Preset dimensions
Common project sizes
What this fence post concrete calculator calculates
A nominal 4 × 4 post is 3.5 × 3.5 in actual. Subtracting that displacement matters when a 12 in × 36 in hole is filled around the post.
Formula
Hole cylinder volume − actual post volume = concrete volume; multiply by post count and add waste before converting to bags.
Worked example
A 12 in × 36 in hole is 2.356 ft³. A 5.5 in actual 6 × 6 post displaces 0.630 ft³, leaving 1.726 ft³, which rounds to 3 80 lb bags without waste.
Ordering decision
Set post depth and hole diameter from the fence plan. Local frost depth, wind exposure, and soil conditions govern the final hole.
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 concrete for each fence post 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.
Concrete for each fence post
This construction fence-post calculator estimates the concrete around one or more posts and subtracts the space occupied by the actual post. It is deliberately about post holes, not a general slab or aquarium calculation.
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.