Your Result Explained: Exact Takeoff Breakdown
A 100-linear-foot, 6-foot-tall wood privacy fence is the classic residential boundary run along a single side property line or across the back of a suburban lot. Because a solid 6-foot zero-gap fence acts like a 600-square-foot sail in heavy wind gusts, every structural bay requires three horizontal 2×4 stringers and 30-inch-deep concrete footings.
Dividing 100 feet by 8-foot on-center spacing yields 12.5 sections, which rounds up to 13 structural bays supported by 14 pressure-treated 4×4×8' posts. With 3 horizontal rails per bay, you need 39 net rails—or 43 rails with a 10% cutting and culling allowance. Using standard 1×6 dog-ear pickets (5.5 inches actual width) butted edge-to-edge (0" gap), 1,200 linear inches requires 219 net pickets, or 240 pickets with 10% waste for knotty or bowed lumber. Fastening 240 pickets across 3 rails takes 1,440 exterior screws (2 per rail crossing), and setting 14 posts in 10" × 30" holes requires 17.72 cubic feet of concrete: 30 bags of 80 lb mix (or 40 bags of 60 lb mix).
Thirty 80-lb bags of concrete alone weigh 2,400 lbs (1.20 tons), and 14 treated 4×4s, 43 rails, and 240 pickets add roughly 1,600 lbs of lumber. Have the lumberyard deliver the complete package on a single boom-truck pallet.
Step-by-Step Math for 100 Linear Feet of 6 Ft Privacy Fence
Calculating bays, 4×4 posts, 2×4 rails, 1×6 pickets, screws, and 10"×30" post-hole concrete for a 100 ft fence with 10% waste.
- Calculate 8 ft bays and posts: ⌈100 ft ÷ 8 ft⌉ = 13 bays; 13 + 1 = 14 posts.
- Compute 2×4 rails (3 per bay): 13 bays × 3 = 39 net rails × 1.10 = 43 rails.
- Compute 1×6 pickets (5.5" actual width, 0" gap): (100 × 12) ÷ 5.5 = 218.18 net × 1.10 = 240 pickets.
- Calculate exterior screws/nails: 240 pickets × 3 rails × 2 fasteners = 1,440 screws.
- Compute concrete for 14 holes (10" dia × 30" deep): 14 × 1.1509 cu ft × 1.10 = 17.72 cu ft (0.66 cu yds).
- Convert concrete to bags: ⌈17.72 cu ft ÷ 0.60⌉ = 30 bags of 80 lb mix (or 40 bags of 60 lb mix).
Bottom Line: Order 14 (4×4×8') posts, 43 (2×4×8') rails, 240 (1×6×6') pickets, 1,440 exterior screws, and 30 bags of 80 lb concrete.
How This Scenario Is Calculated
We divide the 100 ft run by 8 ft post spacing to get 12.5 bays, rounding up to 13 bays (12 full 8-foot bays and one 4-foot terminal bay) and adding 1 end post to get 14 posts. Multiplying 13 bays by 3 rails per bay and adding 10% waste yields 43 horizontal 2×4 rails.
For the pickets, 100 ft × 12 = 1,200 linear inches; dividing by 5.5 inches actual width equals 218.18 net pickets, or 240 pickets with 10% waste. Each 10" × 30" post hole holds 1.3635 cu ft gross minus 0.2127 cu ft displaced by the 3.5" × 3.5" post = 1.1509 net cu ft per hole, totaling 17.72 cu ft (30 bags of 80 lb concrete) across 14 posts with 10% waste.
Bays = ⌈Length ÷ Post Spacing⌉ | Posts = Bays + 1 + Gates | Rails = ⌈Bays × Rails/Bay × (1 + Waste%)⌉ Pickets = ⌈[(Length Ft × 12) ÷ (Actual Picket Width In + Gap In)] × (1 + Waste%)⌉ Hole Concrete (ft³) = [π × (Dia/24)² − (3.5/12)²] × (Depth/12) × Posts × (1 + Waste%) Project-Specific Tips & Common Mistakes
Split the Final 12 Feet into Two 6-Foot Bays Instead of One 4-Foot Bay
Because 100 feet divided by 8 feet leaves a 4-foot remainder (twelve 8-foot bays + one 4-foot bay), professional fence builders adjust the last two bays to 6 feet each (eleven 8-foot bays + two 6-foot bays) so the end of the fence looks balanced and symmetrical.
