Fence Picket Spacing, Post Quantity & Concrete Footing Calculator
A wood privacy fence needs correct post spacing and footing depth to resist wind load and frost heave, plus an accurate picket count based on your desired gap style. This calculator turns your fence line length, height, and spacing choices into a full materials list: posts, concrete, rails and pickets.
Build this 150 ft fence with 20 posts, 40 bags of concrete, 57 rails and 328 pickets.
| Metric | Value |
|---|---|
| Fence length | 150 ft |
| Fence height | 6 ft |
| Post spacing | 8 ft O.C. |
| Total posts | 20 |
| Hole depth | 2.00 ft |
| Concrete bags | 40 (50 lb bags) |
| 2x4 rails | 57 |
| Pickets | 328 |
- 1.
PostCount = ceil(FenceLength / PostSpacing) + 1 - 2.
HoleDepth = FenceHeight / 3 - 3.
PicketCount = ceil((FenceLength×12) / (PicketWidth + Gap)) - 4.
RailsCount = (PostCount − 1) × (Height≥6 ? 3 : 2)
How to Use This Calculator
1. Enter your details
Use the labelled fields and units that match your situation.
2. Calculate instantly
The result, visual comparison, and working update as values change.
3. Review your result
Check assumptions, then copy, print, or share the calculation.
Formula & step-by-step maths
- PostSpacing
- On-center spacing between posts (ft)
- Gap
- Gap between pickets (in)
How post spacing affects total post count
Post spacing is measured on-center (from the middle of one post to the middle of the next), and tighter 6 ft spacing needs noticeably more posts and concrete than 8 ft spacing across the same fence length, trading material cost for extra rigidity in high-wind areas.
Why post hole depth scales with fence height
Taller fences catch more wind load and need deeper footings to resist leaning or toppling over time — a common rule of thumb sets hole depth at about one-third of the total fence height, though local frost line depth may require going deeper regardless of fence height in cold climates.
Picket gap spacing and privacy trade-offs
Zero-gap 'privacy fence' spacing maximizes visual screening but blocks airflow and can increase wind load on the fence structure; adding even a 0.5-1 inch gap between pickets improves airflow and reduces the chance of wind damage while barely compromising privacy from a normal viewing distance.
Rail count and structural support
Fences 6 ft and taller typically use three horizontal rails (top, middle, bottom) per section for adequate picket support and rigidity, while shorter 4 ft fences can often get by with two rails since the pickets have less unsupported height.
Reference: posts and concrete by fence length (8 ft O.C.)
| Fence length | Posts needed | Concrete bags (2/post) |
|---|---|---|
| 50 ft | 8 | 16 |
| 100 ft | 14 | 28 |
| 150 ft | 20 | 40 |
| 200 ft | 26 | 52 |
| 250 ft | 33 | 66 |
| 300 ft | 39 | 78 |
Frequently Asked Questions
Three worked examples
Same engine, three different starting points — useful if you want to see how sensitive the answer is before you type your own numbers in.
Example 1: total fence line length 117 ft, fence height "4 ft"
On the lower / more conservative end. Build this 117 ft fence with 16 posts, 32 bags of concrete, 30 rails and 256 pickets.
Example 2: total fence line length 150 ft, fence height "6 ft"
A typical middle-of-the-road setup. Build this 150 ft fence with 20 posts, 40 bags of concrete, 57 rails and 328 pickets.
Example 3: total fence line length 195 ft, fence height "8 ft"
On the higher / more demanding end. Build this 195 ft fence with 26 posts, 52 bags of concrete, 75 rails and 426 pickets.
Quick answers about the Fence Picket Spacing
What exactly does the Fence Picket Spacing work out?
A wood privacy fence needs correct post spacing and footing depth to resist wind load and frost heave, plus an accurate picket count based on your desired gap style. You enter total fence line length, fence height, post spacing (on center) and picket width (plus 1 more optional details) and the result panel updates straight away, so you can compare two or three versions of the same question in a few seconds.
What do I need before I start?
Only 5 fields: total fence line length, fence height, post spacing (on center), picket width and picket gap spacing. Nothing else is needed and nothing is stored.
How post spacing affects total post count?
Post spacing is measured on-center (from the middle of one post to the middle of the next), and tighter 6 ft spacing needs noticeably more posts and concrete than 8 ft spacing across the same fence length, trading material cost for extra rigidity in high-wind areas. The same maths runs inside this page, so hand-checking the result on paper gives you the identical figure.
Why do two calculators give me different answers for fence Picket Spacing?
Taller fences catch more wind load and need deeper footings to resist leaning or toppling over time — a common rule of thumb sets hole depth at about one-third of the total fence height, though local frost line depth may require going deeper regardless of fence height in cold climates. Different sites pick different assumptions, so always check which method a calculator states before you trust the gap between two numbers.
What does the "Reference: posts and concrete by fence length (8 ft O.C.)" table on this page tell me?
It is the reference range this tool works against — 6 rows from "50 ft" (8) up to "300 ft" (39). Use it to sanity-check whether the number you just calculated sits where you expected it to.
Which fence height should I pick?
The dropdown offers 3 choices — 4 ft, 6 ft and 8 ft. Pick the one that matches your real situation rather than the one you would like to be true; fence height usually moves the final figure more than any other single input, so it is worth running it twice with the option above and below your guess.
Do I have to press a button or reload the page to see the result?
No. Fence Picket Spacing runs completely inside your browser, so the moment you change a value the cards recalculate — there is no submit step, no page reload and no waiting for a server round trip. That also means it keeps working on a weak or intermittent mobile connection.
Is it free, and do you keep what I type?
It is free with no sign-up, no app install and no usage limit. Nothing you enter into Fence Picket Spacing leaves your device — the calculation is JavaScript running locally, so there is no upload of your figures to DrHint or anyone else.
Can I use it on a phone?
Yes — the layout stacks to a single column on small screens and the number fields open the numeric keypad on both Android and iOS. Many people bookmark this page or add it to their home screen and re-open it whenever the question comes up.
Anything to be careful about with the result?
A 150 ft fence with 8 ft post spacing needs about 20 posts; picket count depends on width — using 5. Treat the output as a well-grounded estimate for planning, not as a professional, legal or medical decision on its own.
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