Shadowbox fence calculator
Calculate materials for a shadowbox fence, which alternates pickets on both sides of the rails for a semi-private, two-sided look.
Fence calculator
Enter your specs. Every result updates live and shows its formula.
Overview
Shadowbox fencing alternates pickets on opposite sides of the rails, so both sides of the fence show a similar finished look, and small gaps let some air and light through while still screening a direct sightline. Material quantities follow the same post and rail formulas as any other wood style here.
Picket count for shadowbox uses the same width-plus-gap formula as a classic picket fence, since shadowbox boards are typically spaced with a small gap on each side rather than butted tight.
Assumptions
- Shadowbox is a two-sided layout: pickets alternate on each face of the rails, so plan roughly twice the per-side board count for the full fence.
- The default picket gap is a small one, in keeping with the semi-private look.
- Posts and rails use the same formulas as the other wood styles.
Common mistakes
- Forgetting that shadowbox uses pickets on both sides of the rail, roughly doubling board count compared to a single-sided privacy fence of the same run, even though this calculator's picket-pitch formula is per side and needs adjusting for that if you are hand-checking a quote.
- Using a zero gap, which removes the alternating-slat look that defines this style.
- Ordering boards per side but only budgeting for one side when pricing the job.
Fence calculation formulas
The same math the calculator runs, in plain terms. Nothing here is a black box.
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Sections
sections = max(ceil(effective run / post spacing), 1)
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Post count
posts = (sections + 1) along the run, minus named corner and end posts already placed, plus 2 gate posts per gate
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Effective run
effective run = total length - sum of gate widths
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Rail count
total rails = sections x rails per section
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Picket count
pickets = ceil(run in inches / (picket width + gap)); total = ceil(raw x (1 + waste %))
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Board-on-board pitch
pitch = picket width - 1 in overlap
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Panel count
full panels = floor(run / panel width); add 1 cut panel if the remainder is over 0.01 ft; total = ceil(raw x (1 + waste %))
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Concrete volume
per-hole = pi x (diameter / 2)^2 x depth; total = per-hole x posts; bags = ceil(total / bag yield)
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Slope-adjusted run
slope run = effective run / cos(atan(slope % / 100)); shown alongside, counts use the flat run
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Cost
materials = (posts x post price + rails x rail price + infill x unit price + 60 lb bags x bag price) x regional multiplier; labor = effective run x labor per ft x terrain multiplier x regional multiplier; installed total = materials + gate hardware + removal + permit + labor
Every number the calculator shows comes from these formulas applied to your inputs.
Next step
Related calculators
- Wood fence calculator Calculate posts, rails, pickets and concrete for a pressure-treated pine, cedar or redwood fence. Every formula shown, cost optional.
- Board on board fence calculator Calculate pickets for a board-on-board fence, which overlaps boards for full privacy from both sides, with the overlap built into the formula.
- Privacy fence calculator Calculate posts, rails and pickets for a solid privacy fence in any material, with a zero-gap board layout by default.
Related reading
In-depth guides
Buying guide
Shadowbox fencing alternates pickets on opposite faces of the rail, so the fence reads as a similar finished surface from both yards rather than showing rails and fastener heads from one side, the way a single-sided privacy fence does. A small gap, commonly around half an inch to an inch, sits between the staggered boards, which lets some light and air through while still blocking a direct line of sight. It sits between privacy and board-on-board on the screening spectrum: more open than either, but still built for a semi-private boundary rather than an airy picket look.
Picket count on this page is computed per side using the same width-plus-gap pitch as a classic picket layout, since shadowbox boards are spaced rather than overlapped. Because shadowbox covers both faces of the rail, the actual board order for the full fence is roughly double the per-side count this calculator returns for one face, which is the single most common thing to miss when pricing this style against a one-sided fence. The standalone fence picket calculator is useful for re-running that per-side math against a different gap before doubling it.
Posts and rails are unaffected by the two-sided infill: spacing and rail count follow the same height-based rules as every other wood style on the wood fence calculator, 2 rails at 4 feet and under, 3 at 5 to 7 feet, 4 at 8 feet and taller, since the extra boards attach to the same rail run rather than adding structure. The fence rail calculator is the place to confirm rail count and total linear footage of rail stock separately from the picket decision.
