How to use the pasture carrying capacity calculator
- Enter the size of the pasture in acres.
- Enter the acres each animal needs. The 2 shown is an example, so use a figure that fits your rain, soil, grass and animal.
- Open More options to remove land that cannot be grazed, and to enter the size of your herd.
- Read the number of animals the pasture supports, or the acres your herd needs.
Formula
grazable acres = pasture acres x (1 - share that cannot be grazed / 100)
animals supported = grazable acres / acres per animal, rounded down
acres for a herd = animals x acres per animal
The count is rounded down because a partial animal cannot be stocked. The exact figure before rounding is shown so you can see how close you are to the next whole animal.
20 acres at 2 acres per animal
Twenty acres at 2 acres per cow support 20 / 2 = 10 cows. If 10 percent of the land is a pond and brush that cannot be grazed, the grazable land is 18 acres and the pasture supports 9.
A 37 acre pasture with 25 percent unusable has 27.75 acres, and at 1.5 acres per animal the exact figure is 18.5, so it supports 18. A herd of 12 animals at 2 acres each needs 24 acres, which is 2 animals more than the 20 acre pasture supports.
Why the acres per animal is yours to set
No single number fits every farm. Rainfall, soil, the kind of grass, the season, the size of the animal and how you rotate the herd all change how much land each animal needs. Dry years can cut the carrying capacity sharply.
For a figure that suits your area, ask a local extension office or a grazing specialist, or use your own records of how many animals the land fed in past seasons. This page then does the arithmetic for the numbers you trust.
Feed and land planning
If the pasture falls short, work out supplemental feed with the Hay Needs Calculator, plan seeding with the Grass Seed Calculator, and plan other planted areas with the Trees per Acre Calculator.
Assumptions and limits
- All animals are treated as equal, so different sizes and ages are not weighted.
- The acres per animal figure is one number for the whole year.
- Drought, rotation, supplemental feed and forage quality are not modeled.
- Nothing is uploaded. The arithmetic runs in your browser.
Frequently asked questions
How many cows can I keep on 20 acres?
At 2 acres per cow, 10. The right acres per animal depends on your land and climate, so replace the example with a figure that fits your area.
What is a stocking rate?
It is the number of animals on a given area of land, such as animals per acre. This page also shows the reverse, acres per animal, and the count the land supports.
How do I take out land that cannot be grazed?
Enter the share of the pasture covered by ponds, buildings, rock or dense brush in More options. The page subtracts it before dividing.
Why is the animal count rounded down?
You cannot stock part of an animal, and rounding up would put the pasture past the figure you chose. The exact number is shown beside the whole one.