Pasture stocking rate calculator
Enter the pasture area, how much forage dry matter it holds and the share you plan to graze, then the animal weight, its daily intake and the length of the grazing period. The calculator gives how many animals the pasture carries and the stocking rate. The defaults are rules of thumb: change them to your own forage measurements.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Enter the pasture area and the forage dry matter it holds per acre or hectare.
- Set the utilisation, the average animal weight and the daily intake as a share of body weight.
- Enter the grazing period and read how many animals the pasture supports.
How it works
- usable forage = area × forage dry matter × utilisation;
- intake per animal = weight × intake %;
- animal-days = usable forage ÷ intake per animal;
- animals = animal-days ÷ days, rounded down.
The stocking rate is animals ÷ area, and animal units are that rate × weight ÷ 1,000 lb.
Example
25 acres with 2,200 lb of dry matter per acre, 50% utilisation, 1,200 lb cows eating 2.5% of their weight, 30 days:
- usable forage: 25 × 2,200 × 0.5 = 27,500 lb;
- intake: 1,200 × 0.025 = 30 lb per cow a day;
- animal-days: 27,500 ÷ 30 = 916.7 (shown as 916 whole days);
- cows for 30 days: 916.7 ÷ 30 = 30.6, so 30 cows, or 1.22 head (1.47 animal units) per acre.
Tips and common mistakes
- Use dry matter, not fresh weight: fresh grass is mostly water.
- Forage grows during the season. For long periods, plan with the forage you expect, not only what is standing now.
- Watch the pasture rather than the calendar and move animals when the residual height you want is reached.
Frequently asked questions
What utilisation should I use?
It is the share of the standing forage the animals actually eat, with the rest left for regrowth, trampled or wasted. “Take half, leave half” (50%) is a common rule of thumb for rotational grazing; set continuous grazing lower.
How much does a cow eat per day?
A common rule of thumb is about 2.5% of body weight in dry matter, so a 1,200 lb cow eats about 30 lb of dry matter a day. Lactating animals and high-quality forage push it up; poor forage pulls it down.
What is an animal unit?
A reference animal: a 1,000 lb (453.6 kg) cow, as used in US range management. The calculator divides the animal weight by 1,000 lb, so a 1,200 lb cow counts as 1.2 animal units.
How do I measure forage dry matter?
Clip the forage in a few small frames of known area, dry it and weigh it, or use a rising plate meter or grazing stick calibrated for your pasture. The default values are only examples.