How much electric fence wire do I need for 1 acre?

A square acre is about 835 ft around. At three strands that's 2,505 ft of conductor, or 2,756 ft once you add 10% for corners, dips and terminations.

How many paddocks do I need for rotational grazing?

Rest days divided by grazing days, plus one for the paddock they're standing in. Thirty days of rest with three-day moves gives eleven paddocks; five-day moves give seven.

How many strands for horses, goats, cattle or deer?

Horses: three permanent, two seasonal, one interior. Goats and sheep: five, four, two. Cattle: two, two, one. Deer: three, at roughly 18, 34 and 50 inches. The perimeter counts for goats and cattle are manufacturer species guidance rather than extension guidance.

How much polywire for 5 acres?

A square five acres is about 1,867 ft around, so each cross-fence spans roughly 467 ft. If you own two reels and move them, that's about 1,030 ft of line out at once — one 1,640 ft roll covers it.

How many ground rods does an electric fence need?

Three at minimum: galvanized, 6 ft deep, 10 ft or more apart, for energizers up to 15 joules. Five up to 25 joules, seven up to 35.

What size energizer do I need?

Roughly one output joule per mile of total fence, doubled if grass and brush will touch the line. Size it low and the far corner is where you'll find out.

Electric Fence Calculator & Paddock Planner

The line

3,308 ft of line

Two 660 ft rolls + two 1,000 ft rolls of polybraid rope — $359.96

Amazon price on 2026-08-26 — check the listing for today’s.

The arithmetic

1,000 ft perimeter × 3 strands = 3,000 ft · +10% spare = 3,300 ft · +8 ft for gates = 3,308 ft

That’s about 1.38 acres inside the line.

3 strands · 2,000–3,000 V at the far corner · post every 20 ft.

Perimeter counts from the beginner setup guide (Virginia Tech Cooperative Extension SPES-689 lineage); the single interior strand from the rotational grazing plan.

Your list

Item	Qty	Each	Total
Polybraid Rope 660 ftB0DHD935HF	2	$69.99	$139.98
Polybraid Rope 1,000 ftB0DHD8HBK1	2	$109.99	$219.98
Jumper Leads + Grounding RodB0GKG8MLF3	1	$33.99	$33.99
Jumper Leads, 10,000 VB0GK1NRP5P	1	$17.99	$17.99
Grazeline total			$411.94

Amazon price on 2026-08-26 — check the listing for today’s.

More rolls means more joins, and joins want proper clamps — so there’s a second set of leads on the list.

Buy the list on Amazon ▸

Everything else your fence needs

We don’t sell it yet, so here’s what to look for.

Item	Count	Spec to look for
Line posts	about 46	T-posts or wood; step-ins for seasonal lines
Corner / end assemblies	4	Braced — corners do the real work
Insulators	about 138 + 12 strain	Rated for high voltage, matched to post type and conductor width
Energizer	1	Low-impedance, UL/IEC listed, at least 1 joules
Ground rods	3	Galvanized, 6 ft, 10 ft apart — not rebar, don’t mix copper and galvanized
Fence voltmeter	1	The only tool that tells you the truth. Non-negotiable.

Counted at one post every 20 ft. Walk your line before you buy — dips and rises change this more than arithmetic does.

At least 1 joules of low-impedance energizer and 3 ground rods, 6 ft deep, 10 ft apart, in soil that stays moist. Grounding is where most “weak fence” complaints actually live. the grounding guide has the procedure.

Loading the calculator…

Show your work

Every number on this page comes from one of these.

Take them with you. If our arithmetic and your pencil disagree, we want to hear about it.

Geometry

P = 2 × (L + W)

Rectangle from its two sides.Arithmetic.

P = 4 × S

Square from its side.Arithmetic.

P = 4 × √(43,560 × A) ≈ 834.8 × √A

Square from acreage. One acre is about 835 ft around.Arithmetic; matches the subdivision table in the rotational grazing guide.

W = √(43,560 × A ÷ r) · L = r × W · P = 2 × W × (1 + r)

Rectangle from acreage and a shape ratio.Arithmetic.

P = π × 2 × √(43,560 × A ÷ π) ≈ 739.8 × √A

Round-ish from acreage. A circle is the smallest perimeter for a given area, so we round up.Arithmetic.

Conductor

C_raw = P × strands

Perimeter times the number of strands.Arithmetic.

C_need = ⌈C_raw × (100 + spare) ÷ 100⌉

Add spare for corners, dips and terminations. Integer arithmetic, so the printed multiplication survives being checked on paper.5–10% is the published range; we default to the top of it.

C_gate = gates × 8 ft

Four feet of tie-off each side of every opening. A gate never subtracts from the perimeter.Arithmetic; the opening is bridged by a handle kit and buried insulated cable.

