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 yards, bags, and cubic feet.
This tool takes the diameter, depth, and quantity of your post holes and instantly converts them to three practical units: total cubic feet, cubic yards, and the number of 80‑lb concrete bags needed. Knowing the cubic‑yard volume helps you compare against delivery truck sizes, while the bag count tells you exactly how many mixes to order. The calculator uses the standard that one 80‑lb bag yields about 0.6 cubic feet, then divides the total cubic‑foot volume by that figure and rounds up to the nearest whole bag. Read the results: cubic feet gives raw volume, cubic yards is volume ÷ 27, and bags is the rounded‑up division result. No guesswork, just clear numbers for budgeting and ordering.
Pro tips
- Add about 10% extra for spillage and settling.
- Round the bag count up to the next whole bag.
- Order bags in multiples of 5 for bulk discounts.
- Double‑check diameter and depth; small errors multiply volume.
Real-life examples
- Planning concrete for a new garden fence’s post holes.
- Estimating material for deck support posts.
- Ordering concrete for a mailbox post installation.
Case study
Sam needed 12 fence posts 4 in diameter, 3 ft deep. The calculator showed 0.75 cubic yards, 4 bags of 80‑lb mix. He ordered exactly 4 bags, saved $30, and finished on schedule.