Published August 17, 2026 · Updated August 23, 2026 · By Tupep
The choice is not really about the posts
People frame this as a strength question and then argue about wind. The honest version is that both spacings produce fences that stand up fine in normal conditions, and the real differences are cost per foot, how the rails behave over time, what stock lengths you can buy, and how the fence handles ground that is not flat. Picket count does not change at all, which surprises people.
The comparison formula
- Sections = run length / spacing, rounded up
- Posts = sections + 1
- Rails = sections x rails per section
- Holes = posts
- Total cost = (posts x post price) + (rails x rail price) + (holes x concrete cost per hole)
Run that twice, once at each spacing, and the difference is your answer. Use your own prices; the ones below are placeholders so the arithmetic is visible.
Worked example, 96 ft run
96 divides evenly by both 6 and 8, which makes the comparison clean.
- 6 ft spacing: 16 sections, 17 posts, 48 rails, 17 holes.
- 8 ft spacing: 12 sections, 13 posts, 36 rails, 13 holes.
At placeholder prices of 18 dollars per post, 7 dollars per rail and 18 dollars of concrete per hole (three 80 lb bags at 6 dollars):
- 6 ft: (17 x 18) + (48 x 7) + (17 x 18) = 306 + 336 + 306 = 948
- 8 ft: (13 x 18) + (36 x 7) + (13 x 18) = 234 + 252 + 234 = 720
The difference is 228 dollars on 96 ft, or 2.38 dollars per linear foot. On a 400 ft property line that is close to a thousand dollars, plus sixteen extra holes to dig. That is the whole cost case for 8 ft, and it is a real one.
| Run length | 6 ft: sections / posts / actual spacing | 8 ft: sections / posts / actual spacing |
|---|---|---|
| 50 ft | 9 / 10 / 5.56 ft | 7 / 8 / 7.14 ft |
| 75 ft | 13 / 14 / 5.77 ft | 10 / 11 / 7.50 ft |
| 96 ft | 16 / 17 / 6.00 ft | 12 / 13 / 8.00 ft |
| 100 ft | 17 / 18 / 5.88 ft | 13 / 14 / 7.69 ft |
| 150 ft | 25 / 26 / 6.00 ft | 19 / 20 / 7.89 ft |
The rail stock argument nobody makes
This is the detail that quietly decides the job. At 8 ft spacing you are using 8 ft rails, and an 8 ft rail spanning post center to post center is exactly 96 in. A 4×4 post is 3.5 in wide, so each rail end gets 1.75 in of bearing on the post before the next rail butts into it. That is a butt joint at every single post, on every rail course, with almost no wood behind it. It works, but nothing is continuous and every joint is a hinge.
At 6 ft spacing you can buy 12 ft rails and span two bays with one board. Now half your posts have a rail running continuously past them instead of a joint on them, and the rail line is far stiffer. A 12 ft rail is also usually cheaper per foot than an 8 ft rail. That single change is why a lot of fence crews who do 6 ft spacing swear the fence lasts longer, and they are not wrong, they just are not describing it accurately.
There is also plain sag. A 2×4 rail laid flat, which is how most privacy fences do it so pickets have a wide nailing surface, is a shallow beam carrying a row of pickets. Over 6 ft it stays reasonably straight for years. Over 8 ft, especially the bottom rail with wet pickets hanging off it, it bows down over time. Turning the rail on edge fixes most of that but makes picket attachment awkward.
Where 8 ft wins and where it loses
| Situation | Better choice | Why |
|---|---|---|
| Long flat property line, budget matters | 8 ft | Fewer posts, fewer holes, lowest cost per foot |
| Rolling or sloped ground | 6 ft | Shorter bays step grade in smaller, less visible drops |
| 6 ft solid privacy in a windy spot | 6 ft | Less sail area between supports |
| Prefab panels | Whatever the panel measures | The panel dictates spacing, not you |
| Rocky soil, hand digging | 8 ft | Every hole avoided is real labor saved |
| Heavy gates in the run | Either, but upsize gate posts | Spacing does not change gate post loads |
The panel row deserves emphasis. If you are buying prefab panels rather than stick building, measure an actual panel before setting a single post. Panels sold as 8 ft frequently measure 92 to 93 in so they fit between posts set 96 in on center. If you set posts at a true 96 in clear opening for a 92 in panel, you have a 4 in problem at every bay. We measure the panel in the store aisle, not in the driveway.
Code, wind and the honest caveat
Post size, embedment depth and sometimes maximum spacing for solid fences above a certain height are set by local code, and frost depth varies by region. Some jurisdictions in high wind areas have specific requirements for solid privacy fences and will want a permit. Confirm all of it with your building department before you commit to a spacing, because a fence that has to be redone at 6 ft spacing after being set at 8 ft is not a fence, it is a new fence.
When nothing else decides it, we go 8 ft on flat ground with three rails and good posts, and 6 ft anywhere the ground moves, the wind blows, or the fence stands over 6 ft tall. Then check the panel dimension and the local code, and change the answer if either says so.
Related guides
- Gate Framing: What the Calculator Does Not Count
- Fence Materials for a Quarter-Acre Backyard
- How Many Posts and Pickets for a 100 ft Privacy Fence
- Composite vs Wood: Board Length and Waste
Sources and Further Reading
Run your own numbers with the Fence Calculator, or browse every tool on the calculators index. Coverage figures and material constants are cross-checked against manufacturer technical data sheets before publication. See our Methodology page for how figures are selected and verified.
Planning estimate only. Results assume standard conditions and are intended for material planning. Verify against your product’s technical data sheet and your local building code before purchasing. Structural, electrical, and gas work should be specified by a licensed professional.
Last updated: August 23, 2026
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