The short answer: divide your run length by the post spacing, round up, and add one. At the common 8 ft spacing, a 100 ft fence needs 14 posts. Then add a post for every gate and every corner.
The formula
posts = (run length ÷ post spacing, rounded up) + 1
The “+1” is the closing post, a run of three sections has four posts, like fence rails with bookends. Then add one post on the latch side of each gate, and one at each corner where the line changes direction.
Common lengths at 8 ft spacing
| Run length | Sections | Posts |
|---|---|---|
| 25 ft | 4 | 5 |
| 50 ft | 7 | 8 |
| 100 ft | 13 | 14 |
| 150 ft | 19 | 20 |
| 200 ft | 25 | 26 |
Chain link can use 10 ft spacing, which lowers these counts; tighter spacing in windy areas raises them.
The extras people forget
- Corners: one post each, on top of the straight-run count.
- Gates: a post on the latch side of every gate.
- Slopes: a step-down in the fence line may need an extra post.
Count it for your fence
Enter your run and spacing in the fence post spacing calculator for the exact count and even spacing, or draw the layout in the fence drawing tool and it places every post, corners and gates included.