Post Hole Calculator
Calculate concrete for post holes
in
in
Formula
Volume = π × r² × depth
Cylindrical volume for each post hole. Concrete fills around the post.
Examples
10" holes, 36" deep, 10 posts
~5.45 ftÂł total, 9 bags of 50lb mix.
Frequently Asked Questions
About Post Hole
Calculate concrete needed for fence or deck post holes. Post holes are cylindrical, so use π×r²×depth for volume. Set posts in concrete for stability—fill the hole around the post, leaving 2-3 inches above grade for water drainage. For fence posts, dig holes 1/3 the length of the post (a 6-foot fence needs 2-foot holes, so use 8-foot posts). In cold climates, dig below the frost line to prevent heaving. Use fast-setting concrete for quicker installation—you can pour dry mix into the hole and add water on top. Let concrete cure 24-48 hours before attaching fence panels or applying load.