QuantityBench Fence Calculator
Enter your fence length and post spacing to estimate posts, rails, pickets, and concrete bags needed. Works in US or metric units.
Estimated materials
How this is calculated
This calculator works the way most fence contractors quote a job: from total run length and post spacing.
1. Sections: fence length ÷ post spacing, rounded up, gives the number
of fence sections.
2. Posts: sections + 1, since a post sits at both ends of the run.
3. Rails: sections × rail rows per section (e.g. a standard 3-rail fence
uses 3 rails per section).
4. Pickets: section width ÷ picket pitch (picket width plus gap),
rounded up, × number of sections.
5. Concrete: 2 bags of 50 lb (~22.7 kg) mix per post, a standard rule of thumb
for setting residential fence posts.
Gates are noted separately rather than automatically subtracted from post counts, since gate framing hardware varies — see the FAQ below.
Assumptions
- Assumes a straight run with even post spacing — corners and direction changes still need a post, which this tool doesn't add automatically.
- Post and rail counts don't change with units — a post is a post whether the run was measured in feet or meters.
- Concrete bag count is a rule-of-thumb per post, not an engineered footing calculation for tall or wind-loaded fences.
Worked example
A 100 ft fence run, 8 ft post spacing, 3 rail rows, 5.5" pickets with a 0.25" gap:
| Sections | 13 |
|---|---|
| Posts | 14 |
| Rails | 39 |
| Pickets | 221 (17 per section) |
| Concrete | 28 bags (50 lb each) |
Concrete calculator for fence posts
Each fence post hole typically takes 2 bags of 50 lb (~22.7 kg) quick-setting concrete mix — so the number of bags you need scales directly with your post count, not your fence's linear footage. For a 150 ft fence run at 8 ft post spacing:
| Posts | 20 |
|---|---|
| Concrete bags | 40 bags (50 lb each) |
That's the standard rule of thumb for residential wood or vinyl fence posts set in soil. Taller fences (over 6 ft), posts on a slope, or particularly loose or sandy soil often call for a wider hole and more concrete per post — check your fence material's installation guide or a local contractor if you're outside typical residential conditions.
How many fence panels do I need
Pre-built fence panels (common in 6 ft and 8 ft widths) work differently from post-and-picket framing: since one solid panel spans the gap between two posts, your panel count is exactly the calculator's "sections" result — you just enter your panel's width as the Post spacing value above instead of a picket-frame spacing. For a 120 ft fence run using 6 ft wide panels:
| Panels needed | 20 |
|---|---|
| Posts | 21 |
| Concrete | 42 bags (50 lb each) |
If your panels are 8 ft wide instead, enter 8 as the post spacing to get the right panel and post count for that size. The rail-row and picket fields above don't apply to solid panel fencing — ignore those results and use only sections, posts, and concrete bags for this case.
Frequently asked questions
How many fence posts do I need for 100 feet of fencing?
With posts spaced every 8 feet, 100 feet of fence needs 13 sections (100 divided by 8, rounded up), which means 14 posts — one more post than the number of sections, since posts sit at both ends of every section.
How far apart should fence posts be?
Wood fences typically use 6 to 8 foot post spacing. Vinyl and some metal fence systems can span up to 10 feet between posts. Check your specific fence panel or picket length before finalizing spacing.
How much concrete per fence post?
A common rule of thumb is 2 bags of 50 lb (about 22.7 kg) concrete mix per post for a standard residential fence post hole. Taller fences, larger posts, or harder soil conditions can require more.
How do I account for a gate in my fence plan?
This calculator lets you note the number of gates separately rather than silently subtracting materials, since gate framing varies a lot by hardware and width. Plan to reduce pickets and rails by roughly one section's worth per gate opening, and confirm exact gate post requirements with your gate hardware's spec sheet.
How many pickets do I need per section?
Divide the section width (in inches) by the picket pitch — picket width plus the gap between pickets — and round up. For an 8 ft section with 5.5" pickets and a 0.25" gap, that works out to 17 pickets per section.
Does this calculator work in metric units?
Yes. Switch the "Units" toggle above the form to Metric to enter fence length and post spacing in meters and picket width/gap in centimeters. Post, rail, picket, and concrete counts are the same either way — they're counts, not measurements.