Methodology
Every FenceForge calculator runs the same deterministic engine. This page documents the calculation methods, the price method, and the limitations — so you can check our math.
Calculation methods
Posts
Each fence run is divided by the post spacing and rounded up to whole spans, then one post is added per run boundary. Runs form a chain, so a corner shared by two runs is counted once. Terminal posts (end, corner, transition, house connection) are reported separately from line posts. Every gate adds two posts: a hinge post and a latch post.
Panels & sections
Pre-assembled systems (vinyl, aluminum) are divided by panel width and rounded up. Board-built wood is counted by post-spacing spans, because the rails run between posts.
Pickets
Pickets per linear foot = 12 ÷ (picket width in inches + gap in inches). Only systems that actually use pickets output them — chain-link and pre-assembled aluminum systems never do. The waste factor is applied to pickets and rails, not to whole panels.
Rails
Rails = spans × rails-per-section (3 for privacy builds, 2 for open styles), times the waste factor, rounded up. Pre-assembled panel systems include their rails in the panel price, so no separate rail line is shown.
Chain-link fabric & top rail
Fabric comes in 50 ft rolls per fence height: rolls = ceil(effective run length ÷ 50). Top rail pipe comes in 10'6" sticks: sticks = ceil(effective run length ÷ 10.5). Gate openings are subtracted before both calculations.
Concrete
Concrete is calculated from volume, not a flat "bags per post" rule: hole volume (cylinder, from hole diameter and depth) minus the post's own displacement, divided by the bag yield (40 lb ≈ 0.30 ft³, 50 lb ≈ 0.375, 60 lb ≈ 0.45, 80 lb ≈ 0.60), rounded up per post. Post depth defaults to the quick rule — 1/3 of the above-ground height with a 2 ft minimum — unless you enter a depth or your frost line requires more.
Price method
Default unit prices are conservative national averages assembled from public home-improvement and installation cost surveys. They are estimates, not quotes. The full dataset — material, unit, price, source and date — is published on the open price dataset page. You can override any unit price in the cost calculator and save it as "My Pricing" in your browser.
Waste method
A waste factor (default 10%) is applied to cut materials — rails, pickets, fabric — to cover cutting losses and damaged boards. It is deliberately not applied to whole panels, posts or concrete bags.
Limitations
- Estimates are planning figures, not quotes or engineering specifications.
- Post depth and concrete figures must be verified against local code, frost depth, soil conditions and manufacturer requirements.
- Slopes, rocky soil, curved runs and custom gates change real-world quantities.
- Default prices are national averages — regional pricing is on the roadmap.
Review process
Formulas and price data are reviewed whenever a new fence system model is added and at least quarterly otherwise. Each change updates the price dataset's "last verified" date. Found an issue? Every calculator result shows the exact formula behind each line so errors are easy to report.