
Bags per post
A 10 inch by 24 inch hole is about 0.9 cubic feet before subtracting the post, so roughly two 50 lb bags (0.375 cu ft each) or one and a half 60 lb bags.
Mixing several posts? Multiply per-post bags by the number of posts and add a little extra. Past a dozen or so posts, consider ready-mix or a faster set product.
FAQ
How many bags of concrete for a fence post?
Usually one to two 50 lb bags per post for a typical 10 inch wide, 24 inch deep hole. Larger posts and deeper holes need more.
How deep should a fence post hole be?
About one third of the post's above-ground height, and roughly three times the post's width in diameter.