Stocking Rate Calculator
Calculate how many animals your pasture can carry for a grazing season from forage production and AUM math.
Loading calculator…
What this tool does
Calculate how many animals your pasture can carry for a grazing season from forage production and AUM math. The 50% default utilization is the classic 'take half, leave half' rule that keeps root reserves and ground cover. Production figures should come from local extension data or clipped plots for your land and year — drought years produce far less, and carrying last year's herd on this year's forage is the classic overgrazing trap.
How to use the Stocking Rate Calculator
- Enter or select forage production (lb dry matter per acre).
- Enter or select utilization rate (%).
- Enter or select pasture size (acres).
- Enter or select average animal weight in lb.
- Enter or select grazing season length (months).
- Read the calculated result; change any measurement to compare alternatives.
Formula
available forage = production × utilization × acres; one AUM (animal unit month) = 780 lb of dry matter for a 1,000 lb animal unit; animal-months supported = available forage ÷ (780 × animal weight ÷ 1,000); head for the season = animal-months ÷ season months — the standard extension AUM method
- forage
- Forage production (lb dry matter per acre)
- util
- Utilization rate (%)
- acres
- Pasture size (acres)
- weight
- Average animal weight (lb, before metric conversion)
- months
- Grazing season length (months)
The 50% default utilization is the classic 'take half, leave half' rule that keeps root reserves and ground cover. Production figures should come from local extension data or clipped plots for your land and year — drought years produce far less, and carrying last year's herd on this year's forage is the classic overgrazing trap.
Worked example
For stocking rate calculator, the following measurements illustrate the exact method: Forage production (lb dry matter per acre): 2000; Utilization rate (%): 50; Pasture size (acres): 100; Average animal weight: 1000; Grazing season length (months): 6.
Inputs
- Forage production (lb dry matter per acre)2000
- Utilization rate (%)50
- Pasture size (acres)100
- Average animal weight1000 lb
- Grazing season length (months)6
Result
- Animals supported for the season21.37
- Total AUMs available128.21
- Animal-months for your animals' size128.21
- Available forage (lb dry matter)100,000
- Acres per animal for the season4.68
Results explained
- Animals supported for the season
- Animals supported for the season from the formula above. The 50% default utilization is the classic 'take half, leave half' rule that keeps root reserves and ground cover. Production figures should come from local extension data or clipped plots for your land and year — drought years produce far less, and carrying last year's herd on this year's forage is the classic overgrazing trap.
- Total AUMs available
- Total AUMs available from the formula above. The 50% default utilization is the classic 'take half, leave half' rule that keeps root reserves and ground cover. Production figures should come from local extension data or clipped plots for your land and year — drought years produce far less, and carrying last year's herd on this year's forage is the classic overgrazing trap.
- Animal-months for your animals' size
- Animal-months for your animals' size from the formula above. The 50% default utilization is the classic 'take half, leave half' rule that keeps root reserves and ground cover. Production figures should come from local extension data or clipped plots for your land and year — drought years produce far less, and carrying last year's herd on this year's forage is the classic overgrazing trap.
- Available forage (lb dry matter)
- Available forage (lb dry matter) from the formula above. The 50% default utilization is the classic 'take half, leave half' rule that keeps root reserves and ground cover. Production figures should come from local extension data or clipped plots for your land and year — drought years produce far less, and carrying last year's herd on this year's forage is the classic overgrazing trap.
- Acres per animal for the season
- Acres per animal for the season from the formula above. The 50% default utilization is the classic 'take half, leave half' rule that keeps root reserves and ground cover. Production figures should come from local extension data or clipped plots for your land and year — drought years produce far less, and carrying last year's herd on this year's forage is the classic overgrazing trap.
Frequently asked questions
An animal unit month: the forage a 1,000 lb cow (with or without a calf, by local convention) eats in a month — standardized at about 780 lb of dry matter, from a daily intake near 26 lb. Bigger animals count as more than one AU in proportion to weight.
There is no universal number — it falls straight out of forage production. Productive pasture making 4,000 lb/acre at 50% use carries roughly 2.5 AUMs per acre for the season; dry rangeland making 800 lb/acre carries about half an AUM. This calculator does that math with your figures.
Plants need leaf area left to regrow and roots need reserves; grazing beyond ~50% of current-year growth weakens the stand and next year's production. The unused half also covers trampling, wildlife and drought insurance.
Yes — intake scales with body size. A 1,300 lb cow eats about 30% more than the 1,000 lb standard animal, so the same pasture supports proportionally fewer of her for the season.
Treat it as the ceiling for an average year. Prudent managers stock at 70–80% of the estimate or keep a destocking plan, because forage production in a drought year can halve while animal demand doesn't.