Post Hole Concrete Calculator

How much concrete do I need for a post hole?

posts
in
ft
Post size
Bag

Order this much fast-setting concrete

2850 lb bags

Hole volume minus the post, with 10% extra, at about 0.375 cu ft per bag. Set depth from your frost line and local rules.

2 ft deep10 in hole10 posts
Concrete per post0.92 cu ft
Bags per post2.7
Total concrete10.1 cu ft

Set hole size and post size and see the bags per post. The post displaces real volume, so it is subtracted from the hole.

How it works

Hole volume minus post volume, plus 10%, divided by your bag yield. A 50 lb fast-setting bag is about 0.375 cubic feet.

Before you order

  • Dig the hole wider at the bottom where soil allows, which improves resistance to uplift.
  • Slope the concrete top away from the post so water does not sit against the wood.
  • Brace posts plumb before you pour, since fast-setting mix firms up within minutes.

Common questions

How many bags of concrete per fence post?

A 4 × 4 in a 10 inch hole 2 feet deep takes about 2.5 of the 50 lb fast-setting bags.

Does fast-setting concrete need mixing?

Many products are poured dry and watered in the hole. Follow the instructions on your bag.