DIYCalcLab

Fence Calculator

Estimate fence posts, rails, pickets or panels and post-hole concrete for any fence length, with gates and real post sizes.

✓ Method shownUpdated By DIYCalcLab Editorial TeamSources (3)How we calculate

Quick answer: A 100 ft privacy fence with posts every 8 ft and one 4 ft gate needs 14 posts, 38 rails, 221 pickets (5.5 in, 5% waste) and about 56 bags of 50 lb concrete. A 30 m panel fence (1.83 m panels, one 1 m gate) needs 18 posts and 16 panels. Posts = sections + 1, plus one per gate.

Region: US · USD · Imperial

Wood fences: 6–8 ft. UK panels are 6 ft (1.83 m) wide.

2 rails up to ~4 ft (1.2 m) high, 3 for 5–6 ft (1.5–1.8 m).

0 for privacy; 2–3 in (50–75 mm) for spaced pickets.

Spare pickets/rails for splits and offcuts; 5–10% is typical.

Advanced options (waste, sizes, price)

About 3× the post width is a common rule.

Often ⅓ of post height above ground, and below the frost line where frost applies.

A 4×4 is 3.5 × 3.5 in; UK posts are often 100 × 100 mm.

Result

Fence posts

14 posts

Sections
12
Pickets (incl. waste)
221
Rails (incl. waste)
38
Concrete (50 lb bags)
56
Show the math
  1. Fence minus gates = 100 ft − 4 ft = 96 ft
  2. Sections = 96 ft ÷ 8 ft → 12; posts = sections + 1 + gates = 14
  3. Pickets = length ÷ (picket + gap) × (1 + waste) → 221
  4. Concrete per hole = π r² × depth − post area × depth = 1.15 cu ft (+10%) → 4 bag(s)

Shopping list & cost

Shopping list
ItemSpecQtyCost
Posts3.5 in square14—
Rails8 ft long38—
Pickets / boards5.5 in wide221—
Post concrete50 lb bag56 bags (4 per post)—
Gate kit (hinges + latch)4 ft gate1—

Prices are what you enter under Advanced options. Estimates only — check stock and pricing with your supplier.

Diagram

Area diagramA rectangle with its two sides labelled for area calculation. A = a × b 12 ft 10 ft
Labels update as you type. Focus an input to highlight its dimension.

How to use this calculator

  1. Measure the full fence line, including where gates will go.
  2. Set post spacing: 6–8 ft for wood picket fences, or the panel width for panel systems.
  3. Enter the number of gates and their width; gate openings are subtracted from infill.
  4. Choose pickets or pre-made panels; for pickets set width and gap.
  5. Adjust hole diameter and depth under Advanced to match your soil and frost depth.

Method & assumptions

Formula
Sections = (Fence length − Gate widths) ÷ Post spacing, rounded up
Posts = Sections + 1 + Gates
Pickets = Infill length ÷ (Picket width + Gap) × (1 + waste %)
Concrete per post = π × (Hole Ø ÷ 2)² × Depth − Post area × Depth
Post spacing
centre-to-centre distance between posts
Hole Ø
post-hole diameter, often about 3× post width

Assumptions & limits

  • The fence is one straight run; each corner or end on a separate run adds a post.
  • Every gate adds one post (the other side shares a line post).
  • Concrete includes 10% extra for irregular holes.

Rounding: purchase quantities are always rounded up to whole bags, boxes, sheets or bundles. See our methodology.

