A picket count is one division with two decisions inside it. Divide the length of the run by the width of a picket plus the gap you intend to leave, and round up. The decisions are the gap, which is a design choice that changes the count materially, and whether the fence is board on board, which overlaps every picket and can increase the count by a third or more for the same run.
How many fence pickets do I need? The run divided by picket plus gap
Measure the run in inches, decide the picket width and the gap, and divide. A closed board fence with no gap is simply the run divided by the picket width. Do it per section rather than for the whole fence if the sections differ, because rounding up once per section is not the same as rounding up once overall.
Board on board changes the arithmetic
Board on board overlaps each picket over its neighbour, so the effective coverage of each picket is its width less the overlap. Decide the overlap first, then divide the run by that effective width. A section that takes a dozen pickets butted will take several more overlapped, which is the difference people discover at the merchant.
Fence post calculator: posts, rails and the things that are not pickets
A fence post calculator is the other half: posts at the spacing your design allows plus one at each end and each corner, rails per section, and concrete per hole. A privacy fence calculator and a chain link fence calculator differ in the panel and the mesh but not in this: the count of pickets or panels is the easy part and the posts decide the labour.
Questions people ask about fence picket calculator
What gap should I enter in a fence picket spacing calculator?
It is a design choice, and it also depends on the timber: green timber shrinks and a tight fence becomes a gapped one. Decide the gap, state it on the estimate, and calculate from it rather than from a default.
How many pickets per 8 foot section, board on board or butted?
It depends on the picket width and the gap, and on whether the fence is board on board. Divide ninety six inches by the picket width plus the gap for a butted fence; for board on board, divide by the effective covered width instead.
Do I need to allow for waste on pickets?
Less than for sheet materials, because pickets are used whole, but allow for a few damaged or badly bowed boards in any bundle and for the cuts at the end of a run that does not divide evenly.
Do a privacy fence calculator and a chain link fence calculator work the same way?
In the part that decides the price, yes. They differ in the panel and the mesh, but the count of pickets or panels is the easy part in both, and the posts, set at the spacing the design allows plus one at each end and each corner, with rails per section and concrete per hole, are what decide the labour.