A fence looks simple until you start counting parts: posts at the right spacing, rails between them, pickets across the face, and concrete to set it all. Miss one and the project stops. This calculator turns a single measurement — the total run — into the full parts list, with sensible defaults you can adjust for your style of fence.
How fence materials are calculated
Posts = sections + 1
Rails = sections × rails per section
Pickets = (length × 12) ÷ (picket width + gap)
Everything flows from the post spacing. Each gap between two posts is a section, and the parts count builds from there. The final +1 on the posts is the one people forget — a run always needs one more post than it has sections.
Measuring and planning the run
- Walk the line and measure the total length, then mark corners and gate openings, which each need their own posts.
- Choose post spacing for your conditions: 8 ft is economical, 6 ft is stronger for tall privacy fences or exposed, windy sites.
- Decide the picket gap: zero for a solid privacy fence, or a deliberate gap (often equal to a picket width) for a classic spaced picket look.
Choosing rails and posts
| Fence height | Rails per section |
|---|---|
| Under 4 ft | 2 rails |
| 4–6 ft | 2–3 rails |
| 6 ft privacy | 3 rails |
Posts should be rated for ground contact and set deep enough to resist frost heave and wind. A common rule is to bury one-third of the post height, so a 6 ft-tall fence uses 8 ft posts set about 2 ft deep.
A worked example
A 100 ft privacy fence, posts every 8 ft, three rails, 5.5 in pickets butted with no gap:
- Sections = 100 ÷ 8 = 12.5 → 13 sections
- Posts = 13 + 1 = 14 posts (plus extras for corners and gates)
- Rails = 13 × 3 = 39 rails
- Pickets = (100 × 12) ÷ 5.5 = about 218 pickets
- Concrete ≈ 14 posts × 1.5 = 21 bags
Setting posts in concrete
Post stability makes or breaks a fence. Dig holes about three times the post width and one-third the post height, add a few inches of gravel for drainage, then set the post plumb in concrete. Fast-setting post concrete can be poured dry into the hole and wetted, which speeds the job. Let posts cure before hanging rails and pickets. The related concrete calculator can size the bags precisely from your hole dimensions.
Finishing and longevity
Whatever the material, a wood fence lasts far longer sealed or stained, and the best time is after the timber has dried but before it weathers. The related deck stain calculator works for fences too — it estimates coverage from the total surface area. Plan to reseal every couple of years, and inspect posts at ground level annually, since that is where rot begins.
Setting posts that outlast the fence
Posts are where fences fail first, so they reward extra care. Dig holes about three times the post width and at least one-third of the post height deep, going below the frost line in cold climates so heaving does not lift them. A few inches of gravel at the bottom lets water drain away from the end grain. Set the post plumb and brace it before pouring concrete, then crown the concrete slightly above grade so water sheds away rather than pooling at the post. Corner and gate posts take the most stress and benefit from deeper, wider footings — the related concrete calculator sizes the mix precisely.
Gates and corners need extra material
The base calculation covers a straight run, but real fences have corners, ends and gates that each demand more. Every corner is an additional post where two runs meet. A gate needs a sturdy, often oversized post on the hinge side to carry its swinging weight without sagging, plus gate hardware. Slope adds complexity too: on a hillside you either step the fence down in level sections (more posts) or rack the panels to follow the grade. Walk and sketch the whole boundary, marking corners, gates and slope changes, and add posts and hardware for each before ordering.
Privacy, picket and other styles
Fence style drives the picket and rail counts. A solid privacy fence butts pickets edge to edge with no gap, using the most material and needing three rails for height and rigidity. A traditional picket fence spaces the boards, often a picket-width apart, halving the picket count for the same run. Post-and-rail and ranch styles use few or no pickets at all. Shadowbox fences alternate pickets on each side of the rails for a fence that looks finished from both sides and lets air through. Set the picket width and gap in the calculator to match your chosen style for an accurate count.
Materials and maintenance
Pressure-treated pine is the economical default and accepts stain well. Cedar resists rot and weathers to an attractive grey if left unsealed, or holds its colour with regular staining. Vinyl and composite fencing cost more up front but shrug off rot and need only occasional washing. Metal posts in concrete with wood rails and pickets combine longevity with a traditional look. Whatever the material, sealing or staining a wood fence after the timber dries, and inspecting posts at ground level each year where rot begins, are what keep a fence standing and looking good well beyond its first few seasons.
Estimating cost and labour
Fence cost is driven by material, height and length, plus the concrete and hardware that the headline picket price ignores. Pressure-treated pine is the economical choice; cedar costs more but lasts and looks better; vinyl and composite cost most up front but shrug off rot. To the pickets, rails and posts add concrete (one to two bags per post), gate hardware, fasteners and any post caps. Labour is significant if you hire out, since digging and setting posts is the slow part — expect installation to rival material cost. Setting posts and waiting for concrete to cure is also what makes a fence a multi-day DIY job rather than a single afternoon. The calculator's post, rail and picket counts let you price the material accurately and compare contractor quotes; remember to add the corner and gate posts the base run does not include, and a little extra picket stock for the inevitable warped or split board.
Frequently asked questions
How many fence posts do I need?
Divide the total length by the post spacing, then add one for the final post. A 100 ft fence with posts every 8 ft needs 13 sections and 14 posts. Corners and gates need extra posts.
How far apart should fence posts be?
Most wood fences use 6 to 8 feet between posts. Closer spacing makes a stronger fence in windy areas or for heavy privacy panels; 8 ft is the common maximum.
How much concrete per fence post?
Plan for about 1 to 2 bags of 50 lb concrete per post, depending on post and hole size. A hole one-third the post height and three times its width is a good rule for stability.
How many pickets do I need for a privacy fence?
For a solid privacy fence with no gaps, divide the fence length in inches by the picket width. A 100 ft fence with 5.5 in pickets needs about 218 pickets; add a gap for a spaced picket look.