Sources & formulas

Every calculator on FencingCalcs rests on established arithmetic plus stable fence conventions. Unlike topics with a time dependency, “verification” here is mathematical: each formula is tested against known values and is therefore correct for good. Here are the technical foundations by area.

Identities & geometry

Posts & sections: sections = ceil(line ÷ spacing); posts = sections + 1 for a straight run, plus one per gate, end and corner.
Pickets & panels: pickets = ceil(line × 12 ÷ (width + gap)); panels = ceil(line ÷ panel width); whole units always round up with ceil().
Post-hole concrete: hole volume = π × (diameter ÷ 2)² × depth − the post cross-section × depth; bags per post = ceil(volume ÷ bag yield).
Unit identities: 1 acre = 43,560 ft²; 1 rod = 16.5 ft.

Quantity conventions (labeled typicals)

Post spacing: 6–8 ft on center for most fences; ~10 ft for chain-link line posts; ~1 rod for farm posts — labeled, adjust to your fence.
Picket widths & gaps: 3.5" and 5.5" nominal boards with a 0–2.5" gap — labeled, measure your product.
Panel widths: pre-built panels 6 or 8 ft wide; height bands 4/5/6/8 ft — labeled.
Post-hole depth: buried ≈ 1/3 of the above-ground height + a ~6" gravel base, hole diameter ≈ 3× the post width — labeled planning values, not a structural design.
Concrete bag yield: a 40 lb bag ≈ 0.30, a 50 lb ≈ 0.375, a 60 lb ≈ 0.45, an 80 lb ≈ 0.60 ft³ — labeled, confirm on your bag.
Stain coverage: ~150–200 sq ft per gallon per coat — labeled, confirm on the can.
Farm wire: woven-wire rolls ~330 ft, barbed-wire rolls ~1,320 ft (¼ mile) — labeled.
Waste / overage: ~10% for waste, corners and terrain — labeled default.

Cost tools

Every cost tool uses the prices you enter ($/linear ft, $/post, $/panel, $/gate, labor $, tear-out $, $/gal, $/ft wire) — no material or labor price is stored, so the site needs no maintenance. Cost bands are a labeled sanity guide.
Fence cost: total = (quantity × your $/unit + labor + add-ons(gates, tear-out, terrain) − discount) ×(1 + contingency).
Cost to fence an acre / yard: perimeter from area (square assumption) or your L+W → linear ft × your $/lf.

Material and labor prices, product dimensions, permit rules and local code vary by place and change over time — always confirm panel/picket dimensions and bag yield against your product, order a little extra (~10%) for waste, corners and terrain, call 811 before you dig, confirm the boundary with a licensed surveyor and your local ordinance, and get itemized written quotes from a licensed, insured fencing contractor (and, for load-bearing or high-wind work, a licensed engineer) before you commit.