Fence Picket Calculator

Fence picket calculator for the picket count, equal gaps, marking positions, picket length and the dry-gap shrinkage on spaced, solid privacy, shadowbox or horizontal board fences.

How a Fence Picket Calculator Counts Pickets

The quick way to count fence pickets is to divide the fence length by one picket width plus one gap, using the same unit for both. A fence picket calculator then fits that count to the run so the first and last pickets land flush with the ends.

$$N=\frac{12L}{w+g}$$

L is the fence length in feet, w is the actual picket width in inches and g is the gap. For 100 ft of 3-1/2 in pickets with a 2 in gap, 1,200 in ÷ 5.5 in = 218.18, which rounds up to 219 pickets.

$$N=\lceil \frac{12L-w}{w+g}\rceil +1$$

The flush-end version counts the first picket, then how many picket-plus-gap steps fit in the rest. A fixed 2 in gap would leave the last picket hanging 2-1/2 in past the end, so the gaps are evened out to 1.989 in and the run closes exactly.

With 10% waste for splits and culls, the fence picket calculator orders 241 pickets for that 100 ft fence. The extra covers boards with large knots, warps and the odd miscut, which is why waste is figured on the count instead of on the length.

How Many Pickets for 100, 200 and 30 Feet of Fence

A 100 ft picket fence takes 219 pickets of 3-1/2 in width at a 2 in gap, and a 200 ft fence takes 437. The fence picket calculator runs every length on the same flush-end layout, so short runs come out slightly higher per foot.

Every fence picket calculator row here uses 3-1/2 in pickets, a 2 in target gap and a $2.25 starting price per picket, so enter your own price for a real total. Pickets per metre settle near 7.2 on long runs, and pickets per 8 ft land at 18 for one section.

Pickets are only part of a fence budget. The full cost of 200 ft of fence, with posts, rails, concrete and gates, comes from the Fence Calculator, and the Wood Fence Calculator adds wood-specific framing.

Standard Fence Picket Sizes

The standard fence picket is a 1×4 or 1×6 board, which measures 3-1/2 in or 5-1/2 in wide. Nominal sizes are larger than the actual width, so count with the measured face width or the fence picket calculator will come up short.

The fence picket calculator sets picket length as the fence height minus the gap you leave above the ground. Pickets shouldn't touch the soil, since end grain in damp ground rots first, so a 2 in clearance turns a 4 ft fence into 46 in pickets cut from 48 in stock.

A 6 ft fence with the same clearance needs 70 in pickets from 72 in stock. Common picket stock runs 36, 42, 48, 60, 72 and 96 in, and a fence picket length calculator should round up to the next length you can buy.

Fence Picket Spacing and Even Gaps

Picket spacing is the gap left between boards, and a fence picket calculator adjusts it slightly so no sliver or overhang is left at the end. Marking each picket's left edge from one end works better than measuring every gap, because small errors don't add up.

$$g=\frac{C-nw}{n+1}$$

For pickets fitted between posts, C is the clear opening, n is the picket count and w is the picket width, with one gap at each post as well as between boards. Face-mounted pickets that run over the posts use n - 1 gaps instead.

An 8 ft section with 4×4 posts leaves a 92-1/2 in clear opening. Asked to keep every gap at 2 in or less, the fence picket calculator fits 17 pickets with 1.833 in gaps, marked every 5-5/16 in on center, while 12 pickets in the same opening spread to 3-7/8 in gaps.

Cut one spacer block to the gap and use it for every board, checking the running count every few pickets. That is how to calculate a fence gap and install pickets with even spacing without measuring each one.

Wood Shrinkage and Picket Gaps

Wood pickets shrink across their width as they dry, so the gap you install grows. Shrinkage starts at about 30% moisture content and runs in a straight line down to dry wood, according to the Wood Handbook chapter on moisture relations.

$$\Delta w=w\times \frac{S_0}{100}\times \frac{30-M}{30}$$

Δw is the width lost, w is the picket width, S₀ is the tangential shrinkage from green to oven-dry in Wood Handbook Table 4-3, and M is the final moisture content. Moisture above 30% counts as 30%, since wood doesn't shrink until it drops below that point.

For treated southern pine, the fence picket calculator uses the average of loblolly, longleaf, shortleaf and slash pine in Table 4-3. Wet treated pine pickets installed at a 1.989 in gap open to about 2-1/8 in once dry, so set them at 1-13/16 in to finish near 2 in.

Solid privacy boards go up tight when wet. Each 5-1/2 in board loses about 1/4 in drying from 30% to 12%, so gaps that size open on their own, and a spacer at install would leave wider gaps later. Vinyl and composite pickets don't shrink.

Shadowbox and Horizontal Board Fences

A shadowbox fence puts boards on alternate sides of the rails, each lapping its neighbors. With 3-1/2 in boards and a 1 in lap, the front boards sit 3.48 in apart and 100 ft of fence takes 481 boards, more than double a spaced picket fence.

