How Many Fence Posts Do I Need?
By the TapeMeasureCalc team · Updated · 8 min read
Counting fence posts sounds like simple division, and for one straight run it nearly is. The mistakes creep in at the ends, the corners and the gates. This guide walks through each of those, then counts a real L-shaped garden fence from start to finish: posts, rails, pickets and the concrete to set them.
One straight run
Divide the length of the run by your post spacing, round up, then add one post for the far end.
Posts = ⌈Run length ÷ Spacing⌉ + 1
A 50 ft run with posts every 8 ft: 50 ÷ 8 = 6.25, which rounds up to 7 sections, so 8 posts. The “+1” is the one people forget. Seven sections need eight posts, the same way seven gaps in a row of fence boards need eight boards.
Spacing of 6 to 8 ft (about 1.8 to 2.4 m) is common for wood fences. Tall, solid fences on windy sites often need closer posts, and panel fences use whatever width the panels are.
Even out the sections
In the 50 ft example, seven 8 ft sections would add up to 56 ft, so the last bay comes out short. Most builders spread the difference instead: 50 ÷ 7 = 7 ft 1¾ in between post centres. The post count stays the same and the fence looks deliberate rather than squeezed at one end.
Corners and gates
Corners. Count each straight side as its own run, then take one post off for each corner, because two runs share it.
Gates. Take the gate width out of the run, count posts for what’s left, and add one more post per gate. A gate in the middle of a run splits it in two, so it needs a post on each side of the opening. Gate posts carry more load than line posts, and many people use a heavier post there.
Worked example: an L-shaped garden fence
A back fence of 60 ft and a side fence of 40 ft meet at a corner. The side fence has a 4 ft gate. Posts go every 8 ft, with three rails per section and 5½-inch pickets butted tight for privacy.
Back run, 60 ft: 60 ÷ 8 = 7.5, so 8 sections and 9 posts.
Side run, 40 ft with a gate: 40 − 4 = 36 ft of fence. 36 ÷ 8 = 4.5, so 5 sections. That’s 5 + 1 + 1 (gate) = 7 posts, but the corner post is already counted in the back run, so add 6.
Posts in total: 15.
- Rails: 13 sections × 3 = 39 rails
- Pickets, back: 720 in ÷ 5.5 = 130.9, so 131
- Pickets, side: 36 ft is 432 in. 432 ÷ 5.5 = 78.5, so 79
- Pickets in total: 210, plus a few spares for split or warped boards
In metric: an 18 m back run and a 12 m side run with a 1 m gate, posts every 2.4 m, also comes to 15 posts (9 on the back, 6 more on the side).
How long should the posts be?
A post is the fence height plus the part in the ground. How deep to bury it depends on your soil, frost depth, wind exposure and local rules, so check before you buy. As an example of the arithmetic: a 6 ft fence with 2 ft of post in the ground needs 8 ft posts, which is a standard length.
The 8 ft lengths also suit 8 ft spacing nicely. Each rail spans one section, so 8 ft rail boards drop straight in.
Concrete for the posts
If you set posts in concrete, the bags of concrete guide works through a typical hole: 10 inches across with 26 inches of concrete around a 4×4 needs about 1 ft³. For 15 posts that’s 15 ft³, or 25 bags of 80 lb at a 0.6 ft³ yield. Buy one or two extra.
Before you dig
- Confirm where your boundary actually is. A surveyed line beats an old fence.
- Call your local utility locating service before digging any post holes.
- Check height limits, setbacks and whether a permit or your neighbour’s agreement is needed.
- Run a string line between the end posts so every hole lands in a straight line.
Do it with the calculators
The fence calculator counts posts, rails and pickets for one straight run with gates. For an L or U shape, run it once per side and subtract the shared corner posts. Then use the concrete bag calculator for setting them, and the paint calculator if you’re staining or painting the boards.