Home Improvement
Rails and concrete
Rails scale with sections while concrete scales with posts.
The Formula
rails = sections x rails per section, concrete bags = posts x bags per post
Rails scale with sections while concrete scales with posts.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| rails | Rail count | rails | Horizontal members needed. |
| sections | Sections | sections | One fewer than the number of posts. |
| r | Rails per section | rails | Two for short fences, three for six foot privacy. |
| b | Bags per post | bags | Usually two 60 pound bags per post. |
What Each Symbol Means
railsrails
Rail count
Horizontal members needed.
sectionssections
Sections
One fewer than the number of posts.
rrails
Rails per section
Two for short fences, three for six foot privacy.
bbags
Bags per post
Usually two 60 pound bags per post.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate fence posts page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Fence Posts, filed under Everyday Life. Every number the guide produces comes from substituting into this one line.