Fence Calculator
Plan a fence from end to end.
Enter the run length, post spacing and fence height and get the number of posts and sections, rail material, picket count, the post length you need to buy, and the concrete to set them.
Gate posts are added to the count, and post length allows for the buried portion.
How to use the fence calculator
Enter the total fence length and post spacing.
Set the fence height, style and gate count.
Read posts, sections, boards and concrete.
Why use the Build Tally fence calculator
Gate posts counted
Extra posts added automatically for each gate.
Post length advice
Tells you what length to buy, not just how many.
Concrete included
Bag count for setting every post.
Picket counting
Board and gap widths accounted for.
Posts, sections and the plus one
A fence run is divided into sections between posts, and the post count is always one more than the section count — plus one extra per gate, since a gate needs a post on each side. An 100 ft run at 8 ft spacing is 13 sections and 14 posts, or 15 with a gate. Missing the plus one is the most common fencing estimate error, and it leaves you a post short on the last day.
How long the posts need to be
About one third of a post's length should be underground. A 6 ft high fence therefore needs 9 ft posts set 3 ft deep. In cold climates the hole must also reach below the frost line, whichever is deeper. Corner and gate posts take more load than line posts and are often set deeper, wider, or in a larger diameter — worth planning before you order.
Concrete and setting
Allow roughly two 80 lb bags per post for a typical 10 inch × 30 inch hole with a 4×4 post. Put 4–6 inches of gravel in the bottom of each hole for drainage, crown the concrete above grade and slope it away from the post so rain runs off. Set and brace all posts, let them cure, then attach rails and boards — trying to do it in one pass rarely ends up straight.
Read the guide: How Much Gravel Do I Need? Tons, Cubic Yards and the Right Depth
Frequently asked questions
How many fence posts do I need?
Divide the run length by the post spacing and add one, then add one more for each gate. Enter your figures above for the exact count.
How far apart should fence posts be?
Six to eight feet is standard. Closer spacing gives a stiffer fence and is worth it in windy locations.
How long should fence posts be?
About one third longer than the fence height, so a 6 ft fence needs 9 ft posts set 3 ft deep — deeper if the frost line requires it.
How much concrete per fence post?
Roughly two 80 lb bags for a 10 in × 30 in hole with a 4×4 post.
How many pickets do I need?
Divide the fence length by the picket width plus the gap. The calculator does this when you choose the picket style.
Should gate posts be bigger?
Yes. Gate posts carry swinging load and are usually larger, set deeper and in more concrete than line posts.
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