Fence Calculator
Run length and post spacing give sections, posts, and rails; your picket width and gap give the picket count; and the optional hole dimensions give setting concrete using the same displacement math as the post hole calculator. The counting convention — a shorter final bay, never a stretched one — is stated below and locked in tests.
Run, spacing, and parts
Example: 100 ft at 8 ft o.c. → 13 sections, 14 posts, 26 rails, 210 pickets (5.5 in + 0.5 in gap, 5% waste).
Boundary note: post embedment, frost depth, wind loading, and fence-height rules are code- and site-governed — check your local requirements. Hole dimensions here are your own; the concrete math only totals what they hold.
The convention, worked through
The worked fence: 100 ft at 8 ft on-center is ceil(100 ÷ 8) = 13 sections — twelve full bays and one 4 ft bay — so 14 posts and 26 rails at 2 per section. Pickets: each 5.5 in board + 0.5 in gap covers 6 in of run, 1200 ÷ 6 = 200 net, 5% waste → 210 pickets. Setting concrete, reusing the post-hole engine: 0.92 cu ft per hole × 14 holes + 10% = 14.18 cu ft — 38 bags of 50 lb mix. All computed at build time by the same engine wired to the form.
What is sourced, what is yours
The layout arithmetic is convention, stated plainly and locked by tests. The sourced facts are the ones borrowed from the concrete tools: manufacturer bag yields, the PS 20 dressed lumber sizes behind the 5.5 in picket and 3.5 in post defaults, and QUIKRETE's labeled hole-sizing guidance. Spacing, picket geometry, gap, waste, and prices are all yours.
Deeper on any piece
Per-hole concrete detail (round posts, bag pricing) lives in the post hole calculator — the same math, one hole at a time. Rails and pickets by the running foot are the linear feet calculator's specialty, lumber volume for priced-by-the-board-foot stock is the board foot calculator's, and a deck behind the fence starts at the deck calculator.
Frequently asked questions
How are posts counted when the run is not a multiple of the spacing?
The tool never stretches a span beyond your chosen spacing: sections = ceil(run ÷ spacing), and posts = sections + 1. A 100 ft run at 8 ft on-center is thirteen sections — twelve full 8 ft bays plus one 4 ft bay — needing 14 posts and, at 2 rails per section, 26 rails. The alternative (stretching twelve bays to 8.33 ft) would exceed the spacing your rails and panels are sized for, so the shorter last bay is the convention this site locks in and tests.
How are pickets counted?
Each picket plus its gap occupies (width + gap) inches of run, so the count is run ÷ (width + gap) with your waste percentage applied before rounding up. A 100 ft run with 5.5 in pickets (the dressed width of a nominal 6 in board per the PS 20 lumber standard) and 0.5 in gaps needs exactly 1200 ÷ 6 = 200 pickets before waste. Width and gap are always yours — board sizes and gap preferences vary.
Do posts and rails get waste too?
No — they are exact layout counts (you cannot break 5% of a post), so the waste percentage applies only to pickets, where cutting and the occasional split board actually consume extras. The default is a modest 5%, labeled as a convention and fully adjustable.
How much concrete per post?
Exactly the post-hole calculator's math, reused: hole cylinder minus the post below grade, times every post including gate posts. QUIKRETE's guidance — a hole 3× the post width, 1/3–1/2 of the above-ground height deep — is a labeled starting point; frost depth and embedment for your area come from the local building department.
Does the tool handle gates?
As posts, yes: enter the extra gate posts (typically 2 per gate for a sturdy hang) and they are added to the post and concrete counts. The gate leaf itself — a kit or a build — is outside a quantity count of the fence line.
Dimensions never leave your browser. Sources, conventions, and the estimating pipeline are documented on the methodology page.