C_total = C_need + C_gate

What you buy.Arithmetic.

Hardware

N_line = ⌈P ÷ spacing⌉ − corners

Line posts. Default spacing: 15 ft for permanent tape, 20 ft for rope and wire, 25 ft for step-in posts on a line that moves.Tape catches wind, so it leans toward the closer spacing.

N_ins = N_line × strands · N_strain = corners × strands

Insulators, standard and corner/strain type.Arithmetic.

Power and grounding

miles = C_raw ÷ 5,280

All strands, tied together.Arithmetic.

J = max(1, roundUp₀.₅(miles)) · doubled under vegetation load

Energizer size in joules.About one joule per mile of fence, more with vegetation load. Doubling is the conservative reading of 'more'.

rods = max(3, table(J), ⌈3J ÷ 6⌉)

Ground rods: three up to 15 joules, five to 25, seven to 35 — cross-checked against three feet of rod in the soil per joule.Virginia Tech Cooperative Extension SPES-691; Michigan State University Extension E3470.

Paddocks

N = ⌈rest ÷ graze⌉ + 1

Paddock count. The +1 is the paddock currently being grazed.University of Maine Cooperative Extension pasture course, Lesson 6. The rounding up is ours, and it's there because rest is the number to protect.

A_p = A ÷ N

Paddock size.Arithmetic.

C_move = ⌈2 × W × strands × (100 + spare) ÷ 100⌉

Polywire out at once when you own two reels and move them.Arithmetic; the two-reel routine is what the rotational grazing guide describes.

C_all = ⌈(N − 1) × W × strands × (100 + spare) ÷ 100⌉

Polywire if every cross-fence stays up all season.Arithmetic.

C_lane = 2 × L × lane strands · L_cross = (W − lane width) ÷ 2

Central-lane layout: a permanent spine with short cross-fences hung off it. The lane is counted in both keep-out modes because the spine always stays up.USDA-NRCS (Virginia), Rotational Grazing System Layout Considerations.

The same table the rotational grazing guide prints

Published subdivision guidance next to what this calculator returns. They agree to within a rounding step, which is the point — a tool that disagrees with its own guides is a tool nobody should trust.

Area	Guide	This calculator
1 acre	835 ft	834.8 ft
2 acres	1,180 ft	1,180.6 ft
3 acres	1,450 ft	1,446.0 ft
4 acres	1,670 ft	1,669.7 ft
5 acres	1,870 ft	1,866.8 ft

Guides

Read this before you build

Three guides, no fluff, written from the same numbers this page used.

Guide 4

The Complete Beginner Setup Guide

Posts, insulators, strands, grounding, testing, first-day training — in order.

Read it →

Guide 6

The 1–5 Acre Rotational Grazing Starter Plan

Paddock count, polywire lengths, and the twenty-minute moving routine.

Read it →

Guide 5

How Many Ground Rods Do You Really Need?

Eighty percent of fence problems are grounding problems. Three rods, 6 ft, 10 ft apart.

Read it →

FAQ

The arithmetic questions

How much electric fence wire do I need for 1 acre?: A square acre is about 835 ft around. At three strands that's 2,505 ft of conductor, or 2,756 ft once you add 10% for corners, dips and terminations.
How many paddocks do I need for rotational grazing?: Rest days divided by grazing days, plus one for the paddock they're standing in. Thirty days of rest with three-day moves gives eleven paddocks; five-day moves give seven.
How many strands for horses, goats, cattle or deer?: Horses: three permanent, two seasonal, one interior. Goats and sheep: five, four, two. Cattle: two, two, one. Deer: three, at roughly 18, 34 and 50 inches. The perimeter counts for goats and cattle are manufacturer species guidance rather than extension guidance.
How much polywire for 5 acres?: A square five acres is about 1,867 ft around, so each cross-fence spans roughly 467 ft. If you own two reels and move them, that's about 1,030 ft of line out at once — one 1,640 ft roll covers it.
How many ground rods does an electric fence need?: Three at minimum: galvanized, 6 ft deep, 10 ft or more apart, for energizers up to 15 joules. Five up to 25 joules, seven up to 35.
What size energizer do I need?: Roughly one output joule per mile of total fence, doubled if grass and brush will touch the line. Size it low and the far corner is where you'll find out.

Good fences let you sleep.

How much fence do you need?

Your list

Everything else your fence needs

Every number on this page comes from one of these.

Geometry

Conductor

Hardware

Power and grounding

Paddocks

The same table the rotational grazing guide prints

Read this before you build

The Complete Beginner Setup Guide

The 1–5 Acre Rotational Grazing Starter Plan

How Many Ground Rods Do You Really Need?

The arithmetic questions

Your list

Everything else your fence needs