Fence Calculator
Sections = length ÷ post spacing, rounded up; posts = sections + 1 + one per gate; rails = sections × rails per section; pickets = length ÷ (picket + gap). A 100 ft fence at 8 ft spacing with one gate needs 15 posts, 39 rails and about 0.92 ft³ of concrete a post. Concrete: Fence Post Concrete Calculator.
How it's calculated: Sections = ⌈length ÷ spacing⌉; posts = sections + 1 + gates; rails = sections × rails per section; pickets = length ÷ (picket width + gap); concrete = hole volume − post volume.
Result appears here
Fill in the fields and press Calculate.
Formula, calculation, assumptions and sources
Sections = ⌈ fence length ÷ post spacing ⌉; posts = sections + 1 + gates
Rails = sections × rails per section
Pickets = fence length ÷ (picket width + gap)
Concrete per post = π(d/2)² × hole depth − post cross-section × hole depth
Run the calculation to see each step with your own numbers.
100 ft fence, posts 8 ft o.c., 3 rails, 5.5" solid pickets, 1 gate, 10-in × 2-ft holes.
Sections = ⌈100 ÷ 8⌉ = 13; posts = 13 + 1 + 1 = 15
Rails = 13 × 3 = 39; pickets = 1,200 in ÷ 5.5 = 219
Concrete/post ≈ 1.09 − 0.17 = 0.92 ft³; total ≈ 13.8 ft³ ≈ 0.51 yd³
Bags: 13.8 ÷ 0.45 ft³ per 60 lb bag (Quikrete Concrete Mix 1101) ≈ 30.7 → buy 31, or 33 with the 5% allowance; check the yield printed on your bag
- Equal sections; the last section is rounded up to a full section (you'll cut rails to fit).
- One extra post per gate (gates hang on a beefier post and latch to another). Corner and end posts are counted in 'sections + 1'.
- Picket count assumes vertical pickets butted or evenly gapped; board-on-board or shadowbox needs ~1.5–2× — increase the picket width entry to the effective pitch.
- Concrete per post is the hole minus a nominal 4x4. To convert to bags, divide the total ft³ by the yield printed on your bag — for example, 0.45 ft³ per 60 lb bag of Quikrete Concrete Mix 1101.
- How deep should fence posts be?
- Set at least one-third of the above-ground post height, and always below the local frost line. A 6-ft fence usually means 2–3 ft of post in the ground.
- How many rails per section?
- Two for a fence up to about 5 ft, three for a 6 ft fence, and four for a tall or heavy fence. More rails keep long pickets from bowing.
- How do I count board-on-board pickets?
- The calculator assumes butted or evenly gapped pickets. Board-on-board and shadowbox overlap, so they use roughly 1.5 to 2 times as many — set the picket-width input to the visible pitch you want rather than the actual board width.
- How many fence posts for a 100 ft fence?
- 14 posts at 8 ft on centre: 100 ÷ 8 rounds up to 13 sections, plus one post to close the run. Add one post for each gate — 15 with a single gate.
- How many pickets for a 100 ft fence?
- For butted 5.5 in pickets, 1,200 in ÷ 5.5 in = 218.2 pickets for the exact run, or 230 with the default 5% allowance for split or warped boards. Spaced pickets need fewer: divide by picket width plus gap.
Layout & post embedment
Standard fence-framing layout (sections + one post; ⅓ post embedment). Hole volume is standard geometry.
Bag yield
60 lb pre-mix ≈ 0.45 ft³ yield. Quikrete Concrete Mix 1101; Sakrete High-Strength Concrete Mix.
About the Fence Calculator
The Fence Calculator turns a wood-fence line into a materials list — posts, rails, pickets and the concrete per post hole — from the fence length, post spacing, number of rails and picket size. It adds an extra post for each gate. For a solid privacy fence set the picket gap to 0; for board-on-board or shadowbox, increase the picket-width entry to the effective pitch. Post concrete is given in cubic feet — convert to bags with the yield printed on your bag.
What you enter
- Total fence length
- Post spacing (on-centre) — 6–8 ft typical. Closer spacing = stiffer fence.
- Rails per section
- Picket width — Actual width — a "1x6" picket is 5.5".
- Gap between pickets — 0 for a solid privacy fence; 2–3" for a spaced picket fence.
- Gates — Each gate adds one extra (heavier) post.
- Post-hole diameter — ≈ 3× the post width. 10–12 in for a 4x4.
- Post-hole depth — ⅓ of the above-ground post height, and below the frost line.
- Waste allowance — Default 5%. Adjust to your own allowance — the exact figure is always shown too.
What you get back
- Posts — shown as the exact figure and, separately, a recommended figure with your waste allowance added.
- Sections — the exact result of the calculation.
- Rails — shown as the exact figure and, separately, a recommended figure with your waste allowance added.
- Pickets — shown as the exact figure and, separately, a recommended figure with your waste allowance added.
- Concrete per post — Hole volume minus the post. A 4x4 in a 10-in × 2-ft hole ≈ 0.92 ft³ — about 2.05 bags at 0.45 ft³ per 60 lb bag of Quikrete Concrete Mix 1101. Total the concrete for all posts and round up once; check the yield printed on your bag.
- Concrete total — shown as the exact figure and, separately, a recommended figure with your waste allowance added.
The formula, a worked example, the assumptions behind it and the sources are shown in full below the calculator.
Related calculators
- Concrete Calculator for Fence Posts — Concrete volume to set a run of fence posts, allowing for the posts displacing concrete in each hole.
- Vinyl Fence Calculator — Vinyl fence panels, posts and caps for a fence line.
- Concrete Calculator — How much concrete a rectangular slab or footing needs, in cubic yards or cubic metres.
- Lumber Calculator — Lineal feet and piece count of dimensional lumber for a job.
Part of the Fencing calculators.