Work out the material take-off for a fence run: number of posts, boards or panels, rail length and the concrete for the post holes. Add your own unit prices for a cost estimate.
| Input | Result |
|---|---|
| 100 ft run · 8 ft spacing · 6 ft tall · 6 in boards (sample rates) | 14 posts @ 7.69 ft · 200 boards · 200 ft rail · 0.36 yd³ · $5006.3 |
| 150 ft run · 8 ft spacing · 6 ft tall · 6 in boards (sample rates) | 20 posts @ 7.89 ft · 300 boards · 300 ft rail · 0.65 yd³ · $7506.96 |
| 60 ft run · 6 ft spacing · 4 ft tall · 6 in boards (sample rates) | 11 posts @ 6.00 ft · 120 boards · 120 ft rail · 0.28 yd³ · $1647.66 |
A fence material list is three independent counts, and mixing them up is the usual reason a take-off comes up short. Posts follow the spacing and the run length. Boards or panels follow the run length and the board width. Rails follow the run length and how many rows you run between posts. Only the posts get the +1, because only the posts have to appear at both ends.
The part that is not arithmetic is the hole depth. Posts set above the frost line heave out of plumb in freezing weather, and how deep the frost line is changes completely from one region to another. This is why the depth field has no default value you should trust blindly, look up the footing depth your building department specifies.
Concrete for the holes is quoted separately from the lumber, usually in cubic yards for a long run or in bags for a short one. This page totals the cylinder volumes so the number you take to the supplier is the number your holes actually need.
Because dividing the run by the spacing counts the gaps between posts, not the posts themselves, there is a post at each end as well as between the gaps. A 100 ft run at 8 ft spacing is 12.5, which rounds up to 13 gaps and therefore 14 posts. The page also shows the spacing that results, 7.69 ft, so you can space the posts evenly along the run instead of ending with one short section.
Six to eight feet on centre is the usual range for wood fences; chain link commonly uses ten. The right answer depends on your fence style, panel size, wind exposure and local code, so follow your material supplier's specification or your plans rather than a default.
Deep enough to reach below your local frost line, since posts in shallow holes heave in freezing ground. Frost depth varies enormously by region, so check the footing depth your building department requires, that figure, not a generic one-third-of-height rule, is what governs.
Divide the run in inches by the board width. A 100 ft run with 6 in boards is 1,200 ÷ 6 = 200 boards. The height sets how long each board is, not how many you need, because boards run vertically. Buy about ten percent extra for defects and cuts.
Each hole is a cylinder: π × radius² × depth. This page totals them and converts to cubic yards, which is how concrete is sold. Twenty-four to thirty bags of 50 lb mix is a rough sense of scale for a typical run, but let the calculator work it from your own hole size and count.