Key Takeaways
- Standard 6-inch pickets with 1-inch spacing need 9 pickets per side of an 8-foot section, totaling 18 pickets for the complete board-on-board assembly.
- Picket width and gap size directly affect the count — narrower pickets or tighter spacing means more pickets needed to fill the same 8-foot span.
- Board-on-board fencing places pickets on alternating sides of the rails, so you must account for both the front and back faces when ordering materials.
- Starting your layout with a full picket on one end and ending with a full picket on the other creates a balanced, professional appearance.
- Measuring your actual rail span and doing a quick layout calculation before ordering prevents short counts and wasted trips to the supplier.
The Math Behind 9 Pickets Per Side
The calculation starts with your usable rail span. An 8-foot section sounds like 96 inches, but the actual space between posts is usually 94 to 95 inches once you account for post thickness and how the rails attach. Using 94 inches as a working number, you divide by your picket width plus the gap between pickets.
With 6-inch pickets and 1-inch gaps, each "unit" takes up 7 inches. Dividing 94 inches by 7 inches gives you roughly 13.4 units. However, board-on-board fencing alternates pickets front and back, so you're not filling the entire width with one continuous row. Instead, you place pickets on the front face, then offset pickets on the back face. This arrangement means each side gets approximately 9 full pickets, with the spacing working out so gaps on one side align with pickets on the other.
The reason you get 9 rather than 13 or 14 is that board-on-board uses two layers. Nine pickets on the front plus nine on the back creates the overlapping privacy effect the style is known for, and the math works because the gaps and pickets on each side create a balanced visual pattern.
How Picket Width Changes Your Count
If you're using 5-inch pickets instead of 6-inch ones, your unit size shrinks to 6 inches (5-inch picket plus 1-inch gap). That same 94-inch span now fits roughly 15.6 units, which translates to about 10 or 11 pickets per side depending on how you space the end pickets. Wider pickets — say 8 inches — create 9-inch units, and you'd need only 7 or 8 pickets per side to cover the same distance.
The takeaway is simple: measure your actual picket width, add your chosen gap size, and divide your rail span by that total. Round to the nearest whole number, then verify by laying out the pickets on paper or with a tape measure before you cut or order.
Spacing Choices and Their Effect on Picket Count
A 1-inch gap is standard and creates a balanced look, but some homeowners prefer tighter spacing for more privacy or wider gaps for a more open feel. A half-inch gap with 6-inch pickets creates 6.5-inch units, which means you'd need about 14 or 15 pickets per side. A 1.5-inch gap creates 7.5-inch units and drops you to about 8 or 9 pickets per side.
Wider gaps also mean less wood and lower material costs, but they reduce privacy and can make the fence feel less substantial. Tighter gaps do the opposite. The choice is yours, but once you decide on a gap size, recalculate your picket count before ordering materials. A half-inch difference in spacing can mean one or two extra pickets per section, and that adds up across multiple sections.
Starting and Ending With Full Pickets
Professional fence builders always start and end a section with a full picket, not a partial one or a gap. This creates a clean, symmetrical look and makes the fence easier to build because you're not trying to fit a 3-inch sliver of wood into the end of a section. It also looks intentional rather than like you ran out of space.
To achieve this, you may need to adjust your gap size slightly across the section rather than keeping it exactly 1 inch everywhere. For example, if your math says you need 9.3 pickets, you'd use 9 full pickets and distribute the extra space across the 8 gaps between them, making each gap slightly larger than 1 inch. The difference is usually small enough that it's not visible to the eye, and the section looks balanced and complete.
Board-on-Board Means Double the Pickets
This is the detail that catches people off guard. Board-on-board fencing requires pickets on both the front and back of the rails. If you're building one 8-foot section, you need 9 pickets for the front face and 9 pickets for the back face, totaling 18 pickets for that single section. If you're building a 50-foot fence with six sections, you're looking at 108 pickets total, not 54.
The back pickets are offset so they cover the gaps on the front side, creating the privacy and visual interest that makes board-on-board fencing popular. When you're ordering materials or calculating labor, always remember to double your per-side count. Some builders order all their pickets at once and cut them to length in batches, which is more efficient than trying to order front and back pickets separately.
Measuring Your Actual Rail Span Before Ordering
The 8-foot nominal measurement is a starting point, not a may provide. Your actual usable span depends on post size, how the rails attach to the posts, and whether the posts are perfectly plumb. A 4x4 post takes up 3.5 inches of width, so two posts in an 8-foot section eat up 7 inches, leaving 89 inches of actual span. Some builders account for this differently, so your span might be anywhere from 88 to 95 inches.
Before you order pickets, measure the actual distance between the inside faces of your posts. Lay out your pickets and gaps on paper using that real measurement, count how many you need, and add 10 percent for waste and mistakes. This takes 15 minutes and prevents ordering too few pickets or discovering mid-build that your spacing doesn't work.
Common Mistakes to Avoid
The most frequent error is forgetting that board-on-board uses two layers and ordering only half the pickets you actually need. The second mistake is using the nominal 8-foot measurement without measuring the actual span, which can leave you one or two pickets short. A third mistake is not accounting for picket width — assuming all 6-inch pickets are exactly 6 inches when they may be 5.75 or 6.25 inches depending on the mill.
A fourth mistake is not deciding on gap size before calculating. If you assume 1-inch gaps but your builder prefers half-inch gaps, your picket count changes. Finally, some people order pickets without accounting for waste. Pickets break, get cut wrong, or are damaged in delivery. Ordering 10 percent extra prevents a second trip to the supplier and keeps your project moving.
Frequently Asked Questions
Do I need the same number of pickets on both sides of board-on-board fencing?
Yes. Board-on-board alternates pickets front and back, so each side has the same count. For an 8-foot section with standard spacing, that's 9 pickets per side, 18 total. The back pickets offset the gaps on the front, creating the privacy effect.
What if my rail span is 95 inches instead of 94?
Recalculate using your actual measurement. With 6-inch pickets and 1-inch gaps, 95 inches divided by 7 inches per unit gives you about 13.6 units, which still translates to roughly 9 pickets per side. The extra inch usually gets absorbed by slightly larger gaps at the ends or a small adjustment to spacing.
Can I use different picket widths on the front and back?
Technically yes, but it's not recommended. Using the same width on both sides keeps the fence balanced and makes ordering simpler. If you use different widths, you'll need to recalculate for each side separately and order two different picket sizes.
How much extra should I order for waste?
Order 10 percent extra pickets beyond your calculated need. For 18 pickets per section, that's about 2 extra pickets. Pickets break during transport, get cut wrong, or are damaged during installation. Having extras on hand prevents delays and extra trips to the supplier.
Does the height of the pickets affect how many I need per section?
No. Picket height (usually 4 to 6 feet) doesn't change the count. Only the width of the pickets and the gap size between them affect how many you need to fill an 8-foot horizontal span.