Short answer
A 120-foot side yard fence using standard 5.5-inch-wide pickets with a 0.5-inch gap between each board requires 240 pickets. Order 252 to include a 5% waste buffer for splits and end cuts. The same fence needs 16 posts, 15 rails (16-foot stock), and 32 bags of 60 lb concrete.
How this calculator works
The formula behind this count is straightforward: take the total fence length in inches, divide it by the combined width of one picket plus its gap, and round up to the nearest whole board.
The math in plain English:
120 feet × 12 = 1,440 inches of fence
Each picket unit = 5.5 in (board) + 0.5 in (gap) = 6.0 inches
1,440 ÷ 6.0 = 240 pickets exactly
There's no rounding needed here — 120 feet divides evenly at a 6-inch unit width. If your fence length or picket size changes, the calculator rounds up so you never come up short.
Inputs and what they mean:
- Fence length (ft): The total linear run of fence you're building, measured along the ground. Measure the actual string line, not the deed line. Account for gates by subtracting their widths before entering this number.
- Picket width (in): The actual (not nominal) width of the board you're buying. A standard dog-ear cedar board is sold as "6 inch" but mills to 5.5 inches actual. Use the real number, not what's printed on the store tag.
- Gap between pickets (in): The air space between adjacent boards. A 0.5-inch gap is the most common for residential wood fences — tight enough for privacy, loose enough to let wood swell in wet weather without buckling. Zero gap works on paper but creates a wall that holds moisture; most installers avoid it for wood.
Secondary outputs explained:
The calculator also computes the supporting materials you'll need for the same 120-foot run:
- Posts (16): Based on one post every 8 feet, plus an endpoint post. This is the structural standard for 6-foot cedar fence sections. Shorter panel spans (6 feet) are stronger in high-wind zones but increase post and concrete counts significantly.
- Rails (15 boards of 16-ft stock): A standard fence runs two horizontal rails per section — top and bottom. Fifteen 16-foot boards cover all 15 spans between 16 posts. If you're building a three-rail fence for extra rigidity or a tall privacy fence, multiply that number by 1.5.
- Concrete bags (32): Two 60 lb bags per post hole fills a 10-inch-diameter × 24-inch-deep hole reliably. Fast-setting concrete is standard for post work because you can backfill the same day. In frost-prone areas, dig below the frost line — deeper holes use more concrete per post.
- Linear feet of pickets (120 ft): This output confirms the total board footage you're covering. It's useful when comparing bulk lumber pricing quoted by the linear foot rather than per piece.
What the calculator doesn't do:
It doesn't adjust for slope. A fence running up a hillside can require 5–15% more pickets depending on how you handle the grade — racked panels (pickets stay plumb, top rail follows grade) versus stepped panels (sections step down in flat increments). If your side yard has a noticeable slope, add 8–10% to the picket count and recalculate post depth for the downhill end.
It also doesn't account for gate framing hardware, post caps, or picket fasteners. Budget roughly 3–4 screws or nails per picket; for 240 pickets that's 720–960 fasteners.
Recommended materials
For a standard 120-foot cedar privacy fence like this one, the material selection is relatively simple. Most homeowners mix cedar pickets with pressure-treated structural lumber — PT holds up better in ground contact while cedar's natural oils resist above-ground rot without chemical treatment.
- Cedar dog-ear picket 5/8 in x 5-1/2 in x 6 ft — the standard residential privacy picket; buy in units of 252 to cover your 5% waste factor
- Pressure-treated 4x4 in x 8 ft fence post — ground-contact rated; you need 16 posts for this run
- Pressure-treated 2x4 in x 16 ft fence rail — 15 boards covers the top and bottom rails across all 15 sections
- Quikrete fast-setting concrete (60 lb bag) — 32 bags at 2 per post hole; sets firm enough to brace posts within 4 hours
FAQ
How many pickets do I need for a 120-foot fence?
You need 240 pickets using standard 5.5-inch-wide boards with a 0.5-inch gap. That accounts for the full 120 feet of run with no waste factor applied. Order 252–255 to cover a 5% waste buffer.
How many fence posts do I need for 120 feet?
At 8-foot spacing, a 120-foot run requires 16 posts — 15 interior spans plus one endpoint post. Mark your layout before you dig so post spacing stays consistent and gates land on a full span.
How many rails do I need?
A standard two-rail fence on 120 feet needs 15 boards of 16-foot pressure-treated 2x4 stock. That covers both a top and bottom rail when you run them end-to-end across the 15 sections.
How much concrete do I need for the posts?
Plan on 32 bags of 60 lb fast-setting concrete — two bags per post hole for 16 posts. That gives enough material to fill a standard 10-inch-diameter hole dug 24 inches deep.
What size gap should I leave between pickets?
A 0.5-inch gap is the most common choice for residential privacy fences; it provides room for wood to expand in wet weather without creating visible gaps. If you want a true privacy fence, drop to 0-inch spacing and add roughly 11 pickets to the count.
Does the calculator include a waste factor?
The base count of 240 does not include waste. Add a 5% buffer — that's 12 extra pickets — to cover splits, bad knots, and cut-off ends, especially on a 120-foot run where end cuts at corners or gates add up.
What picket width is most common?
5.5 inches is the nominal width of a standard dog-ear fence board sold at most lumber yards. The actual milled width is typically 5.5 in, so this calculator uses the real dimension, not a nominal 6-inch label.
Does gate width affect the picket count?
Yes. Subtract your total gate width from the 120-foot run before using the calculator. A single 4-foot gate reduces the run to 116 feet and drops the count by about 8 pickets.
Can I use this calculator for a 6-foot-high fence versus a 4-foot fence?
Yes — fence height doesn't change the picket count along the run; it only changes the length of each individual picket you order. The calculator counts boards horizontally across the fence length regardless of height.
What's the best wood for side yard fence pickets?
Cedar is the most popular choice for exposed pickets: it resists rot and insects naturally, takes stain well, and stays stable through seasonal moisture changes. Pressure-treated pine costs less upfront but requires more prep before painting or staining.
How do I handle a corner in my fence line?
Add a post at each corner and treat each straight section as its own run. Run the calculator separately for each leg, then add the picket counts together. Corner posts count as endpoint posts for both sections they anchor.
How long does it take to install 240 pickets?
A two-person crew working at a steady pace can typically attach 80–100 pickets per day by hand with a nail gun. Expect the picket-hanging portion of a 120-foot fence to take two to three days, not counting post-setting cure time.