With 5-1/2 in boards on a 6 ft shadowbox, the same 100 ft takes 267 boards set 9 in apart on center on the front face. The lap shrinks from 1 in to about 3/4 in as treated pine dries.

For a horizontal fence, the fence picket calculator stacks boards from the ground up instead of side by side. A 6 ft fence with 5-1/2 in boards and 2 in ground clearance fits 12 rows in 70 in with 0.364 in gaps, and 100 ft needs 156 boards 8 ft long, 13 per row.

Horizontal boards shrink in height the same way pickets shrink in width, so a 0.364 in gap installed wet opens to about 0.61 in. Run each board post to post and stagger the joints from row to row where the posts allow.

Picket Fence on a Slope

A picket fence on sloped ground either racks with the grade or steps down in level sections. Racked pickets stay plumb and keep the same spacing on the level run, so the picket count doesn't change, but the rails run longer.

On a 20% slope, each 8 ft section's rails run 1.98% longer, or 8 ft 1-7/8 in, so they need 10 ft boards. At 10% the rails grow only 1/2 in per section, yet that still moves them past 8 ft stock.

Stepped sections keep level tops and leave the rails at their level length, and each 8 ft section drops 19-3/16 in at a 20% slope. The fence picket calculator cuts each picket to follow the ground at 2 in clearance, so the longest pickets need 72 in stock instead of 48 in.

Scalloped and Arched Picket Tops

Dog-ear pickets are sold by length to the tip, so a dog-ear top doesn't change the cut length. Scalloped and arched tops do, because each picket in a section is cut to a different height along a curve.

A scalloped top dips in the middle of each section. With a 6 in curve on a 4 ft fence, pickets run from 45-3/4 in near the posts down to 40 in at the center, all cut from 48 in stock.

An arched top peaks in the middle instead. With the same 6 in curve, pickets run from 40-1/4 in at the posts up to 46 in at the center. Either way, the fence picket calculator lists a cut length for every picket so each section matches the next.

Fence Length From Pickets You Have

Pickets on hand can be turned back into fence length. Holding back 10% for culls leaves 227 usable boards out of 250, and at 3-1/2 in with a 2 in gap those cover 103.9 ft, or 31.66 m, of fence.

That reverse count helps when finishing a run with leftover stock or matching a section to a sale bundle. A fence picket calculator gives the same answer either way, since pickets and length are tied through the picket-plus-gap pitch.

Pool Fence Picket Spacing

Pickets on a pool barrier can be no more than 1-3/4 in apart when the rails are under 45 in apart, under the 2021 ISPSC Section 305, as summarized by the City of Prosper, Texas. That covers almost every picket fence with two or three rails.

The fence picket calculator checks the dry gap, not the installed one. A 2 in gap on wet pine opens to about 2-1/8 in and fails, while solid privacy boards that open 1/4 in pass. Horizontal board fences give children a ladder, so they make poor pool barriers whatever the gap.

Rails, Screws and Fence Waste

The fence picket calculator adds one rail per 24 in of height, so a 4 ft fence has 2 rails and a 6 ft fence has 3. A 100 ft run at 8 ft post spacing has 13 sections on 14 posts, which means 26 rail pieces. The two short rails for the last 4 ft section share one board, so you buy 25 rails 8 ft long.

Each picket takes two screws per rail, so 219 pickets on 2 rails need 876 screws, or 9 boxes of 100. Post holes and concrete for those 14 posts come from the Fence Calculator, which prices the full fence around the pickets.

In a fence picket calculator, waste is figured as a percentage of the installed count, rounded up to whole pickets. At 10%, 219 installed pickets become 241 to order, and the order of 241 pickets plus 9 screw boxes costs $614 at the starting prices.

Stain area on a picket fence is the picket faces, not the whole fence outline. The 100 ft, 4 ft spaced fence has 490 sq ft of wood to finish on both faces, which the Deck Stain Calculator turns into gallons.

Post holes come first on a new build. The Fence Post Depth Calculator sets hole depth and concrete, and deck railings use the Baluster Calculator or Spindle Spacing Calculator instead.

Picket Fence and Fence Panel Basics

A picket fence uses separate vertical boards fastened to rails, usually with gaps between them. Pre-built panels and loose pickets suit different jobs, mostly because of who controls the spacing and the run length.

What's the difference between a fence picket and a fence panel?

A picket is one board, while a panel is a pre-built section of pickets already fastened to rails, often 6 or 8 ft wide. Panels go up faster but fix the picket spacing, and loose pickets let you set the gap and match an odd run length exactly.

Does the calculator work in metric and imperial units?

Lengths can be entered in feet, inches, yards, meters, centimeters or millimeters, and gaps and widths in inches or millimeters. Picket marks show in both inches and millimeters, which suits searches from the UK, Australia and India.