Picket fence spacing: gap chart and worked examples

How much space should you leave between pickets?

For an open decorative fence, choose an appearance with a small physical sample, then calculate the actual gap that fits your measured opening. For a privacy fence, first check the selected material and its installation instructions: starting with no gap does not guarantee that wood will stay closed as it dries. There is no single gap in this guide that is suitable for every product or purpose.

Compare four gaps in the same opening

These are hypothetical layout inputs, not recommended construction dimensions: a 91.8-inch clear opening between Post faces, 3.5-inch actual picket width, one row of full-width pickets, and Equal mode with a gap at both ends. The table changes only the target opening. Counts exclude waste, Gates and hardware.

Equal mode chooses the whole-picket count whose solved gap is nearest the target. Notice that the two-inch target produces a gap slightly larger than two inches. A target is not a maximum allowable opening. These rows compare appearance and quantity; they do not establish a guard, pool-barrier or pet-containment limit. The zero-target row still has small gaps because 26 full pickets do not fill the opening exactly.

For a fixed count, calculate the gap as (clear opening − count × actual picket width) ÷ (count + 1). Use unrounded values for the calculation and measure marks from one origin; do not repeatedly add the table’s rounded decimals. Your opening may need a different count, even if the Posts look evenly spaced from a distance.

Keep clear gap and center spacing separate

Picket spacing describes the clear opening between neighboring picket faces. It is different from the on-center pitch, which includes one picket width as well as one Gap. With a 3.5-inch picket and a 2.5-inch opening, the pitch is six inches. If you put six inches into a field labeled Gap, you will get a much more open fence than that example. Measure the empty space you want, and enter the actual picket width in its separate field.

Begin with the default fence Plan, then replace the Run lengths and obstacles with your sketch. To compare appearances, try target Gaps of one, two and 2.5 inches while keeping the Member width and measured lengths fixed. Watch both the count and the Solved Gap. The planner is not choosing a design style for you; those variations let you compare how much open space and how many Members your specific Bay can support.

Make a physical sample before ordering

Place three actual pickets on a flat surface with temporary spacers between them. View the sample from the distance and angle where the fence will usually be seen. A two-inch opening can look different from an oblique angle because the picket thickness also affects the sightline. Check the face width across several pieces, and note whether decorative edges reduce the apparent width. The tool represents a rectangular Member of one uniform width, so the sample helps reveal details that the numeric model does not contain.

Write the chosen clear opening on the sample spacer. Also write the actual picket width, rather than only its nominal label. If you measured a 3.5-inch face, enter 3.5, 3 1/2, or 88.9mm. Do not enter 4 just because the stock is sold as a 1×4. Changing width later moves every mark, so settle that dimension before printing the strips. Keep one measured sample with your notes when comparing stock from a different supplier or batch.

Count gaps as well as pickets

Between two Posts, n pickets create n−1 interior gaps and two End Gaps. That is n+1 gaps altogether. If a Bay is 91.8 inches clear and holds 15 pickets at 3.5 inches each, the wood occupies 52.5 inches. The remaining 39.3 inches must fit into 16 openings. Equal mode therefore gives a Gap of 2.45625 inches. It is slightly smaller than a 2.5-inch target because the Bay accepts whole pickets, not a fractional count.

The six-inch pitch from the rough example cannot simply be repeated until the last picket. If you keep every interior gap exactly 2.5 inches, the same 15 pickets and 14 interior gaps occupy 87.5 inches. That leaves 4.3 inches for the two ends, or 2.15 inches each. Both arrangements conserve length, but they look different beside the Posts. The calculator exposes this choice as Equal versus Fixed so that the end treatment is deliberate rather than an accidental leftover.

Fit each Bay to its own opening

A Run with several intermediate Posts is not one uninterrupted clear length. First establish the Post positions and then measure or calculate each opening. In the default 40-foot Run with 3.5-inch Posts and an eight-foot maximum Bay, five openings are 91.8 inches clear. In the following 24-foot Run, the three openings are 91⅓ inches clear. Both groups use 15 pickets per Bay at the default target, but their exact Gaps differ. Use the Bay label on the drawing to identify the correct result.

