A wood fence is really four shopping lists: posts, rails, pickets and the concrete that holds the posts up. Get those four numbers and you can price the whole job. Here is how each one is worked out.
Posts
Count the sections first. Divide your run length by the post spacing, 8 ft is the usual choice, and round up. A 100 ft run at 8 ft spacing is 13 sections. Posts are always one more than sections, so that is 14. Every gate needs its own post on the latch side, so add one per gate.
Closer posts cost more but stiffen the fence and suit windy spots or heavier panels. Going past 8 ft tends to let the rails sag over time.
Rails
Rails are the horizontal backbone the pickets nail to. Height decides how many you run per section:
| Fence height | Rails per section |
|---|---|
| Up to 4 ft | 2 |
| 6 ft | 3 |
| 8 ft and over | 4 |
Multiply that by the number of sections. A 6 ft, 13-section fence needs 39 rails.
Pickets
Take the fenced length in inches and divide by one picket width plus one gap. A privacy fence butts the boards almost tight, so the gap is close to zero; a spaced picket fence leaves an inch or two. For 100 ft of 5.5 in boards with a quarter-inch gap, that is 1,200 ÷ 5.75, which rounds up to 209 pickets. Subtract the width of any gates from the run before you count, since you do not clad the opening.
Concrete
Each post sits in a hole roughly three times its width and about a third of the fence height deep, never shallower than the frost line. A 4×4 in a 12 in hole dug 2 ft down takes a bit over a cubic foot of concrete, which is about three 80 lb bags. Multiply by your post count and round up, a part-used last bag is normal.
Skip the arithmetic
The wood fence calculator does all of this as you type. Enter the length, height, spacing and picket size, add any gates, and it returns the full list. Or sketch the run in the fence drawing tool and read the materials straight off the drawing.