Animal Unit Equivalent Calculator
Turn a mixed herd of cows, pairs, bulls, heifers and horses into one grazing demand number.
Your numbers
Total animal units in this herd
111 animal units
- Total AUMs for the period
- 775 AUM
- Dry matter required
- 302 tons DM
- Head counted
- 75 head
- Cow-calf pairs account for 84% of the total grazing demand.
- Convention: animal units scale linearly with body weight (weight ÷ 1,000 lb), the same convention used in state extension AUE tables and across every Agrilot grazing tool. Energy-based intake models such as NASEM scale by metabolic weight instead, and will differ modestly for herds well above or below a 1,000 lb mature weight.
- Federal grazing permits may specify their own AUM figure and their own class values. If you are budgeting a BLM or Forest Service allotment, use the numbers on your permit rather than these defaults.
- Bulls are usually turned out for a defined breeding season only — count their months separately if they leave the herd.
Show the math
- Cow-calf pairs60 head × 1.55 AU = 93.00 AU
- Mature bulls3 head × 1.90 AU = 5.70 AU
- Replacement heifers12 head × 1.00 AU = 12.00 AU
- Total animal units110.70 AU
- Animal unit months110.70 AU × 7.0 months = 774.9 AUM
- Forage required774.9 AUM × 780 lb DM = 604,422 lb DM
Assumptions this calculator used
Nothing here is hidden. Change any figure you have better local data for.
One 1,000 lb animal unit eating 26 lb of dry matter a day for 30 days — the most widely cited AUM figure. Some sources (older Forest Service and BLM range analysis handbooks) use a higher intake assumption, closer to 915 lb DM per AUM; adjust here if your agency or region specifies that figure. Source: USDA-NRCS National Range and Pasture Handbook.
lbRaise it toward 1.7 for big cows with older calves, drop toward 1.0 for a small-framed pair. Source: Kansas State & Oklahoma State Extension grazing guides.
AU
How to calculate animal unit equivalent
Pasture does not know the difference between a bull and three weaned calves — it only sees pounds of dry matter disappearing. Animal unit equivalents put every class of livestock on the same scale so a mixed herd can be budgeted against one forage supply.
Total AU = Σ (head × AUE per class) · AUM = total AU × months grazed
Convention used here: animal units scale linearly with body weight — weight ÷ 1,000 lb, plus a premium for lactation and growth. That is the convention behind the state extension AUE tables most operations already work from, and it is applied identically across the Agrilot stocking rate, grazing days and paddock size calculators, so numbers carry between them. Energy-based intake models such as NASEM scale by metabolic weight instead and will differ modestly for herds well above or below a 1,000 lb mature weight.
Worked example
60 pairs at 1.55 AU is 93 AU. Three bulls at 1.9 AU adds 5.7 AU. Twelve replacement heifers at 1.0 AU adds 12. The herd totals 110.7 AU. Grazed for seven months that is 775 AUM, which at 780 lb of dry matter per AUM calls for about 302 tons of harvestable forage.
Common mistakes
- Counting a pair as 1.0 AU all season. True at branding, badly wrong by August when the calf is 550 lb and grazing hard.
- Forgetting the horses. Six head of saddle horses on the same grass is 7.5 AU — a real bite out of a small operation's budget.
- Using the 1,000 lb reference cow for real cows. The reference animal is a unit of measure, not a description of your herd.
- Mixing federal permit AUMs with nutritional AUMs. They serve different purposes and rarely agree.
Animal unit equivalent values by class and weight
Commonly used AUE values from state extension services, all on the same linear body-weight scale this calculator uses: AUE = body weight ÷ 1,000 lb, plus roughly 20-25% for lactation. The default 1.9 AU herd bull in the calculator is a 1,900 lb bull on that same scale. Where two sources differ, the higher value is the safer planning number.
