Construction

Instant, private, and free

Post-Hole Concrete Calculator.

Calculate concrete volume for cylindrical post holes without assuming bag yield.

On-device calculationNo signup
01

Set your values

Results update as you type.

Radius: 0.5

Radius

0.0000
Per-hole volume: 2.3562

Per-hole volume

0.0000
Base volume: 9.4248

Base volume

0.0000
Volume: 10.3673

Volume

0.0000
holeCount: 4

holeCount

0.0000
wastePercent: 10

wastePercent

0.0000

Results use only the stated formula and entered dimensions; no material density, pricing, code, or structural recommendation is inferred.

Use Cases

Fence Post Installation

Determine the exact concrete volume needed for multiple fence posts to avoid over- or under-ordering.

Example: For 10 holes, 12 inches diameter, 36 inches deep, with 10% waste, the calculator gives total cubic feet.

Deck or Pergola Support Posts

Plan concrete requirements for structural posts, ensuring you have enough mix for all footings.

Example: Calculate for 4 holes, 18 inches diameter, 48 inches deep, with 5% waste.

Frequently Asked Questions

How does the Post-Hole Concrete Calculator work?
It calculates the volume of each cylindrical hole using the formula for cylinder volume (πr²h), multiplies by the number of holes, and adds the waste percentage you specify. The result is the total concrete volume needed in cubic units.
What units should I use for hole diameter and depth?
Use the same units for both diameter and depth (e.g., feet, inches, meters). The calculator will output the volume in cubic units of that same unit (e.g., cubic feet, cubic inches, cubic meters).
Why is a waste percentage included?
Waste accounts for spillage, over-excavation, or uneven holes. Adding a waste percentage (e.g., 10%) ensures you order enough concrete to avoid running short.

Tips & Common Mistakes

Tips

  • Measure hole diameter at the widest point, as holes are often slightly larger than the post.
  • Use the same unit for diameter and depth to get accurate cubic volume.
  • Add a waste percentage of 5-10% to account for spillage and irregular holes.
  • For multiple holes, enter the total count to get the combined volume.

Common Mistakes to Avoid

  • Using different units for diameter and depth (e.g., inches for diameter, feet for depth) without converting.
  • Forgetting to include the waste percentage, leading to a shortage of concrete.
  • Assuming the hole is perfectly cylindrical when it may be wider at the top, so measure carefully.

Last updated: August 13, 2026