Your Result Explained: Exact Takeoff Breakdown
A 150-linear-foot, 4-foot-tall spaced picket fence is the quintessential front-yard perimeter or dog-containment enclosure. Unlike a solid 6-foot privacy wall, a 4-foot open picket fence uses narrower 1×4 gothic or Colonial dog-ear pickets (3.5 inches actual width) separated by a 2.0-inch open air gap, requires only 2 horizontal 2×4 rails per bay, and uses 6-foot 4×4 posts set 24 inches into the ground.
Across 150 linear feet at 8-foot post spacing, you have 18.75 sections—rounding up to 19 bays and 20 total 4×4×6' posts. Because a 4-foot fence uses 2 horizontal rails per bay, 19 bays require 38 net rails, or 42 rails with a 10% waste buffer. Each 3.5-inch picket plus its 2.0-inch gap covers a 5.5-inch repeating module: dividing 1,800 inches (150 ft) by 5.5 inches yields 327.27 net pickets, or 360 pickets with 10% waste. Fastening 360 pickets to 2 rails takes 1,440 screws (4 screws per picket), and setting 20 posts in 10" × 24" footings requires 20.26 cubic feet of concrete: 34 bags of 80 lb concrete (or 46 bags of 60 lb concrete).
Because a 4-foot spaced picket fence allows wind to pass through the 2-inch gaps and uses shorter 6-foot posts and 4-foot pickets, total lumber weight and cost per linear foot are roughly 35% lower than a 6-foot solid privacy fence.
Step-by-Step Math for 150 Linear Feet of 4 Ft Spaced Picket Fence
Computing bays, posts, 2-rail stringers, 1×4 pickets with 2" gaps, screws, and 10"×24" post-hole concrete for a 150 ft fence with 10% waste.
- Calculate 8 ft bays and posts: ⌈150 ft ÷ 8 ft⌉ = 19 bays; 19 + 1 = 20 posts (4×4×6').
- Compute 2×4 horizontal rails (2 rails/bay for 4 ft height): 19 × 2 = 38 net × 1.10 = 42 rails.
- Compute repeating picket module: 3.5" actual 1×4 picket + 2.0" gap = 5.5" per picket.
- Calculate total 1×4 pickets: (150 ft × 12 in/ft) ÷ 5.5 in = 327.27 net × 1.10 = 360 pickets.
- Calculate fasteners (2 screws per rail × 2 rails): 360 pickets × 4 = 1,440 exterior screws.
- Compute concrete for 20 holes (10" dia × 24" deep): 20 × 0.9207 cu ft × 1.10 = 20.26 cu ft (0.75 cu yds).
- Convert concrete to bags: ⌈20.26 cu ft ÷ 0.60⌉ = 34 bags of 80 lb mix (or 46 bags of 60 lb mix).
Bottom Line: Order 20 (4×4×6') posts, 42 (2×4×8') rails, 360 (1×4×4') pickets, 1,440 exterior screws, and 34 bags of 80 lb concrete.
How This Scenario Is Calculated
Dividing 150 feet by 8-foot post spacing gives 18.75 bays, which rounds up to 19 bays and 20 posts. Multiplying 19 bays by 2 rails per bay gives 38 net rails (42 with 10% waste). For the spaced pickets, each 3.5-inch 1×4 board plus its 2.0-inch gap occupies 5.5 linear inches—so 1,800 inches ÷ 5.5 inches = 327.27 net pickets (360 with 10% waste).
For the 24-inch-deep by 10-inch-wide post holes, each cylinder holds 1.0908 cu ft gross minus 0.1701 cu ft displaced by the buried 4×4 post = 0.9207 net cu ft per hole. Across 20 posts with 10% waste, total concrete volume is 20.26 cu ft, requiring 34 bags of 80 lb concrete.
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
Cut a 2.0-Inch Hardwood Spacer Block With a Handle Cleat
Measuring 360 individual 2-inch gaps with a tape measure guarantees cumulative drift. Screw a short T-handle onto a scrap block of wood ripped to exactly 2.0 inches wide so you can hang the spacer on the top rail, slide the next 1×4 picket snug against it, and drive your screws in seconds.
Check Small-Breed Dog and Pool Code Gap Rules
A 2.0-inch gap between 1×4 pickets looks classic and blocks medium and large dogs, but toy breeds and puppies can squeeze through a 2-inch opening. If you have a toy breed, reduce your picket gap in the calculator to 1.5 inches (which increases picket count to 396).
Pre-Stain or Prime All Four Sides of 1×4 Pickets Before Hanging
Spaced picket fences expose both narrow 3/4-inch edges of every picket to rain and UV light. Dipping or rolling primer/stain onto the 360 pickets on sawhorses before installation is three times faster than brushing inside 360 two-inch gaps afterward.
Mistake Forgetting to add the picket width + gap width together when dividing fence length
Recommended Fix: New DIYers sometimes divide fence length by picket width alone or forget that a 3.5-inch picket with a 2-inch gap repeats every 5.5 inches—meaning a spaced 1×4 fence actually uses the exact same number of pickets per foot as a zero-gap 1×6 privacy fence!
Mistake Digging 24-inch holes in northern Zone 3–5 frost climates
Recommended Fix: While 24 inches is sufficient for a 4-foot fence in southern and mild climates, frost heave in northern states will lift shallow footings. Increase hole depth in the calculator to 36 inches if your winter frost line is 30+ inches.
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 Active | 13.5 sq ft | 6.8 sq ft | 7.41 yd³ | 14.82 tons | 334 bags |
| 30 in | 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 1×4 pickets with a 2-inch gap do I need for 150 feet of fence?
Because a 3.5-inch actual 1×4 picket plus a 2.0-inch gap equals 5.5 inches per picket cycle, 150 feet (1,800 inches) requires 328 net pickets, or 360 pickets when including a 10% waste allowance.
How many posts and rails are needed for a 150 ft 4-foot picket fence?
At 8-foot post spacing, 150 feet requires 19 bays and 20 posts (4×4×6'). With 2 rails per bay, you need 38 net rails, or 42 eight-foot 2×4s including 10% waste.
How many bags of concrete do 20 fence posts take at 24 inches deep?
Twenty 4×4 posts set in 10-inch diameter holes dug 24 inches deep require 20.26 cubic feet of concrete (including 10% waste)—which equals 34 bags of 80 lb concrete or 46 bags of 60 lb concrete.
Can I use 1×6 pickets instead of 1×4 pickets for a 4-foot spaced fence?
Yes. Using 5.5-inch (1×6) pickets with a 2.0-inch gap creates a 7.5-inch repeating module, reducing your picket requirement for 150 feet from 360 pickets down to 264 pickets (including 10% waste).
What length 4×4 post do I buy for a 4-foot tall picket fence?
Buy 6-foot (72-inch) pressure-treated 4×4 posts if your post holes are 24 inches deep, or 7-foot to 8-foot posts if you must dig 36 inches deep for northern frost lines.