Article — Wood Fence Calculator
Wood fence calculator: sections, posts, rails, and pickets
A wood fence calculator estimates how many posts, rails, pickets, and bags of concrete you need for a fence of a given length, height, and post spacing. For a typical 100 ft, 6 ft tall privacy fence with 8 ft post spacing and 5.5 in pickets butted tight, you need 13-14 posts, 36-39 rails, and about 220 pickets, plus 14 bags of 60-lb concrete.
The material list drives the project budget, the truck load to the job site, and the time it takes to build. Sizing a fence correctly before buying lumber saves multiple trips to the supply yard and helps you negotiate a single bulk delivery. The calculator handles every typical residential layout, including gates and varying post spacing.
What a wood fence calculator estimates
Inputs are fence length (ft), height (ft), post spacing (ft), picket width (in), picket gap (in), number of gates, and optional price per picket. The calculator returns the section count, post count (including extra posts for gates), rail count (2 or 3 per section based on height), picket count, lumber linear feet for posts/rails/pickets, concrete volume and bag count, and an optional total picket cost.
The standard assumptions: 4-ft wide gates, 0.5 cu ft of concrete per post hole, an extra post per gate, 6-in extra picket length above ground for clearance, and 2.5 ft of post buried below grade. Tweak these in your local code zone if your frost depth, gate width, or fence style differs.
The "split-rail" fence — the classic American zigzag of overlapping wood rails without posts — predates nailed fencing by over a century. Settlers used it because it required no metal hardware and could be assembled with an axe alone. A modern picket fence has more parts (posts, rails, pickets, hardware, concrete) but is far stronger.
Anatomy of a wood fence
A standard residential wood fence has four major components: posts (the vertical supports buried in concrete), rails (the horizontal members spanning between posts), pickets (the vertical face boards attached to the rails), and hardware (fasteners, hinges, latches). Concrete anchors the posts. Gates are panels with hinges and a latch, sharing posts with adjacent fence sections.
Heights run 3 to 8 feet. The 6-ft height is the residential privacy standard. Pool codes often mandate 4-5 ft with no climbing footholds. Front yard fences are often 3-4 ft for visibility. Beyond 8 ft, most jurisdictions require permits and engineering review for wind-load resistance.
Posts: 13-14 (8-ft spacing, 1 gate)Rails: 24-36 (height-dependent)Pickets: ~220 (5.5 in, tight)Concrete: ~14 × 60-lb bagsHardware: ~$50-100Wood fence post spacing and depth
Post spacing of 6-8 feet is standard. Closer spacing (4-6 ft) gives a sturdier fence but uses more posts and concrete. Wider spacing (8 ft) saves cost but requires heavier rails (2×6 instead of 2×4) and often a middle rail. Beyond 8 ft is impractical for residential framing without bracing.
Post depth follows a simple rule: one-third of the fence height plus 6 inches, with a 24-in minimum. For a 6-ft fence, that is 30 in below grade. In cold climates, set posts at or below the frost line — Minnesota or Maine frost depths can reach 48 in. Frost heave is the most common cause of fence post failure in northern US states.
Picket width, gap, and layout
Common picket widths: 3.5 in (1×4 actual), 5.5 in (1×6 actual), 7.25 in (1×8 actual). For privacy, set the gap to 0 in and butt the pickets tight. For a semi-open look, 1-2 in gaps work well. For a picket-style decorative fence, 2-4 in gaps maintain transparency while keeping pets contained.
Picket count per section = ceiling((spacing × 12) / (picket_width + gap)). For 8 ft spacing, 5.5 in pickets, 0 in gap: (96 / 5.5) = 17.5, rounded up to 18 pickets per section. Plan to order 5-10% extra for cutoffs, knot-hiding, and rejects.
- Standard fence height = 6 ft (privacy)
- Post spacing = 6-8 ft (8 ft most common)
- Post depth = 1/3 height + 6 in, min 24 in
- Rails: 2 sections under 6 ft, 3 for ≥6 ft
- 1×6 picket actual width = 5.5 in
- 1×4 picket actual width = 3.5 in
- Concrete per post = ~0.5 cu ft (1 × 60-lb bag)
Wood fence material types and lifespan
Three common wood choices dominate residential fencing. Pressure-treated southern pine ($0.85-1.20 per board foot, lifespan 15-25 years with maintenance) is the budget standard. Western Red Cedar ($2-3.50 per board foot, lifespan 15-25 years without treatment) costs more but resists rot and insects naturally. Redwood ($2.50-4 per board foot, lifespan 20-25+ years) is the premium option but is regionally limited to the western US.
Composite fencing ($3.50-6 per board foot) and vinyl-clad alternatives last 25-30+ years but cost 2-3x more upfront. For a 100-ft fence, the lifecycle cost (material + replacement) often favours cedar over pressure-treated, even though the initial spend is higher.
Wood fence cost per linear foot
For a 6-ft tall, 8-ft post spaced privacy fence, expect $15-25 per linear foot in pressure-treated materials only, or $30-40 in cedar. Add roughly $30-50 per linear foot for professional installation labour. Total installed costs land at $45-90 per linear foot.
A 100-ft pressure-treated privacy fence costs about $1,500-2,500 in materials, or $4,000-7,500 installed. The same fence in cedar runs $3,000-4,000 materials, $7,500-12,000 installed. Gates, hardware, and post caps typically add $50-150 per gate.
For a DIY build, save by buying lumber from a builder's supply (not a big-box store) and renting a one-man post hole auger for the day. The auger digs in 30-60 seconds per hole versus 5-15 minutes by hand, turning a 14-post project from a full weekend into an afternoon.
Common wood-fence mistakes
Three errors recur. First, undersized post holes. A 6-ft fence needs at least 30-in deep posts in concrete, not 18 or 24. Shallow posts heave with frost and lean within a couple of years. Second, forgetting gate posts. Gates need double posts (one each side) and heavier hinges than fence sections. Add 2 extra posts and an extra rail for each gate. Third, picket spacing miscounts. The 5.5-in figure is the actual planed width of a "1×6" picket, not the nominal 6 inches. Using 6 in in the calculator underestimates picket count by about 9%.
Most US jurisdictions limit fence height to 6 ft in side and rear yards, 4 ft in front yards, and require permits above those heights. Pool codes often mandate 5 ft minimum, climbing-resistant. Property-line setbacks vary. Always check with your local building department before construction to avoid mandatory removal or fines.