Pasture Rotation Days Calculator

Pasture Rotation Days

Rotational grazing (also “managed intensive grazing” or “MiG”) moves livestock through small paddocks to maximize forage growth and minimize overgrazing.

The simple formula: Days per paddock = (Paddock area × Forage availability) / (Animals × Daily intake)

Animal forage demand (AUM = Animal Unit per Month, where 1 AU = 1,000 lb cow):

Forage production by pasture quality (annual):

Annual production is not what is standing there today

The table above is what an acre grows over a whole year. The dropdown in the calculator asks for something different and smaller: the dry matter standing in the paddock right now, on this pass. An improved cool-season pasture producing 5,500 lb a year does it across three or four grazing passes, so each pass finds roughly 2,500 lb of standing forage, not 5,500.

Getting these two confused is the most common error in paddock planning, and it always errs the same way: it doubles or triples how long you think a paddock will feed the herd, so animals stay too long and the grass never recovers. If you are measuring rather than guessing, a rising plate meter or even a ruler and a known-weight clipping will beat any table on this page.

Rangeland is the exception in the dropdown, because semi-arid range grows once or perhaps twice a year rather than continuously, so a single pass finds a much larger share of the annual total.

Paddock size formula: Paddock acres needed = (Animals × Days × Daily intake) / (Available forage lb DM/acre × Take rate)

Where take rate is 40-60% for sustainable grazing (leave at least 40% of plant for regrowth).

Rest period after grazing:

Why rotational grazing wins:

1. More forage per acre: 30-100% more grass production than continuous grazing
2. Soil health: Hoof action breaks crust, manure spreads evenly
3. Weed suppression: Heavy competition from grasses outcompetes weeds
4. Animal performance: Fresher feed = more weight gain or milk
5. Drought resilience: Diverse plants and rest periods build root reserves

Key management rules:

• Move animals before grass is grazed below 4 inches (cool-season) or 6 inches (warm-season)
• Rest period > grazing period: typically 25-50 days rest, 1-3 days grazing
• Start with longer paddocks, divide as you learn forage / animal pace
• Watch for poison plants that grow when grass is overgrazed (jimsonweed, lupines)
• Provide water in every paddock: single-source water doubles labor and stresses cattle

Tools: polywire fence + step-in posts + portable energizer = subdivide a 5-acre pasture into 10 paddocks in 30 minutes.