How do you calculate the number of paddocks needed?

The number of paddocks equals the rest period divided by the grazing period, plus one. The plus one ensures the herd has a fresh paddock to move into while every other paddock completes its rest. For a 30-day rest and 3-day grazing, you need 30 / 3 + 1 = 11 paddocks.

What is a rest period and why does it matter?

The rest period is how long a paddock recovers before being grazed again. It must be long enough for plants to regrow leaf area and rebuild root reserves. Too short and the pasture is overgrazed; too long and forage becomes mature and low quality. It varies with season and growth rate.

How long should the grazing period be?

Shorter is generally better for plant health. Keeping animals on a paddock one to three days prevents them from regrazing fresh regrowth before they move on. Longer grazing periods need more rest to compensate and can stress the most palatable plants.

How do animal units relate to stocking?

An animal unit (AU) is a standard 1,000-pound animal eating about 26 pounds of dry forage per day, roughly 3 percent of body weight. Converting your herd to animal-unit equivalents lets you compare forage demand against available pasture regardless of species or class.

What is the rotation cycle length?

The cycle length is how long it takes the herd to graze every paddock once and return to the first. It approximately equals the rest period plus one grazing period. Watching the cycle against pasture growth tells you when to speed up or slow down the rotation.

What is the Paddock Rotation Calculator?

Design rotational grazing systems by computing the number of paddocks, grazing days per paddock, and herd forage demand from rest period, herd size, and pasture area. Built for graziers planning strip, cell, and management-intensive grazing. It runs free in your browser on Gera Tools, with nothing uploaded.

Paddock Rotation Calculator

Name: Paddock Rotation Calculator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

A productive grazing rotation balances how long animals stay against how long pastures rest. This calculator converts your target rest period and grazing period into the number of paddocks you need and the length of the rotation cycle, with an optional stocking check from herd size and available forage.

How it works

The paddock count comes directly from the rest-to-graze ratio:

paddocks      = (rest period / grazing period) + 1
cycle length  ≈ rest period + grazing period
forage demand = animal units × 26 lb/day × grazing period   (optional)

The plus-one guarantees a fresh paddock is always ready while the rest of the cells finish recovering. The optional forage demand uses the standard animal-unit intake of about 26 pounds of dry matter per day.

Why the grazing period should be short

The grazing period is the number of days animals stay on a single paddock before moving on. Short grazing periods — typically one to three days — are central to management-intensive grazing for several reasons:

Preventing selective grazing. When animals stay too long, they regraze the most palatable regrowth while leaving less desirable plants. This progressively weakens the preferred species and allows weeds and rank species to dominate. Moving animals before they have a chance to regraze keeps all species grazed more uniformly.

Protecting root reserves. Plants mobilise carbohydrate reserves from roots to drive initial leaf regrowth after grazing. If animals regraze the new leaves before the plant has had time to replenish root stores, the plant weakens over time. Short grazing periods followed by adequate rest allow full recovery.

Maintaining animal performance. Animals on a fresh paddock consume the most nutritious forage first. After the first day or two, forage quality in the paddock declines as animals sort through what remains. Moving them onto fresh ground consistently exposes them to high-quality leafy material.

Setting the rest period by season

The correct rest period is not fixed — it is driven by how fast pasture grows, which varies with temperature, moisture, and season. Adjust the rotation speed dynamically:

Season / condition	Growth rate	Recommended adjustment
Spring flush	Fast	Shorten rest, add temporary paddocks
Summer stress (drought, heat)	Slow	Lengthen rest, reduce stocking rate
Autumn regrowth	Moderate	Standard rest period
Winter dormancy	Near zero	Very long rest or conserved forage

A rotation that works in April may be too fast in August. Watching residual height — the stubble height remaining after animals leave a paddock — is the most practical indicator: consistent low residuals mean the rotation is too slow (or stocking too high); high residuals with waste mean the rotation is too fast (or stocking too low).

Worked example

Setup: 30-day target rest period, 3-day grazing period, 50 animal units.

Paddocks = (30 / 3) + 1 = 11
Cycle length = 30 + 3 = 33 days
Forage demand per move = 50 AU × 26 lb/day × 3 days = 3,900 lb dry matter

Eleven paddocks on a 400-acre farm means roughly 36 acres per paddock. Before the rotation begins, calculate whether 36 acres of available forage at typical dry matter yield (for example, 1,500 to 2,000 lb per acre at 3 to 4 inches of available growth) actually meets the 3,900-pound demand. If not, the paddocks are too small and either stocking rate needs to come down or the grazing period needs to extend to allow more forage per move.

The plus-one explained

Without the extra paddock, there would be no fresh paddock available on the day the herd leaves the last cell in the sequence — they would have to wait for the first paddock to finish its rest. The plus-one creates a buffer so there is always a paddock at or past its minimum rest target when the herd needs to move.