For a side-by-side look at how shadowbox compares to board-on-board and a plain butted privacy layout, including when each one makes sense, board-on-board vs shadowbox vs solid privacy fence covers the tradeoffs in more depth than a materials calculator can. How many pickets for 100 feet of fence walks through the base picket pitch formula this page builds on, and the wood fence installation guide covers attaching alternating boards once the count is settled. The wood fence calculators hub lists every other style if shadowbox turns out not to be the final answer.
Shadowbox is primarily a wood construction technique, since the alternating slat layout is built board by board on site; vinyl and composite systems are generally sold as pre-assembled panels in a privacy style rather than as individual alternating slats, so a true shadowbox look is most practical in wood. If a vinyl or composite alternative is being priced for a similar semi-private look, it makes more sense to count pre-made panels than to translate this picket-pitch formula into those materials.
Because boards attach to both faces of the same rail run, rail spacing and fastening do more of the structural work on a shadowbox fence than on a single-sided style, even though the rail count itself follows the same height-based formula as any other wood fence. Checking that rails are sized and fastened to carry boards on both sides, rather than treating it as a single-sided attachment detail, is one of the judgment calls that falls outside what a material calculator can confirm on its own.
Because shadowbox is built board by board rather than as a pre-made panel, on-site layout accuracy matters more here than on a simpler privacy run: the alternating pattern only reads correctly if the gap and offset stay consistent from one picket to the next, so establishing the pitch once at the start of the run and holding it steady is more important than on a style where a slightly uneven gap is harder to notice. A story pole, a board marked with the picket and gap spacing, is a simple way installers keep that pattern consistent across a long run without remeasuring at every post.
Maintenance also looks a little different on a two-sided fence: both faces age and weather at a similar rate since both see roughly equal sun and moisture exposure, unlike a one-sided privacy fence where the show face often weathers differently from the structural face. That even exposure is one of the practical advantages of the style beyond its semi-private look, and it is worth factoring into a maintenance and staining schedule covering both sides equally rather than treating one face as the primary one.
Shadowbox also tends to suit properties where neighbors on both sides care about the finished look, since it is one of the few wood styles that gives both yards a comparable face rather than one side getting the structural rail view. That shared-appearance quality is sometimes the deciding factor over a plain privacy fence even when the privacy fence would be the lower-cost option, independent of the screening difference between the two styles.
Shadowbox also reads well on fences that run along a shared side yard, where a privacy fence's single finished face would otherwise leave one neighbor looking at exposed rails, since the alternating layout avoids that imbalance without requiring a conversation about which side gets the better-looking face.
Frequently asked questions
What is different about a shadowbox fence compared to privacy?
Shadowbox alternates pickets on both faces of the rail rather than all on one side, so it looks similar from both yards and lets in some light and airflow, while a privacy fence butts boards tight on one side only.
How many boards does a shadowbox fence need?
Roughly twice the count of a single-sided fence over the same run, because each face is covered. Use the picket calculator per side, then double the boards for the full fence.
What gap is typical for shadowbox spacing?
A smaller gap than a classic picket fence, commonly around 0.5 to 1 inch, keeps the semi-private look without closing the fence completely. The exact gap is a design choice and changes the per-side count.
Is shadowbox more expensive than a privacy fence?
Generally yes on materials, because a two-sided layout uses more boards over the same run. Posts and rails cost the same; the difference is in the infill boards.
Does shadowbox provide full privacy?
No, it screens a direct sightline but lets in light and air through the staggered gaps. If total visual privacy from every angle is the goal, a board-on-board or butted privacy layout blocks more.
Can shadowbox be built in vinyl or composite?
Vinyl panel systems are usually sold as pre-assembled privacy panels rather than alternating slats, so the true asset-for-asset shadowbox look is most practical in wood. If a vinyl or composite alternative is chosen, count panels rather than boards.
Do I need more posts for a shadowbox fence?
No. Posts and rails follow the same spacing rules as other wood styles. The extra boards sit on the same rails, so post count is unaffected.
Which rail count fits shadowbox best?
The same height-based suggestion as other wooden styles: 2 rails at 4 feet and under, 3 for 5 to 7 feet, 4 at 8 feet and taller. Shadowbox boards are attached to the rails on both sides, so rail spacing does the holding.