Worked examples

Imperial: 150 ft, 6 ft privacy fence, 2 gates (4 ft), 8 ft spacing

  1. Infill = 150 − 8 = 142 ft → 17.75 → 18 sections
  2. Posts = 18 + 1 + 2 = 21; rails = 18 × 3 = 54 (+5% = 57)
  3. Pickets = 1,704 in ÷ 5.5 = 310 (+5% = 326)

Metric: 20 m of 1.83 m panels, no gate

  1. Sections = 20 ÷ 1.83 = 10.9 → 11 panels
  2. Posts = 12; concrete per 100 mm post in a 250 × 750 mm hole ≈ 29 L → 4 × 20 kg bags each

In depth: fence planning notes

Planning the line and the spacing

Start by marking the fence line with stakes and string, then measure along the string rather than along the ground. Gates take up part of the run, so subtract their widths before dividing by post spacing. A common spacing is 8 ft (2.4 m) for site-built wood fences, and 6 ft (1.83 m) for UK panel fences, where the panel width fixes the spacing. Closer spacing is stronger in exposed, windy locations.

Corners and ends need posts, and each gate adds a post because the gate needs one on each side. Sloping ground changes the picture: panels can be stepped, which may need taller posts on the downhill side, while site-built fences can be racked to follow the slope. Measure the horizontal length for spacing and allow for longer posts on steps.

Post holes and concrete

A rule of thumb is a hole about three times the post width and deep enough to set one-third of the post's height in the ground, or below the frost line where frost heave is a problem. For a 4 × 4 post with 6 ft above ground, that is roughly a 10–12 in hole about 2–3 ft deep. The concrete volume is the cylinder of the hole minus the part of the post inside it, which is why the calculator asks for both hole and post sizes.

Bagged concrete or fast-setting post mix is usually poured dry or mixed with a little water depending on the product; follow the bag instructions. Sloping the top of the concrete away from the post helps water run off. Some installers prefer compacted gravel for posts to improve drainage — in that case use the gravel calculator for the fill.

Before digging, contact your local utility locating service (811 in the US) and confirm property lines and any local height or permit limits. Fences on boundaries may need agreement with neighbours.

Reference table

Typical post spacing and rails
Fence typeSpacing / rails
Wood picket, up to 4 ft (1.2 m)8 ft (2.4 m), 2 rails
Wood privacy, 6 ft (1.8 m)6–8 ft, 3 rails
UK panel fence1.83 m (6 ft) panels
Vinyl / composite systemsper manufacturer (often 6–8 ft)

Key facts

4×4 post actual size
3.5 × 3.5 in
Post depth rule of thumb
⅓ of above-ground height, below frost line
10 in × 30 in hole, 4×4 post
≈ 1.15 cu ft of concrete

Tips & common mistakes

  • Call before you dig — utility locating is free in the US (811) and available in the UK and Australia.
  • Set end and corner posts first, then string a line for the rest.
  • Crown the concrete at the top so water runs away from the post.

Frequently asked questions

How many fence posts do I need for 100 feet?

At 8 ft spacing, 13 sections and 14 posts for a straight run; add one post per gate.

How many bags of concrete per fence post?

For a 10 in × 30 in hole around a 4×4 post, about 1.15 cu ft — three or four 50 lb bags, or two 80 lb bags.

How far apart should fence posts be?

Typically 6–8 ft (1.8–2.4 m) for wood fences. Panel fences use the panel width.

How deep should fence posts be?

A common rule is one-third of the above-ground height (about 2 ft for a 6 ft fence), and below the local frost line.

How many pickets do I need?

Divide the fence length by picket width plus gap. A 96 ft privacy run with 5.5 in pickets needs about 210, plus 5% spare.

Sources

  1. Quikrete – setting fence posts — checked 2026-10; verify before launch
  2. Call 811 – Know what's below (US) — checked 2026-10; verify before launch
  3. Forest Garden (UK) – fence installation guides — checked 2026-10; verify before launch

Default values (bag yields, coverage rates, densities) are typical figures from manufacturer literature. Always check the label on the product you buy.

Related calculators

Learn more in our guides

Cite or embed this calculator

DIYCalcLab. “Fence Calculator.” Oct 18, 2026. https://diycalclab.com/fencing/fence-calculator/

An embeddable version for blogs and contractor sites is planned.

Estimates only. Verify quantities with your supplier and local building codes. For structural, electrical or safety-critical work, consult a licensed professional. Full disclaimer.