What this post hole concrete calculator calculates
The hole is a cylinder, but the concrete is not the full cylinder when a post occupies the center. A 12 in × 36 in hole contains 2.356 ft³ before the post is subtracted.
Formula
π × radius² × depth − post width² × depth = net concrete volume.
Worked example
With a 5.5 in actual post in that 12 in × 36 in hole, the net is 1.726 ft³ before waste, or 3 80 lb bags at a 0.60 ft³ yield.
Ordering decision
Use a separate gravel quantity for the base. Do not count the post twice or use a nominal post size as its displacement.
The page cites the applicable Uzi Tools reference table beside the calculator. Product labels, current editions, local code, and a licensed professional govern structural, electrical, and life-safety work.
How to use it
- Enter the measured dimensions and keep the displayed units beside each field.
- Review the round fence post-hole volume result and the substituted formula before ordering.
- Adjust waste for the layout, cut pattern, product package, and site conditions.
- Copy or print the material list, then verify the cited product data and local requirements.
Round fence post-hole volume
Use this fence post hole calculator for round holes with a gravel base and an optional post inside. The result separates hole volume, post displacement, and concrete so the order is easy to check.
Limits and professional review
Measurements, product yield, waste, moisture, and site conditions can change the order quantity. Local code and a licensed professional govern structural and electrical work.