Fence Board / Picket Calculator
Enter your fence dimensions, board width, and spacing to determine the exact number of pickets, rails, and posts needed for your fence project.
Estimate only — not professional advice. Always verify results independently before purchasing materials or beginning work. Terms of Use
What is Fence Board / Picket?
A fence board calculator determines the quantity of pickets (vertical boards), horizontal rails, and posts required for a fence of given length and height. This calculation is essential for accurate material ordering because fence projects involve hundreds of repetitive components where small measurement errors multiply into significant cost overruns or shortages. The primary calculation divides the total fence length by the combined width of one board plus one gap to determine the number of pickets. A standard privacy fence picket is 3.5 inches wide (the actual width of a nominal 1x4 board) with zero gap for full privacy. A semi-private fence might use 3.5-inch pickets with 1-inch gaps, while a traditional picket fence uses narrower boards with wider spacing. Rails are the horizontal members that span between posts and support the pickets. Standard fence sections are 8 feet long (matching common lumber lengths), with posts at each end. Most fences use 2 or 3 rails per section. A 6-foot privacy fence should use 3 rails (top, middle, bottom) for adequate support and to prevent warping. A 4-foot picket fence may only need 2 rails. Posts are spaced at 8-foot intervals for standard lumber rails. The number of posts equals the number of sections plus one (because the last section needs a post at both ends). Posts are typically 4x4 pressure-treated lumber set in concrete at a depth of one-third the total post length plus 6 inches of gravel for drainage. The waste factor for fence boards should be 10 percent minimum. Boards often have defects — warps, splits, or knots — that make them unusable. Gate openings require cut pieces, and natural terrain variations necessitate adjustments. For fences on slopes where boards must be individually cut to follow grade, increase waste to 15 percent.
How to Calculate
- Measure the total fence length in feet along the property line or desired fence path
- Decide on fence height (6 ft for privacy, 4 ft for decorative picket, 8 ft for security)
- Choose board width (3.5 inches for standard pickets, 5.5 inches for dog-ear boards)
- Set the gap between boards (0 for privacy, 1-2 inches for semi-private, 2-3 inches for picket style)
- Select rails per section (3 for fences 5 ft or taller, 2 for shorter fences)
- Review results and order materials with the included waste factor
Formula
Spacing per Board = Board Width (in) / 12 + Gap (in) / 12 Raw Pickets = ceiling(Fence Length / Spacing per Board) Number of Pickets = ceiling(Raw Pickets x (1 + Waste% / 100)) Sections = ceiling(Fence Length / 8) Rail Boards = Sections x Rails Per Section Total Picket Linear Feet = Number of Pickets x Fence Height Posts Needed = ceiling(Fence Length / 8) + 1 Standard fence sections are 8 feet, matching common lumber rail lengths. Posts are placed at each section boundary, so the count is always sections + 1.
Example Calculation
A 100 ft privacy fence, 6 ft tall, with 3.5" boards, 0" gap, 3 rails, and 10% waste: Spacing per Board = 3.5 / 12 + 0 / 12 = 0.2917 ft Raw Pickets = ceiling(100 / 0.2917) = 343 Number of Pickets = ceiling(343 x 1.10) = 378 pickets Sections = ceiling(100 / 8) = 13 Rail Boards = 13 x 3 = 39 boards Total Picket Linear Feet = 378 x 6 = 2,268 ft Posts Needed = ceiling(100 / 8) + 1 = 14 posts
Frequently Asked Questions
What size boards should I use for a privacy fence?
Standard privacy fence pickets are 1x6 (actual 5.5 inches wide) or 1x4 (actual 3.5 inches wide) cedar or pressure-treated pine. Dog-ear style uses 1x6 boards with the top corners clipped at 45 degrees. For board-on-board style fences that provide full privacy with some air flow, use 1x6 boards overlapped by 1.5 inches on alternating sides.
How deep should fence posts be set?
The standard rule is one-third of the total post length below ground. For a 6-foot fence using 8-foot posts, set them 24 inches deep. In frost-prone areas, posts should extend below the frost line (36-48 inches in northern climates). Always set posts in concrete with 6 inches of gravel at the bottom for drainage.
Should I use 2 or 3 rails?
Use 3 rails for any fence 5 feet or taller. Three rails prevent pickets from warping and provide structural rigidity against wind loads. For 4-foot or shorter fences, 2 rails are sufficient. Place rails at roughly 8 inches from top, 8 inches from bottom, and centered for the middle rail.
How much spacing between pickets for a semi-private fence?
A 1-inch gap between 3.5-inch pickets allows airflow while blocking most sightlines. For a more open look, 2-inch gaps reduce material cost by about 35% compared to full privacy. Shadow-box fences alternate boards on opposite sides of the rails with 1.5-inch gaps, providing privacy from direct angles while allowing airflow.
What is the best fence board material?
Western red cedar offers natural rot resistance and beauty but costs 2-3 times more than pressure-treated pine. Pressure-treated pine is the most economical option with a 15-20 year lifespan. Composite fence boards are maintenance-free and last 25+ years but cost 3-5 times more than wood. Redwood is premium but increasingly scarce and expensive.
How do I handle a sloped yard?
Two options: stepped (level sections that drop at each post) or racked (boards follow the slope). Stepped fences are easier to build and use standard pre-cut boards but leave triangular gaps at the bottom. Racked fences follow grade smoothly but require custom-cutting each board bottom. Stepped works best for steep slopes; racked works for gentle grades under 12 degrees.