How Much Concrete Does Each Fence Post Need?
Estimate concrete from the hole size, the actual post size, and the bag yield printed on the product—not a generic “bags per post” rule.
By Fence Planner · 1 min read · Updated 2026-07-19
The short answer
Start with the hole size your local requirements and fence system call for, then let the planner estimate the concrete for all matching posts together.
Why it matters
A deeper or wider hole uses much more concrete. Gate and corner posts may need a different detail from ordinary line posts, and bag yields vary by product.
Do this first
- Separate the posts that will use different hole sizes or footing details.
- Measure the actual post cross-section or use the manufacturer’s listed size.
- Enter the chosen hole diameter, depth, and the concrete yield printed on the bag.
- Add a modest contingency if your holes are likely to vary, then round the project total up to whole bags.
Use Fence Planner for this part
It gives a transparent starting total for a cylindrical hole. It rounds the entire group rather than needlessly rounding every post into extra bags.
How the estimate works
The calculator starts with a round hole volume, subtracts the part of the post that sits in the hole, multiplies by how many posts share that hole size, then divides by the bag yield printed on the product. Whole bags are rounded once for the whole group.
Open this concrete bag-yield exampleYou will be asked to confirm before anything replaces your current plan.
Educational planning content only. Not a substitute for local codes, surveys, engineering, or professional advice. See Methodology for how this guide was prepared and how the calculator works.