How the fence calculator works
Posts = fence length ÷ post spacing, rounded up, + 1
Rails = (posts − 1) × rails per section
Pickets = fence length (in) ÷ (picket width + gap), rounded up
Concrete per post = hole volume − the part of the 4x4 post inside it
Worked example
A 100 foot fence with posts every 8 feet needs 14 posts and 13 sections, so 26 rails with 2 rails each. With 5.5 inch pickets and 1/2 inch gaps, 200 pickets. Ten-inch holes 30 inches deep hold about 1.15 cubic feet of concrete each around the post, so 14 posts need 30 bags of 80 lb mix with 10% extra.
Post length
Posts must be the fence height plus the depth in the ground. A 6 foot fence in 30 inch holes needs 8.5 foot posts, so the calculator lists 10 foot posts. Cut the tops level after setting them.
Fence styles
| Style | Gap | Rails |
|---|---|---|
| Classic picket | 1.5 to 3 in | 2 |
| Spaced privacy | About 0.5 in | 2 or 3 |
| Full privacy (board to board) | 0 in | 3 for 6 ft and taller |
Before you dig
- Call 811 a few days before digging so utility lines are marked for free.
- Confirm your property line and any HOA or city height limits.
- Use ground-contact rated posts and exterior screws or galvanized nails.
Common questions
How many fence posts do I need?
Divide the fence length by the post spacing, round up, and add 1 for the end post. 100 feet with posts every 8 feet needs 14 posts. Add posts for gates and corners.
How far apart should fence posts be?
6 to 8 feet is typical for wood fences; 8 feet matches standard rail length. Use closer spacing in windy areas or for heavy privacy fences.
How deep should fence posts be?
A common rule is about one third of the post's height above ground, and below your local frost line. Many 6 foot fences use holes 24 to 36 inches deep. Check local requirements.
How many pickets do I need for 100 feet?
With 5.5 inch pickets and a 1/2 inch gap, each picket covers 6 inches, so 100 feet (1,200 in) needs 200 pickets. A privacy fence with no gaps needs about 219.