Buy 10% Extra Pickets to Cull Warped and Split Boards
Big-box bundles of 1×6 pressure-treated or cedar dog-ear pickets routinely contain 15 to 20 boards with wane edges, loose knotholes, or propeller twist. Ordering 240 pickets for a 219-picket net run gives you 21 extra boards so every installed picket is straight.
Space Rails at 6", 32", and 58" From the Bottom of the Picket
Setting the bottom 2×4 rail 6 inches up from the bottom of the 72-inch picket and the top rail 8 inches down from the dog-ear tip prevents picket tips from cupping in the sun while keeping the bottom rail clear of wet grass.
Mistake Buying 6-foot 4×4 posts for a 6-foot tall fence
Recommended Fix: A 6-foot tall fence requires 30 inches of post buried underground plus 66 to 70 inches above ground—meaning you must buy 8-foot (96-inch) or 9-foot 4×4 posts, never 6-foot posts.
Mistake Setting all 14 posts in concrete before checking string-line alignment
Recommended Fix: Set the two end corner posts in concrete first, pull a tight mason line along the outer face of the posts, and mark exactly 8 feet on-center along the string so all 12 intermediate posts align perfectly without wandering.
Reference Coverage Table (Normal-Weight Portland Cement Concrete)
Compare how coverage changes across common depths for Normal-Weight Portland Cement Concrete (default planning density 4000 lbs/yd³):
| Depth | 1 Cubic Yard Covers | 1 Ton Covers | Yards / 100 sq ft | Tons / 100 sq ft | Bags (0.6 ft³) / 100 sq ft |
|---|---|---|---|---|---|
| 24 in | 13.5 sq ft | 6.8 sq ft | 7.41 yd³ | 14.82 tons | 334 bags |
| 30 in Active | 10.8 sq ft | 5.4 sq ft | 9.26 yd³ | 18.52 tons | 417 bags |
| 36 in | 9 sq ft | 4.5 sq ft | 11.11 yd³ | 22.22 tons | 500 bags |
| 42 in | 7.7 sq ft | 3.9 sq ft | 12.96 yd³ | 25.92 tons | 584 bags |
Reference Source: ACI 302.1R / ACI 318 (145–150 lbs/ft³) & Quikrete No. 1101 Technical Data Sheet.
Frequently Asked Questions
How many 4×4 posts do I need for a 100 ft fence?
At standard 8-foot on-center spacing, a 100-foot straight fence requires 14 posts (covering 13 bays). If you use 6-foot spacing for high-wind areas, you will need 18 posts (17 bays). Add 1 extra post if your 100 ft run includes a walk gate.
How many 1×6 pickets are in a 100 ft privacy fence?
With zero gap between 5.5-inch-wide 1×6 pickets, 100 feet requires 219 net pickets, or 240 pickets when adding the recommended 10% waste allowance for culling crooked boards.
How many bags of 80 lb concrete do I need for 14 fence posts?
For 14 posts set in 10-inch diameter holes dug 30 inches deep (with 10% allowance for hole over-digging), you need 30 bags of 80 lb concrete (roughly 2.1 bags per hole) or 40 bags of 60 lb concrete.
How many 2×4 rails do I need for 100 feet of 6-foot fence?
A 6-foot privacy fence requires 3 horizontal rails per 8-foot bay. Across 13 bays, that equals 39 net rails, or 43 eight-foot 2×4s including 10% cutting waste.
What is the typical material cost for 100 ft of 6-foot wood privacy fence?
DIY lumber, concrete, and fasteners for 100 linear feet of pressure-treated 6-foot privacy fence typically run $1,600 to $2,400 ($16 to $24 per linear foot), or $2,600 to $3,600 if using Western Red Cedar pickets and rails.