Estimate how many cattle your pasture can support based on forage production, grazing efficiency, and herd weight — get head count, acres per head, and total grazing capacity.
Quick Facts
Animal Unit (AU)
Reference animal = 1,000 lb cow
Heavier or lighter cattle scale proportionally — a 1,200 lb cow is 1.2 AU.
Daily forage intake
≈26 lbs dry matter per AU per day
About 2.6% of body weight — the standard NRCS/extension intake rate.
Grazing efficiency
Continuous grazing: ~25% · rotational: ~40-50%
The rest of what grows is trampled, fouled, or left uneaten.
Results
Calculated
Cattle Per Acre
—
Head supported per acre
Recommended Herd Size
—
Head for the full grazing period
Acres Needed Per Head
—
Stocking density (acres/head)
Grazing Capacity
—
Total Animal Unit Months (AUM)
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Enter your pasture, forage, and herd details, then press Calculate.
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How this calculator works
This tool applies the standard stocking-rate method used by USDA NRCS and university extension programs to estimate how many cattle a pasture can carry. It converts your pasture's forage production into a herd size by comparing usable forage supply against the forage a herd actually eats over the grazing period.
The formula
Usable forage (lbs) = Forage Production (lbs/acre) × Pasture Size (acres) × Grazing Efficiency (%). Each Animal Unit (AU, a 1,000-lb cow) eats about 26 lbs of forage dry matter per day, so a herd's total demand per head over the grazing period is 26 × (Average Weight ÷ 1,000) × Grazing Days. Dividing usable forage by that per-head demand gives the number of head the pasture supports; dividing head by acres gives cattle per acre, and its inverse gives acres needed per head. Total grazing capacity is also expressed in Animal Unit Months (AUM), where 1 AUM = 26 lbs/day × 30 days ≈ 780 lbs of forage per AU.
Understanding the inputs
Pasture Size is the total grazable acreage. Forage Production is the usable dry-matter forage grown per acre over the period — check a soil or forage test, or a regional extension guide, for a realistic figure for your land. Grazing Efficiency reflects how much of that forage cattle actually consume versus trample or leave behind — roughly 25% for continuous season-long grazing, up to 40-50% with well-managed rotational grazing. Average Cattle Weight converts head count to Animal Units. Grazing Period is how many days the herd will graze this pasture.
Interpreting the results
Cattle Per Acre and Recommended Herd Size show how many animals the pasture supports for the full grazing period; treat these as an upper estimate and round down for a conservative stocking plan. Acres Needed Per Head is the inverse — useful for comparing against typical local stocking densities. Grazing Capacity (AUM) is the total forage supply expressed independent of any particular herd size, useful for planning multiple pastures or grazing periods.
Frequently Asked Questions
What is the formula for cattle per acre?
Usable forage (lbs) is found by multiplying forage production per acre by the number of acres and the grazing efficiency. Dividing that by the forage a herd needs for the grazing period gives the number of head the pasture supports; dividing head by acres gives cattle per acre. This is the standard stocking-rate method used by USDA NRCS and university extension offices.
How much forage does a cow eat per day?
The standard reference is 26 lbs of forage dry matter per day for one Animal Unit (AU), defined as a 1,000-lb cow — about 2.6% of body weight. A 1,200-lb cow equals 1.2 AU and eats roughly 31 lbs per day. This value is published by USDA NRCS and land-grant university extension programs.
Why isn't all the forage that grows available to cattle?
Grazing (harvest) efficiency accounts for forage that is trampled, fouled, left ungrazed, or lost to weathering. Continuous season-long grazing typically captures only 25 percent of what grows, while well-managed rotational grazing can reach 40 to 50 percent or more.
How many acres does one cow need?
It depends entirely on local forage production. Productive, well-watered pasture may support one cow on 1 to 3 acres, while arid rangeland can require 20 to 50 acres or more per cow. Enter your own forage yield and efficiency to get a figure specific to your land.