Pasture Stocking Rate Calculator

What is an Animal Unit?

An Animal Unit (AU) is a planning yardstick: a 1,000-lb animal eating about 26 lb of dry matter per day (USDA/NRCS). Other stock convert to AU equivalents — a cow with calf is 1 AU, a horse 1.25, a sheep 0.2, and a goat 0.17. Thinking in AU lets you compare mixed herds on the same forage budget.

The math, step by step

Start with annual forage production for your quality class: good 3,000, average 2,000, or poor 1,000 lb dry matter per acre per year. Multiply by utilization (50% here — “take half, leave half”) to get usable forage. Multiply by acres for the season’s forage bank.

Worked example locked to our data: 5 acres of average pasture, 6-month season, sheep. Usable forage = 5 × 2000 × 0.5 = 5,000 lb. Season days = round(6 × 30.5) = 183. One sheep needs 0.2 × 26 × 183 ≈ 951.6 lb DM. Floor(5,000 / 951.6) = 5 head (exact ≈ 5.25). You cannot stock a fraction of a ewe, so the calculator floors the count.

Eyeballing forage quality

Good pasture is dense, diverse, and recovers quickly after a graze. Average stands have thin spots and shorter rest. Poor pasture is weedy, bare, or continuously grazed to dust. If you hay the same fields, bale weights are a reality check on the production class you pick. Drought years can cut yield 30–50% — restock downward before animals lose condition. When in doubt, pick the poorer class for the first season and raise stocking only after you see leftover forage and steady body condition scores.

Continuous vs rotational grazing

This tool uses a fixed 50% utilization. Well-managed rotation often harvests forage more evenly and protects residual cover; continuous grazing on the same paddock usually forces you toward the poor class over time. Rotation does not magically create feed that never grew — it helps you use what grew without wrecking the sward.

Mixed herds and parasites

Sheep and goats as browsers/grazers alongside cattle can improve plant use and break some parasite cycles, but AU math still applies: add the AU of each group before you claim the pasture is “empty.” Pair stocking results with the goat hay calculator for winter when grass is done.

Walk the pasture mid-season. If residual forage is shorter than you planned, destock or shorten the grazing window — the calculator’s floor is a starting point, not a dare. Water and shade often limit herds before forage does; use the rainwater and livestock water calculator so tanks keep up with the head count you just set.

Horses need careful attention: at 1.25 AU they eat like more than a cow-calf pair on paper, and selective grazing creates lawns and weeds if they stay in one paddock too long. Move them, or accept that “horse pasture” often grades toward the poor production class without rest.

Frequently asked questions