How to calculate fence materials
Every fence takeoff starts with the length of the run and the post spacing. From there the sections set the posts and rails, the picket width sets the boards, and the hole size sets the concrete. This fence calculator does each step and shows the numbers it used.
Posts = sections + 1 + one per gate
Pickets = fenced length (in) / (picket width + gap) x (1 + waste %)
Concrete per post = hole volume - post volume
Worked example: 100 ft of 6 ft privacy fence
At 8 ft spacing, 100 / 8 = 12.5, so 13 sections and 14 posts. A 6 ft fence takes 3 rails per section, so 39 rails. Privacy boards 5.5" wide with no gap cover the 1,200" run with 218.2 boards, or 240 with 10% waste. A 10" hole 24" deep holds 1.09 cu ft; take away the 4x4 and each post needs 0.92 cu ft of concrete, or 22 eighty-pound bags for the job.
Assumptions
- The fence is one straight run with gates inside it. Add a post for every extra corner or end, or wherever a gate splits the run unevenly.
- Rails: 2 per section up to 4 ft high, 3 up to 6 ft, 4 above that.
- Board on board: each board covers its width minus the overlap you enter.
- Bag yields are the typical figures printed on 80, 60 and 50 lb bags of concrete mix. Hole depth and diameter should follow local code and frost depth.
Building these for a living? See Bolster for fence contractors, or how digital takeoff and AutoCost turn measurements into priced estimates.
FAQ
How many fence posts do I need?
Divide the fence length by the post spacing, round up to get the number of sections, then add one post, plus one for each gate. 100 ft of fence at 8 ft spacing needs 13 sections and 14 posts. Corners and ends of separate runs each need their own post.
How many pickets do I need for a fence?
Convert the fence length to inches and divide by the picket width plus the gap. For 100 ft of privacy fence with 5.5" boards and no gap that is 218 boards, or 240 with 10% waste.
How many bags of concrete per fence post?
Work out the hole volume, subtract the post, and divide by the bag yield. A 10" x 24" hole with a 4x4 post needs about 0.92 cu ft, which is about 1.5 eighty-pound bags per post.
Should fence posts be 6 or 8 feet apart?
8 ft is standard for wood privacy and picket fences because rails come in 8 ft lengths. Use 6 ft for tall fences, windy sites, heavy boards or vinyl and metal systems that specify it.
Can I turn this into a fence estimate?
Yes. Add unit prices here for a material total. In Bolster, AutoCost prices fence materials with live regional costs and turns the takeoff into a proposal the homeowner can sign and pay a deposit on.
