Wood Fence Calculator
If you need to build a fence, but the numbers are getting over your head, ask our wood fence calculator for some help with the math!
The method
posts = bays + 1; pickets = run ÷ (picket width + gap)
Posts outnumber bays by one
A 100-foot fence at 8-foot spacing needs 13 bays and 14 posts, because both ends need one. Forgetting the last post is the classic error, and it is also why every gate adds a post rather than replacing one.
Rather than leaving a stub bay at the end, divide the run by the number of bays and space the posts evenly. Thirteen bays over 100 feet gives 7 feet 8⅔ inches each — comfortably within the strength of a 2×4 rail and far better looking than twelve 8-foot bays and a 4-foot remnant.
Bury a third of the post’s exposed height. A 6-foot fence wants 2 feet in the ground, so buy 8-foot posts; in soft soil or high wind, go deeper.