Concrete for Fence Post Calculator
How much concrete per fence post? Enter your post count, hole size, and post dimensions — we'll subtract the buried post volume and give you bags per hole plus the total.
You need about
— 80 lb bags total
- Per post: — bags
- Total cubic feet: —
How the fence post concrete calculator works
A post hole is a cylinder: volume per hole = π × (diameter ÷ 2 ÷ 12)² × (depth ÷ 12).
We subtract the buried portion of the post, multiply by the number of posts, then divide by
0.60 — one 80 lb bag — and round up.
A common rule is to set posts one-third of their height into the ground and dig the hole three times the post width. For a 4×4 post, a 12-inch hole is typical; a 6×6 needs about 18 inches.
Assumptions and sources
The calculator assumes the post is fully buried for the entered depth and uses a standard 80 lb bag yield of 0.60 cubic feet.
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Last updated: 2026-09-09