TryBuildCalcFence Post Calculator (Count, Depth & Concrete)
Size your fence posts instantly.
🕒 Last updated: September 4, 2026
Inputs
ℹ️Total linear run — confirm against an actual property survey, not just a fence-line guess.
ℹ️Above-ground height — check local ordinance limits, which are often lower at front yards than back/side yards.
ℹ️Privacy: butted boards, 0 gap. Picket: real gap between boards. Board-on-Board: overlapped on both faces — uses more boards than privacy for the same run.
ℹ️4x4 is standard for most fences up to 6 ft; 6x6 gives more margin for taller fences, gate posts, or high-wind sites.
Waste
ℹ️Applied to rails and pickets — 10% is a common estimating default. Not applied to the fixed post or concrete bag counts.
Cost
Posts Needed
20
4x4, 9.0 ft each (3.0 ft buried)
Pickets / Boards Needed
361
Privacy (butted), 5.5" pitch
Posts & Footings
Sections (8 ft O.C.): 19
Footing hole: 10.5" dia × 3.0 ft deep
Concrete per post: 1.55 cu ft
Concrete bags (80 lb): 52
Rails & Pickets
Rails per section: 3 (1 per 24" of height)
Total rails (+10% waste): 63
Picket run length: 150 ft
Total pickets (+10% waste): 361
Assumptions Used
Standard US residential wood fence construction. Post count follows the same "one per spacing, minimum 2" on-center formula used elsewhere on this site — 6-8 ft O.C. is standard, tighter for softer soil or high-wind areas. Rail count follows the widely-used "one rail per 24" of height" rule (2 rails for a 4 ft fence, 3 for a 6 ft privacy fence). Post bury depth is a rule-of-thumb (buried = fence height ÷ 2, derived from "bury 1/3 of total post length") — always verify against your local frost line, which governs whenever it's deeper than this rule gives. Footing hole diameter assumes roughly 3× the post's own width; concrete volume subtracts the post's own cross-section from the hole. Picket/board count uses the entered style's effective pitch (0" gap for privacy, a real gap for picket, an overlap for board-on-board). Waste applies to rails/pickets only, not to the fixed post or concrete bag counts. This calculator computes material quantities only — it does not verify structural post embedment for wind load, local fence-height ordinances/setbacks, or property line surveys.
Bill of Materials
Main material: 20 pcs + recommended tools
+−
Bill of Materials
Main material: 20 pcs + recommended tools
Computed items reflect your entered length, height, and style; consumables below are general recommendations — actual needs vary by product and site conditions.
For Your Job
Fence Posts
Pickets / Boards
Rails
Concrete
General Tools & Consumables
Post caps
Galvanized or stainless fasteners
Gate hinges & latch hardware
Post level / string line
Post hole digger or auger
Circular saw / miter saw
Level
Tape measure
Gravel (footing drainage)
Safety glasses & work gloves
Diagram simplified for clarity (not to scale, 3 posts shown regardless of actual count) — picket spacing shown schematically for the selected style.
Looking for the verification checklist, reference tables, tips, or common mistakes?See the complete Wood Fence Calculator.
Fence post and footing sizing
Post count follows the standard on-center spacing formula; footing depth is a rule-of-thumb based on fence height (always check your local frost line), and concrete volume subtracts the post's own cross-section from the hole.
This page defaults to a 150 ft run at 6 ft height, 8 ft O.C. spacing — edit the inputs above to match your actual fence.
Wood Fence Calculator Formula: How Is It Determined?
Post, rail, and picket quantities, plus footing volume, calculated separately and combined into a material takeoff.
Step 1 — Posts & Footings
Posts = max(2, ceil(Fence Length / Post Spacing) + 1) + 2 per gate
Buried Depth = Fence Height / 2 (derived from "bury 1/3 of total post length")
Footing Hole Diameter = ~3 x Post Width
Concrete per Post = Hole Volume - Post's Own Cross-Section Volume
Post count follows the same "one per spacing, minimum 2" formula used for deck posts elsewhere on this site. Buried depth is a rule of thumb, cross-checked against a cited worked example (6 ft fence, 9 ft post, 36" buried) — your LOCAL FROST LINE always governs when it's deeper.
Step 2 — Rails
Rails per Section = ceil(Fence Height (in) / 24)
Total Rails = Rails per Section x Number of Sections
One rail per 24" of fence height — 2 rails for a 4 ft fence, 3 for a 6 ft privacy fence, 4 for 8 ft — a widely-used rule of thumb, confirmed against multiple independent sources.
Step 3 — Pickets / Boards
Effective Pitch = Picket Width + Gap (Privacy: 0 gap, Picket: real gap, Board-on-Board: negative gap/overlap)
Picket Run Length = Fence Length - Total Gate Width
Pickets = ceil(Picket Run Length (in) / Effective Pitch)
One formula covers all 3 styles — only the gap value changes: zero for privacy's butted boards, a positive gap for picket-style, or a negative gap (overlap) for board-on-board, which needs more boards since each one only advances the run by width-minus-overlap.
Worked Example
This example walks through your current inputs above, using the same steps as the Formula section.
Input Values Used
| Input | Value | Why it is used |
|---|---|---|
| Length / height | 150 ft / 6 ft | Sets post/rail/picket counts |
| Style | privacy | Sets picket pitch |
| Post spacing / size | 8 ft / 4x4 | Sets post count and footing size |
Step 1 — Posts & Footings
| Calculation | Result |
|---|---|
| Sections | 19 |
| Total posts | 20 |
| Buried depth / post length | 3.0 ft / 9.0 ft |
| Concrete bags | 52 |
Step 2 & 3 — Rails & Pickets
| Calculation | Result |
|---|---|
| Rails per section | 3 |
| Total rails (with 10% waste) | 63 |
| Effective picket pitch | 5.5" |
| Total pickets (with 10% waste) | 361 |
Therefore, this 150 ft, 6 ft tall privacy fence needs approximately 20 posts, 63 rails, 361 pickets, and 52 bags of concrete.
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Disclaimer: This calculator provides approximate results for planning and estimation purposes only. Actual requirements may vary based on site conditions, materials, workmanship, and local building regulations. Always consult a qualified engineer, architect, or construction professional before making final decisions.