Method and guidance
How to use the fence materials calculator
- Enter one straight fence run and a maximum post spacing established by the design. Add explicit posts for known gates, corners, ends, or bracing needs.
- Optionally enter a gate opening. It is removed from picket or panel and rail length, but the calculator does not invent gate-post or hardware details.
- Choose individual pickets or prefabricated panels. Enter actual picket width plus gap or actual installed panel width, then a visible infill waste allowance.
- Enter horizontal rail rows, purchasable stock-piece length, and a separate rail waste allowance.
- Enter the round-hole diameter and concrete-filled depth, actual square-post width, concrete waste, and exact bag yield. Every post receives one modeled hole.
- Optionally price posts, infill units, rail stock pieces, and concrete bags. Review each exact requirement and whole-unit purchase boundary separately.
Formula and calculation order
All continuous dimensions normalize to meters. Fence layout and product purchasing remain separate from the reused post-hole concrete domain.
exact spans = fence run ÷ maximum post spacing
whole spans = round exact spans up
base posts = whole spans + 1
total posts = base posts + explicit additional posts
net infill run = fence run − optional gate opening
exact pickets = net run ÷ (actual picket width + gap)
exact panels = net run ÷ actual panel width
adjusted infill = exact infill × (1 + infill waste ÷ 100)
exact rail length = net run × rail rows
adjusted rail length = exact rail length × (1 + rail waste ÷ 100)
exact rail stock pieces = adjusted rail length ÷ stock-piece length
concrete = round-hole cylinders − centered square-post displacement
concrete with waste = exact concrete × (1 + concrete waste ÷ 100)Whole pickets or panels, rail stock pieces, and concrete bags each round up once after their exact adjusted requirements. Post, infill, rail, and concrete costs use those purchase quantities.
Independently verified worked example
A 100 ft straight run at no more than 8 ft between posts needs 12.5 exact spans, so the layout rounds to 13 whole spans and 14 base posts. Two explicit additional posts produce 16 total posts and holes.
A 4 ft gate leaves 96 ft of net infill. Pickets 5.5 in wide with a 0.5 in gap create a 6 in module. Exact demand is 192 pickets; 10% waste raises it to 211.2, so purchase quantity is 212 pickets.
Three rail rows across 96 ft require 288 ft before waste. Ten percent raises demand to 316.8 ft. At 8 ft per stock piece, exact demand is 39.6 pieces and purchase quantity is 40 pieces containing 320 ft.
Sixteen round holes 12 in in diameter and 30 in deep, each with a centered 3.5 in square post, require 28.013148… ft³ of exact concrete after displacement. Ten percent produces 30.814463… ft³. At 0.375 ft³ per bag, exact demand is 82.171903… and purchase quantity is 83 bags.
At $20 per post, $3 per picket, $12 per rail stock piece, and $7 per concrete bag, component costs are $320, $636, $480, and $581. Their partial total is $2,017.
Construction guidance and source boundaries
The Home Depot's fence-building guide tells builders to use actual picket width and desired spacing, keep spacing consistent, plan posts and gates, dig suitable post holes, consider frost depth, and set posts in concrete. Review The Home Depot fence guide (retailer project guidance).
QUIKRETE's setting-posts instructions describe a round hole, centered post, gravel where applicable, and product-specific concrete placement. Calculate My Project uses those as boundaries while requiring the user to enter actual hole and post geometry. Review QUIKRETE setting-post guidance (manufacturer instruction PDF).
QUIKRETE publishes concrete calculators and product yields. The initial 0.375 ft³ bag-yield value matches a documented 50 lb fast-setting mix yield already audited in the post-hole calculator, but users must verify their exact bag. Review QUIKRETE's calculator (manufacturer reference).
The Common Ground Alliance's 811 service explains that anyone planning to dig should contact 811 before work so underground utilities can be marked. Review 811 before-you-dig guidance (damage-prevention resource).
These organizations do not sponsor Calculate My Project. Their guidance supports visible planning and safety boundaries, not one universal fence design.
Common estimating mistakes
- Rounding fence length to a number of spacing intervals but forgetting the endpoint post or known additional gate and corner posts.
- Assuming a gate opening automatically adds the correct number, size, or type of posts and hardware.
- Using nominal picket or panel sizes instead of actual installed coverage, or forgetting that picket gap belongs in the repeating module.
- Applying one waste value to pickets, rails, and concrete even though cuts, stock lengths, and field hole variation are different.
- Pricing exact linear rail length while purchasing whole stock pieces, or pricing exact concrete volume while purchasing whole bags.
- Ignoring square-post displacement or subtracting displacement after the concrete waste allowance.
Limitations
Version 1 models one straight fence run. It does not lay out corners, turns, stepped grade, separate runs, terminal conditions, shared posts, braces, gates, arbors, columns, or changes in fence type or height.
Picket count divides net run by picket width plus gap. It does not subtract post widths, decide the final end gap, preserve a centered layout, model alternating boards, or optimize cuts. Panel count does not simulate brackets, posts, partial panels, or manufacturer layout constraints.
Rail length excludes the gate opening and uses one stock length. It does not identify splices, require joints at posts, optimize offcuts, choose rail dimensions, or calculate fasteners.
Concrete uses identical straight round cylinders with centered square posts through the entire concrete-filled depth. It does not choose hole geometry, footing size, post embedment, gravel base, frost protection, drainage, uplift, lateral resistance, or structural adequacy.
Cost excludes unpriced components, gates, hardware, fasteners, caps, trim, finishes, gravel, delivery, tax, tools, equipment, labor, disposal, surveys, utility locating, engineering, and permits.
Frequently asked questions
Does maximum spacing mean every span will equal that value?
No. The calculator finds the smallest whole span count that does not exceed the maximum across the full straight run. Actual layout may redistribute spans or require extra posts.
Does entering a gate create gate posts?
No. Gate width is removed from infill and rail length only. Add known gate posts through the explicit additional-post field and design gate framing and hardware separately.
Why do pickets use width plus gap?
Each repeated picket consumes its actual face width plus the intended clear gap. The formula does not separately adjust the final edge or subtract post widths.
Why are there separate waste values?
Picket or panel cuts, rail stock cuts, and concrete field variation have different causes and package boundaries. Separate inputs keep those assumptions visible.
Is the concrete calculation duplicated from the post-hole calculator?
No. Fence results call the same pure post-hole domain used by the published post-hole concrete calculator, including square-post displacement, waste, bag yield, whole-bag rounding, and cost.
Does the calculator determine a safe fence design?
No. A qualified design must establish spacing, post and rail sizes, embedment, hole geometry, wind and soil resistance, gates, bracing, frost response, and applicable code.