When existing Posts are already installed, compare the planned opening with the physical one before marking. A Post that is slightly out of plumb can produce different opening widths at the upper and lower Rails. This version assumes parallel, straight boundaries; it does not taper the pattern or bend the Rails. Resolve that discrepancy in your construction plan before using a single set of marks. Repeatedly trimming an End Gap by eye defeats the point of a calculated equal layout.

Understand what a zero target means

Setting Target Gap to zero asks for the nearest feasible arrangement of whole-width pickets. If the Bay is not an exact multiple of the width, Equal mode can still produce a small Gap. The result is an arithmetic best fit, not a guarantee of privacy or weather-tight construction. A closed panel may require a deliberate rip, overlap or manufacturer-defined joint. Those choices have their own material and movement rules. Do not describe a zero-target row as a board-on-board layout.

For a second example, take a 72-inch clear opening and 5.5-inch actual boards. Thirteen boards occupy 71.5 inches, leaving half an inch. With a zero target, Equal mode spreads that half-inch across 14 gaps, about 0.035714 inches each. Fixed mode keeps the interior gaps at zero and puts 0.25 inches at each end. Neither arrangement fills every part of the opening with wood, and neither models future movement.

ProWood’s fence installation FAQ says its pressure-treated fence pickets shrink as they dry and advises placing them next to each other during installation to reduce the gaps that develop. That advice applies to the material described by that manufacturer; it is not a rule for every wood species, dry board, composite or premade panel. Check the instructions and condition of the product you will buy before choosing an initial gap. This calculator does not predict a final dry gap or simulate overlapping boards.

If your fence uses shadowbox pickets on opposite sides of Rails, calculate that system explicitly rather than doubling this page’s count without checking the edges and overlaps. The same caution applies to premade panels, angled infill and profiles whose effective width varies with installation. The planner models one repeated row inside each Bay. That boundary keeps the marks explainable: every left edge is a fixed start offset plus an integer multiple of Member width and the solved Gap.

Transfer the pattern from a fixed origin

Use the running-measurement list for the specific Bay. A left-edge mark places the near edge of a picket; a center mark places its midpoint. Choose one method for the entire Rail and label your reference side. Hook the tape at the Bay’s left inside face, then measure every mark from that same point. The calculator does not obtain later positions by adding a rounded fraction to earlier rounded positions. Neither should your marking procedure.

The screen rounds fractions to the nearest 1/16 inch for tape-measure readability. That can make the displayed Gap look identical in two Bays whose exact geometry differs slightly. The printable strips retain the original positions, and the final boundary mark identifies the full Clear Length. Check that boundary against the actual opening, then compare the first and last pickets in a dry layout. This catches a reversed origin or incorrect width before it becomes a complete row of misplaced fasteners.

Save the layout you actually measured

After checking the first and last pickets in a dry layout, save the inputs with Copy plan link. Print one Bay first: match Letter or A4 in the page controls and print dialog, select Actual size or 100%, and disable fit-to-page and browser headers. Measure the six-inch calibration ruler on the physical sheet before using the marks. A browser preview cannot establish your printer’s scale. Butt matching join lines without overlap, and regenerate the affected Bay if a Post moves.

For a whole-fence estimate, the 100-foot picket count guide explains why Posts and separate Bays change the total. If you are buying complete panels, use the panel width and Post spacing guide instead of treating a nominal panel label as a clear opening. The formula page documents the arithmetic behind the marks.

Separate appearance from construction requirements

The spacing comparisons here are layout examples. They do not establish permissible Post spacing, structural strength, property-line placement or a required footing. Check the selected product instructions and your local requirements before fixing the assembly. Keep a separate list for Gate leaves, hinges, latches and Post connections, because the planner’s Member and screw takeoff does not include that hardware. If the fence also serves as a required guard, use the applicable guard rules rather than treating a decorative picket target as a safety limit.