How many animals can your pasture carry?

What the number means

A stocking rate is how many animals a piece of land can feed for how long without being worn down. Too few animals leave forage unused; too many strip the plants, and Nebraska Extension warns that chronic overgrazing can irreversibly damage the pasture because regrowth then has to draw on energy stored in the roots. The animal unit system matches forage demand to forage supply by turning every animal into a number of 1,000-pound cow equivalents and every month of grazing into pounds of forage.

The method, step by step

1. Animal units: head × average weight ÷ 1,000 (each 100 pounds is 0.1 AUE). 2. Demand: animal units × days × forage per animal unit per day, 26 pounds by default, which is 780 pounds per animal unit month. 3. Supply: acres × forage yield in pounds per acre × harvest efficiency. The calculator solves the balance for the unknown you pick: head = supply ÷ (days × 26) ÷ (weight ÷ 1,000); acres = demand ÷ (yield × harvest efficiency); days = supply ÷ (animal units × 26). It also prints the animal unit months, AUM = animal units × days ÷ 30, and the acres per animal unit.

Worked example

A 40-acre pasture grows 3,000 pounds of forage an acre over the season. At 25 percent harvest efficiency 750 pounds an acre count, 30,000 pounds for the whole pasture. A 1,000-pound cow on it for 180 days needs 26 × 180 = 4,680 pounds, so the pasture supports 6.4 cows, which is 6.2 acres per animal unit. Run the same pasture at 50 percent and the answer doubles to 12.8, which is the take half, leave half rule applied to the total, before any loss to trampling. Reversing the question, ten 1,000-pound cows for 180 days need 62.4 acres, and ten cows on 10 acres would eat through the forage in 29 days.

Common mistakes and limits

First, mixing up kinds of pounds. Nebraska Extension measures forage in air-dried pounds, which is about 90 percent dry matter, and the daily 26 pounds goes with it. If you clip fresh grass and weigh it wet you will overstate the supply; if another source quotes dry matter, check which pounds it uses. Second, treating the total as the harvest: Nebraska notes that the total forage on a pasture does not equal what can be sustainably harvested, and that only about half of the forage removed is eaten, so a harvest efficiency near 100 percent will overgraze the land. Third, treating the animal unit as exact: the actual intake varies with breed, age, pregnancy, the digestibility of the diet and the season. Fourth, forgetting diet differences. Sheep and goats eat more forbs and browse than cattle, so a clipping that counts only grass undercounts their food. The result is a first estimate; Nebraska advises monitoring the pasture and adjusting the number of animals or the days.

A word on the NRCS figures

The National Range and Pasture Handbook of the USDA Natural Resources Conservation Service is the standard government reference for animal units. We could not open it while writing this page, so the calculator rests on the Nebraska Extension guide, which we did read in full, and exposes the daily forage as a field. Other sources count an animal unit month in oven-dried pounds or at different weights, and the field lets you follow whichever your local office uses.

What is an animal unit?

An animal unit equivalent (AUE) is one 1,000-pound beef animal, and each additional 100 pounds of body weight adds 0.1, according to Nebraska Extension. A 1,200-pound cow counts as 1.2, five 200-pound ewes as 1, and ten 100-pound sheep, five 50-pound goats and two 1,000-pound steers grazing together as 3.25. The system began with beef cattle, but Nebraska applies the same weight-based values to sheep and goats, and the calculator does so for any animal whose weight you enter, including horses.

What is an AUM?

An animal unit month (AUM) is the forage needed to keep one animal unit for one month, 30 days. Nebraska Extension puts a good general estimate at 780 pounds of air-dried forage per AUM, which is 26 pounds a day, and notes that the real amount varies with breed, forage type, season and environment. Some sources count dry matter instead of air-dried forage, which is why the daily forage per animal unit is a field in the calculator: 26 pounds is the default.

What is harvest efficiency, and why 25 percent?

Harvest efficiency (HE) is the share of the forage that stock actually eat. Nebraska Extension recommends stocking no more than about half of the estimated total forage (take half, leave half), and notes that as little as half of the forage removed is actually eaten, with the rest trampled, soiled or taken by wildlife and insects, so about 25 percent of the total is a sensible plan for a pasture you want to keep. It adds that HE is lowest under continuous grazing and highest in management-intensive grazing, and that a starting HE of 25 percent is usually reasonable.

How do I measure how much forage I have per acre?

Nebraska Extension describes clipping: toss a small hoop or square of known area, such as 2 × 2 feet (4 square feet), at random, clip all the forage in it at ground level, repeat in several places including low and high ground, air-dry the sample for a week in a warm, dry place (air-dried forage is about 90 percent dry matter), weigh it, and divide the weight by the total area. Multiply pounds per square foot by 43,560 square feet in an acre to get pounds per acre. Sample your own land: published yields for a vegetation zone are only a quick reference.

How many acres per cow do I need?

It depends on yield and on how many days the cows graze there. With 3,000 pounds of forage per acre, 25 percent harvest efficiency, 26 pounds per animal unit a day and 180 days, one 1,000-pound cow needs 6.2 acres. If the grazing season is 90 days, the acres halve. There is no number that works everywhere; a thin pasture needs many more acres and a well-managed one fewer.

Do sheep and goats count the same as cattle?

By weight, yes: a 200-pound ewe is 0.2 AUE and a 150-pound doe 0.15. But Nebraska Extension points out that their diets differ. Sheep choose about 60 percent grasses, 30 percent forbs and 10 percent browse, goats about 20 percent grasses, 20 percent forbs and 60 percent browse, so you should count the plants they actually eat when you clip your sample.

Sources: University of Nebraska–Lincoln Extension, NebGuide G2344 “Introduction to Animal Unit (AU) Concepts for Production of Sheep and Goats” (M. Most and D. Yates, May 2022; animal unit equivalent, AUM of 780 pounds, forage clipping method, take half leave half, harvest efficiency of 25 percent), read October 28, 2026. The USDA NRCS National Range and Pasture Handbook could not be opened. Arithmetic on those figures is ours. Related: hay needed calculator for the winter, horse weight calculator, acreage calculator, fence calculator and pond calculator. How we check our calculators.