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Pasture Stocking Rate Calculator for Cattle

Estimate how many cows your pasture can carry, and for how long, from your acres and how much grass it grows. It runs in your browser, is free, and needs no signup.

How the math works

1. Total forage = acres × pounds of dry matter grown per acre.
2. Harvest efficiency. Cattle eat only part of what grows; the rest is trampled, fouled, eaten by wildlife and insects, or left as cover so the grass recovers. Extension and NRCS planning guides use about 25% for continuous grazing, 25–30% for rotations with several pastures, and 30–35% for short-duration, high-intensity grazing. This is the "take half, leave half" rule with grazing losses taken out.
3. Animal unit month (AUM). One animal unit is a 1,000 lb cow, with or without a young calf. It eats about 26 lb of forage dry matter a day, or about 790 lb a month (26 × 30.4 days). Heavier cows count as more than one unit: a 1,200 lb cow is about 1.2 units.
4. Cows supported = available forage ÷ 790 ÷ (cow weight ÷ 1,000) ÷ months of grazing.

This is a starting estimate, not a grazing plan. Rainfall swings forage production a lot from year to year, so check your pastures through the season and adjust. Your county Extension agent or local NRCS office can help you set a stocking rate for your land, often at no charge.

Sources

• SDSU Extension: Setting the Stocking Rate (animal unit definition, 25% harvest efficiency, 30–35% under rotation)
• USDA NRCS: Estimating Initial Stocking Rates (harvest efficiency by grazing system, take half and leave half)
• Montana State University Extension: Animal Unit Month lease rates (1 AUM = 790 lb of forage)
• New Mexico State University: Is there enough grass? (balancing forage supply and demand)

Related: winter hay needs calculator · virtual fencing and grazing tools · grazing tools · free cattle record template

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