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Grazing Stocking Rate Calculator

Work out how many animals your pasture can support for a given grazing period, using the real Animal Unit Month (AUM) method published across multiple US university extension range-science programs.

Pasture supplies19.2 AUM
Your herd needs90.0 AUM
Max animals for this period3

How to measure your inputs

  • Forage production: from a clip-and-weigh sample, or a local extension office's regional pasture productivity estimate.
  • Utilization rate: how much of that standing forage you plan to actually graze — "take half, leave half" (50%) is the standard sustainable default.

Methodology

AUM method: available AUM = (forage lb/acre × acres × utilization rate) ÷ 780 lb (the standard AUM definition). AUM demand = animal count × Animal Unit Equivalent × grazing months. Both figures and the AUM definition itself are published consistently across multiple university extension range-science programs.

The Animal Unit Month method, and why "take half, leave half" matters

What an Animal Unit Month actually represents

One AUM is the amount of dry forage a standard 1,000lb cow-calf pair eats in a month (≈780 lb) — a standardized unit published consistently across US university extension services (Montana State, Oklahoma State, University of Wyoming among others) that lets you compare forage demand across completely different animal types and herd sizes on the same scale.

Why you can’t graze 100% of standing forage

Grazing every last bit of standing forage damages root reserves and slows pasture recovery, reducing future production — the well-established "take half, leave half" principle in range management recommends leaving roughly 50% of forage ungrazed under normal conditions, which is why this calculator applies a utilization rate rather than assuming all forage production is usable.

Why different animals count differently toward the same pasture

A horse eats meaningfully more than a standard cow; a sheep or goat eats much less — the Animal Unit Equivalent (AUE) scales each species’ real forage demand relative to the 1,000lb-cow baseline, so a mixed herd’s total demand can be added together on one consistent scale.

Frequently asked questions

What is an Animal Unit Month (AUM)?

The amount of dry forage (about 780 lb) that a standard 1,000lb cow with an unweaned calf eats in one month — a standardized unit published by multiple US university extension range-science programs, used to compare forage demand across different animal types.

Why can’t I graze all the forage my pasture produces?

Grazing 100% of standing forage damages plant root reserves and slows regrowth, reducing future production — the standard "take half, leave half" practice leaves roughly 50% of forage ungrazed to protect long-term pasture health, which is why this calculator applies a utilization rate rather than counting all forage as usable.

How do I estimate my pasture’s forage production?

A clip-and-weigh sample (cutting and weighing forage from a known small area, then scaling up) gives a direct measurement; your local extension office may also publish typical forage production estimates for your region and pasture type as a starting reference.

Can I mix different animal types in one calculation?

This calculator handles one animal type at a time — for a mixed herd, calculate AUM demand for each species separately using its own Animal Unit Equivalent, then add the totals together and compare against your pasture’s available AUM.