Fence picket calculator
The picket count is set by one number most people guess: the gap. Change 1/4 inch to 3/4 inch on a 100 ft run and you need 18 fewer pickets. The post count is set by spacing, and posts cost more than pickets.
Fence run
How this is calculated
- Pickets = ⌈(run × 12) ÷ (picket width + gap)⌉. Rounded up, because a partial picket is a picket.
- Bays = ⌈run ÷ post spacing⌉.
- Posts = bays + 1. Two end posts, one between every pair of bays.
- Rails = bays × rails per bay, in linear feet.
The check row exists because the rounding is not obvious: the calculator picks the smallest whole number of pickets that covers the run, so the pickets plus gaps usually come out slightly longer than the run itself. That overage is the fence's slack, and it is better to know it than to discover it at the last bay.
Worked example
A 100 ft privacy run, 5.5″ pickets at a 1/4″ gap, posts every 8 ft, two rails:
- Run in inches = 1,200″
- Pickets = ⌈1,200 ÷ 5.75⌉ = ⌈208.7⌉ = 209 pickets
- Bays = ⌈100 ÷ 8⌉ = 13
- Posts = 13 + 1 = 14 posts
- Rails = 13 × 2 × 8 = 208 linear ft
Add 5–10% pickets for breakage and end cuts. On 209 pickets that is 10 to 20 spares, and they are the same board you will need in three years when one splits.
Gap by fence type
| Fence | Gap | Pickets per 100 ft |
|---|---|---|
| Privacy, dog-eared | 0″ | 219 |
| Privacy with shrinkage allowance | 1/4″ | 209 |
| Picket, classic | 2″ | 160 |
| Picket, open | 3″ | 141 |
| Pool barrier | under 4″ | Set by the local code, not by taste |
Zero gap looks tight and becomes a problem: wet pickets swell and the run buckles. A quarter inch is the usual compromise — it reads as solid, and it leaves room for movement. It also costs you 10 pickets per 100 ft compared with butting them tight.
What the picket count leaves out
- It does not design the post foundation. Post diameter, hole depth and frost depth are set by your local code and by the wind load on the fence, not by spacing alone.
- It does not handle corners, gates or grade changes. A gate needs its own posts rated for the leaf weight, and a corner post carries load from two directions. Add those by hand.
- It counts one run. For an L-shaped or stepped fence, run each straight section separately and add the counts.
- It does not include concrete, hinges or fasteners. Those are on the fence post calculator and the hardware aisle.
Questions people actually ask
Questions people actually ask
How many pickets do I need for 100 feet of fence?
At 5.5″ pickets with a 1/4″ gap, 209. Butted tight it is 219, and at a 2″ gap it is 160. The gap is the whole answer, which is why guessing at it goes wrong.
How far apart should fence posts be?
Eight feet for most picket and privacy fences, six feet on a tall privacy fence in wind, and never more than the rail span your rail size can carry. Spacing drives post count, and posts are the expensive part.
Should I leave a gap between pickets?
Yes, a quarter inch. Butted pickets swell when wet and push the run out of line. The exception is a fence specified tight by an engineer for a specific reason.
How many rails does a privacy fence need?
Two for a 4 ft fence, three for 6 ft. The top rail carries the pickets, the bottom rail stops them cupping, and a mid rail on a tall fence stops the run from bowing between posts.