How to use it
- Enter the hole diameter in inches.
- Enter the depth in feet.
- Enter the number of holes you need.
- Click Calculate to see cubic feet, cubic yards and bag count.
What it does – The calculator turns the diameter, depth, and quantity of post holes into three practical measures: total cubic feet, total cubic yards, and the exact count of 80‑lb bags of mix. Why it matters – Knowing the bag count prevents over‑buying (which wastes money) or under‑buying (which stalls a project). The result uses the industry standard that one 80‑lb bag fills about 0.6 ft³, then aggregates the volume for all holes and converts to yards (1 yd³ = 27 ft³). How to read it – The cubic‑feet figure shows raw volume, cubic‑yards is the same volume in larger units for ordering bulk, and the bag total tells you how many bags to order. Round up slightly to cover spillage and settling. You can also adjust the result for a 5 % waste factor directly in your ordering sheet. The tool updates instantly, so you can experiment with different hole sizes before finalizing your material list.
Pro tips
- Add 5‑10 % extra bags to cover spillage and compaction.
- Round up the bag count; you can’t buy a fraction of a bag.
- Order bags in multiples of 5 to reduce shipping costs.
- Double‑check that the diameter is measured at the widest point of the hole.
Real-life examples
- A homeowner installing a fence wants to know how many concrete bags to secure each post.
- A small contractor building a deck needs material estimates for 12 post holes.
- A landscaper setting up a garden arbor must order the right amount of mix for multiple footings.
Case study
Mike was planning a 10‑post fence and kept guessing bag counts, ending up ordering 30 % too much. After using the calculator, he saw he needed only 22 bags, saved $45, and finished on schedule.