| Class | Body weight | AUE | Daily DM intake |
|---|---|---|---|
| Reference animal unit (dry cow) | 1,000 lb | 1.00 | 26 lb |
| Dry mature cow | 1,200 lb | 1.20 | 31 lb |
| Dry mature cow | 1,400 lb | 1.40 | 36 lb |
| Lactating cow with calf | 1,100 lb cow | 1.35 | 35 lb |
| Lactating cow with calf | 1,300 lb cow | 1.55 | 40 lb |
| Lactating cow with calf | 1,500 lb cow | 1.75 | 46 lb |
| Mature bull | 1,800 lb | 1.80 | 47 lb |
| Mature bull | 2,000 lb | 2.00 | 52 lb |
| Bred replacement heifer | 900 lb | 1.00 | 26 lb |
| Yearling stocker | 600 lb | 0.60 | 16 lb |
| Yearling stocker | 750 lb | 0.75 | 20 lb |
| Weaned calf | 500 lb | 0.50 | 13 lb |
| Mature horse | 1,100 lb | 1.25 | 33 lb |
| Mature ewe with lambs | 150 lb | 0.20 | 5 lb |
| Mature doe (goat) with kids | 120 lb | 0.17 | 4.4 lb |
Calculators to run next
- Grazing Days CalculatorUse when the herd is already in the paddock and you need a move date.
- Forage Yield CalculatorRun this first — every other grazing number depends on pounds of dry matter per acre.
- Paddock Size CalculatorUse when you are subdividing ground and need acres per break and paddock count.
- Pasture Rest Period CalculatorUse when regrowth is falling short and the rotation needs to slow down.
- Acreage CalculatorUse when you need the acreage of an odd-shaped field before any forage math.
- Stocking Rate CalculatorStart here when the question is how many cows the whole place will run for a season.
Guides that use this calculator
- How Many Cows Per Acre: Working Out Stocking Rate HonestlyCows per acre is an output, not an input. Here is the dry matter arithmetic behind it, the utilization rate most people get wrong, and honest numbers by region.
Questions ranchers ask
What exactly is one animal unit?
One animal unit (AU) is a 1,000 lb beef cow, dry or with a calf under three months, consuming about 26 lb of dry matter a day — roughly 780 lb of dry matter over 30 days, which is one animal unit month (AUM). Every other class is expressed as a fraction or multiple of that cow.
How do I calculate the AUE of a class not on the list?
Divide the animal's body weight by 1,000 — this calculator uses that simple linear body-weight ratio, the convention most state extension services (e.g. Oklahoma State PSS-2871) use for AUE tables, rather than scaling by metabolic body weight (weight^0.75) as NASEM's more detailed intake models sometimes do. The two methods agree closely near 1,000 lb and diverge for very light or very heavy animals. On top of the weight ratio, add roughly 20% to 25% for lactation and a small premium for growing animals, which eat slightly more per pound of body weight than mature stock. A 1,500 lb lactating cow works out to about 1.8 AU; a 600 lb growing steer to about 0.6 AU.
Is a cow-calf pair one animal unit or more?
The classic definition puts a pair at 1.0 AU while the calf is very young, because the calf is living on milk the cow is already eating for. By the time the calf is four to seven months old it is grazing on its own account, and the pair is realistically 1.25 to 1.4 AU on a modern 1,300 lb cow. This calculator uses the pair total, not the cow alone.
What is the difference between an AU, an AUE and an AUM?
An AU is the reference animal. An AUE is the equivalent value assigned to a particular class of livestock relative to that reference. An AUM is one AU grazing for one month — it is a quantity of forage, about 780 lb of dry matter, not a headcount.
Do horses count as more than cattle?
Yes. A 1,100 lb saddle horse is usually rated 1.25 AU, and some western range agencies use 1.25 to 1.5. Horses graze closer to the ground, are more selective, and spend more hours grazing than cattle, so their grazing impact exceeds their body weight ratio.
Why do BLM and Forest Service permits use different AUE numbers?
Federal grazing permits assign standardized AUM values by class for administrative fairness, and those numbers are sometimes lower than nutritional reality — a cow-calf pair is one AUM on most federal permits regardless of cow size. Use permit values for billing and permit compliance, and this calculator's values for actual forage planning.
Should sheep and goats be included in the same AU math?
They can be. Five mature ewes or six mature does are conventionally rated at one animal unit. On brushy or weedy ground, though, small ruminants eat forage cattle would not touch, so total AU may overstate their competition with the cow herd.
How do I turn total animal units into acres?
Multiply your total AU by the number of months grazed to get AUMs, then divide your harvestable forage in pounds of dry matter by 780 lb per AUM. Our stocking rate calculator does both steps and reports acres per cow directly.
Know your AU before you add a bull
A herd bull is nearly two animal units of grazing demand for the whole season. If you are shopping sires, Agrilot lists registered Angus bulls with full EPD profiles, mature weight data and an independent condition report, so the grazing cost buys you the genetics you actually intended.