How many fence posts do I need?
For one straight run, divide the length by the most you want between posts, round up to get the sections, and add one. A post stands at each end of every section, and neighbouring sections share one.
| Straight fence | Posts 6 ft apart at most | 8 ft at most | 10 ft at most |
|---|---|---|---|
| 50 ft | 10 (5 ft 6 3/4 in apart) | 8 (7 ft 1 3/4 in apart) | 6 (10 ft apart) |
| 100 ft | 18 (5 ft 10 1/2 in apart) | 14 (7 ft 8 1/4 in apart) | 11 (10 ft apart) |
| 150 ft | 26 (6 ft apart) | 20 (7 ft 10 3/4 in apart) | 16 (10 ft apart) |
| 200 ft | 35 (5 ft 10 1/2 in apart) | 26 (8 ft apart) | 21 (10 ft apart) |
| 300 ft | 51 (6 ft apart) | 39 (7 ft 10 3/4 in apart) | 31 (10 ft apart) |
Every corner, end and gate changes the count, which is why the calculator takes the fence one side at a time. A corner post is shared by two sides. A gate takes a post on each edge, and the opening itself needs none.
Spacing posts evenly
The usual way to lay out a fence is to set posts 8 feet apart from one end and cut whatever is left into a short last section. It works, but it looks like an afterthought.
The calculator spreads each side evenly instead. A 70-foot side with posts no more than 8 feet apart becomes 9 equal sections of 7 ft 9 1/4 in, rather than 8 at 8 feet and one of 6 ft. Same number of posts, and a fence that looks planned. Mark the spacing with a string line before you dig.
Vinyl and aluminum are different. Their panels come in a fixed width, so the posts have to be that far apart, and the last panel on each side is cut down to fit. The calculator counts those cut panels for you.
Corner, end and gate posts
The posts at the ends of a fence take more strain than the ones in the middle, and the gate posts most of all. Chain link uses a heavier terminal post at every end, corner and gate, often 2⅜ inches across against 1⅞ for a line post, and the fabric is stretched between them with a tension bar at each end. The calculator counts those too.
On wood fences, many builders set the gate posts as 6×6s and deeper in the ground. Vinyl gate posts get a metal insert so they don't flex under a swinging gate. The suggested prices allow for both.
How long each post should be
The height of the fence plus the depth in the ground. A 6-foot fence with posts 2 feet down needs 8-foot posts, which is why that's the most common length on the rack. For the depth, the concrete maker's rule is a third to a half of the height above ground, deeper in cold places:
| Fence height | Post in the ground | Hole, with 6 in of gravel | Post length to buy |
|---|---|---|---|
| 4 ft | 16–24 in | 22–30 in | 8 ft |
| 5 ft | 20–30 in | 26–36 in | 8 ft |
| 6 ft | 24–36 in | 30–42 in | 8 ft or 10 ft |
| 8 ft | 32–48 in | 38–54 in | 12 ft |
Fair questions
How do I count a curved fence?
Enter the curve as several short sides. Posts spaced evenly along short straight stretches is how a curved fence is built anyway.
Should posts be closer in windy places?
Often, yes. A solid privacy fence catches the wind like a sail, and some builders set posts 6 feet apart for tall fences in exposed spots. Try 6 ft above and see what it does to the count.
How much concrete do the posts take?
The estimate counts 50 lb bags for holes about three times the width of the post. For your exact holes, follow the link under the estimate: it opens the post hole concrete calculator with your posts already filled in.
Sources
- Quikrete, Setting Posts in Concrete: hole width, hole depth and how much concrete a post takes.
- Call 811: the national call-before-you-dig service, for when and how to have buried utilities marked.
- How we calculate: every suggested price behind this calculator, with the date it was last reviewed.
