Pasture Stocking Rate Calculator

Determine pasture carrying capacity, head counts, and Animal Unit Months (AUM) while preserving root reserves.

Pasture Area (Acres)

Estimated Forage Yield

Animal Class / Species

Grazing Period (Days)

Harvest Efficiency (Take-Half-Leave-Half)

Sustainable Carrying Capacity

3.7 Head

22.4 Animal Unit Months (AUM)

Usable Forage 17,500 lbs Dry matter harvested

Acres per Animal 5.4 Acres For 180 grazing days

Take Half, Leave Half Rule Never graze cool-season pasture below 3 to 4 inches of residual stubble. Grazing into the bottom 3 inches burns plant root energy reserves and allows weed seeds to germinate.

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How Animal Unit Months (AUM) Are Calculated

One Animal Unit (AU) is defined by the USDA and NRCS as a 1,000 lb mature beef cow with or without a nursing calf up to 6 months old. An Animal Unit consumes approximately 26.6 lbs of forage dry matter per day (800 lbs dry matter per month = 1 AUM).

Total Forage = Acres × Dry Matter Yield (lb/ac)
Usable Forage = Total Forage × Harvest Efficiency %
Total AUM = Usable Forage / 780 lbs per AUM
Head Capacity = Total AUM / (Grazing Months × AU Equivalent)

Frequently Asked Questions

Why is harvest efficiency only 25% to 35%?

Half of the plant must be left behind (50%) to preserve photosynthesis and root reserves. Of the remaining 50%, animals waste, trample, and defecate on roughly 15% to 25%, leaving 25% to 35% actually consumed.

How many sheep or goats equal 1 cow?

Five mature sheep or goats (weighing 140 to 160 lbs each with an AU factor of 0.20) equal 1 standard Animal Unit.

How does rotational grazing increase carrying capacity?

Dividing pastures into paddocks gives resting plants 21 to 35 days to regenerate without being re-grazed, boosting forage production and harvest efficiency by 30% to 50%.