Fence Calculator
Estimate the materials for a wood privacy or picket fence: pickets, posts, rails and the concrete to set them — before you buy a single board.
Results
Add 5–10% for cuts and waste, plus extra posts for gates and corners.
How to Use This Fence Calculator
- Enter the total fence length in feet (measure along the fence line).
- Enter the height — the calculator assumes 2 rails up to 4 ft and 3 rails above.
- Set the picket width and gap. Use 0 gap for a solid privacy fence.
- Adjust post spacing and rail length to match your lumber.
The calculator divides the fence length by the picket spacing, divides by the post spacing, and multiplies the rail count by the fence length.
Post Spacing and Setting
Wood fence posts are most commonly spaced 8 feet apart on center. Use 6-foot spacing for tall fences, high-wind areas, or when using shorter rails. Posts should be set in holes about one-third the post height deep — for a 6-ft fence, that means roughly 2 ft of post below ground, with concrete or packed gravel around the base.
Pickets and Rails
- Picket math: total inches ÷ (picket width + gap), rounded up. A 100-ft fence with 5.5-in pickets and 0.5-in gaps needs 200 pickets.
- Rails: 2 rails for fences up to 4 ft, 3 rails for 5–6 ft. Rail boards are typically 8–16 ft 2x4s; longer boards mean fewer overlaps and less waste.
- Gates: each gate needs 2–4 extra posts depending on width. This calculator does not include gates — add them separately.
Concrete for Posts
Most 4x4 posts take about one 50 lb bag of quick-set concrete per post when set in a 8–10 in hole. Corner, gate and end posts take more — plan two bags each. If you prefer dry-set gravel, use about one 50 lb bag of crushed stone per post instead.
Frequently Asked Questions
How many pickets do I need for a 100 foot fence?
A 100-foot fence is 1,200 inches. With 5.5-inch pickets and a 0.5-inch gap (6 inches per picket), you need 200 pickets. With no gap, you need 219.
How far apart should fence posts be?
8 feet on center is the most common spacing for wood fences, with 6 feet used for taller fences or high-wind areas. Post depth should be about one-third of the post height.
How many fence posts do I need for 100 feet?
At 8-foot spacing, a 100-foot fence needs 14 posts: 12 full spans plus 2 end posts. Add extra posts for gates and corners.
How much concrete do I need per fence post?
Most 4x4 fence posts need about one 50 lb bag of quick-set concrete each, or two bags for deep-set corner and gate posts. Check the bag instructions for hole sizes.