Fence Calculator
Calculate posts, pickets, rails, and concrete for your fence project.
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How to Calculate Fence Materials
Planning a fence project starts with accurate material estimates. Under-ordering means a second trip to the hardware store mid-project; over-ordering wastes money. This fence calculator breaks down every component — posts, pickets, rails, and concrete — so you know exactly what to buy.
Posts
Posts are the structural backbone of your fence. Divide total fence length by post spacing and add one: (100 ft ÷ 8 ft) + 1 = 13.5, round up to 14 posts. Post height = fence height + 1/3 (buried depth). For a 6-ft fence, use 9-ft posts buried 3 ft deep. In frost-prone climates, bury below the frost line.
Pickets
Calculate pickets per linear foot: 12 ÷ (picket width + gap). For 3.5-inch pickets with 0.5-inch gaps: 12 ÷ 4 = 3 pickets per foot. For 100 linear feet: 300 pickets. Add 10% waste for cuts and defects: 330 pickets. Standard picket length = fence height + ~3 inches to account for setting height above grade.
Rails
For a 6-foot fence: 3 rails per bay (one at top, middle, bottom). For a 4-foot fence: 2 rails per bay. Number of bays = number of posts − 1. Total rails = rails per bay × number of bays. Rails are typically 8-foot 2×4 lumber that spans between posts.
Concrete
Two bags of 80-lb concrete per post is standard for residential fences. For gate posts and corner posts — which bear more stress — use 3–4 bags per post. Mix in a wheelbarrow or use fast-setting concrete that can be poured dry around the post and watered in place.
Hardware and Extras
Don't forget: galvanized or stainless screws or nails (about 1 lb per 50 linear feet), post caps to prevent water damage, gate hardware if applicable, and stain or sealer for long-term protection. Cedar and redwood naturally resist rot; pressure-treated pine needs sealer to prevent checking and graying.
Frequently Asked Questions
With 8-ft post spacing: (100 ÷ 8) + 1 = 13.5, round up to 14 posts. With 6-ft spacing: (100 ÷ 6) + 1 ≈ 18 posts. Always add the +1 for the final post at the end of the run.
At minimum 1/3 of total post length — for a 9-ft post, bury 3 ft. In frost climates, bury below the frost line (often 36–48 inches) to prevent heaving. Use at least 2 bags of 80-lb concrete per post.
Depends on picket width. 3.5-inch pickets with 0.5-inch gaps: ~300 pickets per 100 feet. 5.5-inch pickets with 0.5-inch gaps: ~200 pickets per 100 feet. Add 10% waste.
Pressure-treated pine is the most affordable and widely available (treat cut ends with end-grain preservative). Cedar and redwood are naturally rot-resistant and attractive but cost 50–100% more. Composite fencing requires no maintenance but is the most expensive upfront.
Many municipalities require permits for fences over a certain height (often 6 feet). Check your local building department, HOA rules, and property survey to verify setback requirements before starting. Fence placement errors can be expensive to correct.