THE MATH, MADE VISIBLE
How it works
For each fence-only run, sections = round up(length ÷ maximum usable span). An open run needs sections + 1 posts. Gate endpoints are already included in adjacent runs. Concrete is cylindrical hole volume minus square post displacement.
Real project examples
One straight run
100 ft of fencing with 8 ft usable spans needs 13 sections and 14 posts. A custom picket fence with 3 rails per section needs 39 rails before allowance.
A gate between two runs
40 ft of fencing + a 4 ft gate + 40 ft of fencing spans 84 ft total. At 8 ft spans, plan 10 panels and 12 posts before stock allowance. The two gate posts are included.
Before you buy
- Run lengths exclude gates. Add a run on the other side of each intervening gate; do not enter the total boundary as fence length as well.
- Panel width and maximum post spacing limit the span. Narrow final sections may require cutting; confirm the panel manufacturer permits it.
- Enter actual post width, not nominal lumber size. Concrete-filled depth excludes drainage gravel and unfilled soil above the concrete.
- The 0.60 ft³ bag yield is an editable example for 80 lb QUIKRETE Concrete Mix. Check the exact mix and bag size.
- This tool covers open straight runs. Closed loops, shared corners, slopes, gate hardware, utility clearance and structural/code requirements need a separate layout.
Questions worth asking
Are gate posts added twice?
No. The endpoints of the fence runs on each side of a gate are its posts. The gate width contributes to total boundary length but not fence panels.
Why is allowance not added to post count?
Posts describe the layout. Extra allowance applies to purchased panel, rail and picket stock; it does not create more structural bays.
Does the tool tell me how deep to dig?
No. Enter the concrete-filled depth after checking manufacturer instructions, ground conditions, frost depth and applicable local requirements.
Sources & assumptions
NIST · unit conversion factorsQUIKRETE · concrete quantity calculatorQUIKRETE · mix yield referenceLast reviewed October 1, 2026. Planning defaults are editable examples. Product labels and supplier information override them.