Wood Fence Calculator: Pickets, Boards, and Materials

Why Picket Count Depends Entirely on Fence Style

You may have plugged your fence length into a generic calculator and gotten a picket count that turned out completely wrong once you actually started building. That's usually because the same fence length needs a wildly different number of boards depending on the style — a spaced picket fence, a butted privacy fence, and a board-on-board (shadowbox) fence all use different math entirely, even at the identical length and board width.

This calculator handles all three styles specifically, because using the wrong formula for your style is the single most common reason DIYers under-order lumber and end up on a second trip to the store mid-project.

Spaced Picket, Privacy, and Board-on-Board Explained

Three fence styles cover the vast majority of residential wood fences, and each has a distinct picket layout.

How to Calculate Posts, Rails, and Pickets (step by step)

The calculator above runs all five formulas automatically and switches between gap and overlap math based on which style you select.

A Worked Example: 150-Foot Fence, Three Styles Compared

Let's price out a 150-foot fence, 6 ft tall, with one 4-foot gate, using 5.5" boards — first as privacy, then as board-on-board.

That's 78 more boards for the exact same 150-foot fence just from switching styles — a real cost difference worth confirming before you commit to a look purely on appearance.

Post Spacing and Rail Count by Fence Height

What if you're not sure how many rails your specific fence height needs? 8 feet on-center is the standard post spacing for wood fencing in the US — it matches standard 8-foot rail lumber and keeps the fence rigid under normal wind. High-wind regions (coastal areas, open plains, hilltops) often tighten that to 6 feet for extra strength.

Post depth matters as much as spacing — bury at least one-third of the total post length, so a 6-foot fence needs 9-foot posts (6 ft above ground, 3 ft buried). In frost-prone regions, go below the local frost line instead if that's deeper than the one-third rule, or heaving can push posts out of alignment over winters.

Choosing Picket Width and Wood Species

What if you're not sure which picket width fits your project? Standard picket widths run 3.5", 5.5", and up to 11.5" for dimensional kiln-dried lumber, and the choice affects both the final look and your total picket count. Narrower 3.5" pickets (sometimes called a stockade style at 2.5-3.5") give a tighter, more traditional look and need noticeably more pieces per linear foot than wider 5.5" or 1×6 boards. Wider boards cover the same run with fewer total pieces, which can mean less labor and fewer vertical seams, though very wide boards (8"+) are more prone to cupping and warping over time as they dry and shrink.

Wood species affects both price and lifespan more than picket width does. Pressure-treated pine is the most budget-friendly and widely available option, typically lasting 15-20 years. Cedar costs more but resists rot and insects naturally without chemical treatment, commonly reaching 20-30 years of service. Whichever species you choose, always seal cut ends — end grain absorbs moisture far faster than face grain, and this is especially important for pressure-treated lumber, since the treatment process doesn't always fully penetrate a board's cut ends.

Concrete for Setting Posts

What if you've got your post count but aren't sure how much concrete to buy? Each post hole typically needs about 1-2 bags of pre-mixed concrete, depending on post size and hole diameter — a reasonable planning estimate is 1.5 bags per standard 4×4 line post, with gate posts and corner posts (which use larger 4×6 or 6×6 lumber) needing more per hole. For a 20-post fence like our worked example, that's roughly 30 bags as a starting budget, though it's worth rounding up slightly since running short mid-project means waiting on concrete to cure before continuing.

Gate posts deserve special attention beyond just concrete volume — they carry the repeated stress of a swinging gate and should use heavier lumber (4×6 or 6×6 rather than standard 4×4 line posts) set at least 36 inches deep, deeper than a typical line post needs.

Stick-Built vs. Panel Fencing From Home Depot or Lowe's

What if you're planning to buy pre-built fence panels instead of individual pickets? This calculator assumes stick-built construction — buying individual posts, rails, and pickets separately, which is how most cedar and pressure-treated privacy fences are built. Pre-built panel fencing, commonly sold at Home Depot or Lowe's in standard 6-foot or 8-foot sections, skips individual picket math entirely — you're simply buying complete panels sized to drop between posts, which simplifies ordering but offers less flexibility on exact spacing and gate placement. If you're going the panel route, measure your run in whole panel widths rather than using the picket formulas here, and round up to the next full panel for any remainder.

Common Mistakes to Avoid When Ordering Fence Lumber

• ✕Using the wrong formula for board-on-board. This style subtracts overlap instead of adding a gap — using the standard picket formula badly undercounts the lumber a shadowbox fence actually needs.
• ✕Forgetting to subtract gate width before calculating pickets. A common and expensive mistake — buying lumber for the full fence length including the gate opening leads to over-ordering, sometimes by a dozen pickets or more.
• ✕Using 2 rails on a fence taller than 6 feet. Taller fences need 3 or 4 rails for structural stability — 2 rails on a tall fence risks picket warping and rail sag over time.
• ✕Skipping the waste allowance. Boards split, warp, and have knots that aren't usable — always add at least 10% to your calculated picket count before ordering.
• ✕Using standard 4×4 posts for gates. Gate posts carry repeated swinging stress and should use heavier 4×6 or 6×6 lumber set deeper than standard line posts, or the gate will sag over time.