Pasture Stocking Rate Animal Unit Month Calculator
Calculate pasture stocking rate in animal unit months from forage production, pasture acres and animal demand, for sustainable grazing.
How This Calculation Works
An animal unit month is the forage one 1,000-pound cow with a calf consumes in a month, about 780 pounds of dry matter. Stocking rate equals usable forage production divided by the animal unit month requirement. A pasture producing 2,000 pounds of usable forage per acre supports about 2.5 animal unit months per acre.
Field Calibration & Rate Reference Chart
| Area | Square feet | Acres | Square field side |
|---|---|---|---|
| 1,000 sq ft | 1,000 | 0.023 | 32 ft |
| 5,000 sq ft | 5,000 | 0.115 | 71 ft |
| 10,000 sq ft | 10,000 | 0.230 | 100 ft |
| 0.25 acre | 10,890 | 0.250 | 104 ft |
| 0.5 acre | 21,780 | 0.500 | 148 ft |
| 1 acre | 43,560 | 1.000 | 209 ft |
| 5 acres | 217,800 | 5.000 | 467 ft |
| 10 acres | 435,600 | 10.000 | 660 ft |
| 40 acres | 1,742,400 | 40.000 | 1,320 ft |
| 100 acres | 4,356,000 | 100.000 | 2,087 ft |
Common Questions
What is an animal unit month?
An animal unit month is the forage one 1,000-pound cow with a calf consumes in a month, about 780 pounds of dry matter. It is the standard unit for comparing pasture carrying capacity. Different classes of livestock are converted to animal units.
How do I calculate stocking rate?
Divide usable forage production by the animal unit month requirement. A pasture producing 2,000 pounds of usable forage per acre supports about 2.5 animal unit months per acre. Use measured production, not a guess.
How much forage should I leave as residue?
Leave at least half the season's growth as residue to protect the soil and keep plants vigorous. Grazing below that weakens the stand and invites weeds. Rotational grazing helps manage residue.
Does stocking rate change with rainfall?
Yes, forage production tracks rainfall, so a dry year cuts carrying capacity sharply. Adjust the rate each year and have a plan to destock early in a drought. Overstocking in a dry year damages the pasture for years.