How to calculate a rotational grazing plan
- Choose a calculation mode. Choose whether to split available pasture, size paddocks from herd and forage, or estimate how long a known paddock will last.
- Enter the essentials. Enter the grazeable area or known paddock area, occupation time, recovery target, and grazing groups required by the selected mode.
- Check assumptions. Open Advanced forage assumptions to review measured forage, residual, harvest efficiency, reserve, shape, water location, and start date.
- Read the action plan. Use the plain-language plan first, then compare forage-demand and equal-share layouts, seasonal scenarios, and the first-cycle schedule.
- Monitor and adjust. Treat calendar recovery as a planning target and return only when plants are ready; adjust for residual, weather, animal performance, water, and ground conditions.
Input guidance and starting ranges
Measure pre-graze dry matter: clip several representative quadrats to the planned grazing height, dry the samples to constant weight, and scale the average to an acre or hectare. A calibrated grazing stick or rising plate meter is faster, but its mass-per-height relationship must match the local forage mix and conditions. See the UF/IFAS Extension forage-mass method.
Keep residual separate from harvest efficiency: residual is the material deliberately left after grazing; harvest efficiency is the fraction above that residual expected to be consumed. Combining them can accidentally count protected plant material as feed.
| Livestock class | Editable intake starting range | Source note |
|---|---|---|
| Beef cattle / stockers | 2โ3.5% of body weight as DM/day | Penn State Extension; class, forage, and growth change intake. |
| Lactating dairy cows | About 2.5โ4.3% at 20โ100 lb milk/day for large breeds | Penn State Extension; use actual ration intake when available. |
| Sheep and goats | 2โ4% of body weight as DM/day | University of Arkansas Extension. |
| Horses | 1.5โ2.5% of body weight total feed/day; 2% is a common target | University of Minnesota Extension; pasture intake is variable. |
| Growth condition | Example recovery window | Contingency reserve preset |
|---|---|---|
| Fast spring growth | 10โ14 days | 10% |
| Normal / moderate growth | 20โ30 days | 15% |
| Summer stress | 30โ35 days | 20% |
| Hot, dry / drought | 40โ60 days | 30% |
| Dormant or stockpiled | 45โ65 day slow-growth screen; manage from inventory where regrowth has stopped | 35% |
Recovery windows are adapted from Penn State Extension and the NRCS prescribed-grazing factsheet. Reserve percentages are conservative calculator allowances chosen by Starlight Tools, not extension prescriptions. Plant readiness overrides every calendar value.
| Move frequency | Example utilization / harvest efficiency |
|---|---|
| 1 day | 80% |
| 2โ3 days | 75% |
| 4 days | 70% |
| 5 days | 65% |
These utilization examples come from Penn State Extension and are starting points only. Local pasture structure, density, animal behavior, weather, and management can differ.
Formulas and assumptions
Combined daily herd demand = ฮฃ(group count ร average live weight ร intake %)
Usable forage = (pre-graze dry matter โ residual) ร harvest efficiency
Forage-demand paddock area = daily herd demand ร grazing days รท usable forage
Minimum paddocks = ceiling(recovery days รท grazing days + 1)
Required area after reserve = required forage area รท (1 โ reserve %)
Known-paddock grazing days = paddock area ร usable forage ร (1 โ forage reserve %) รท daily herd demand
The forage-allocation and paddock-count relationships follow Penn State Extension; dry-matter supply and demand are cross-checked against Oklahoma State University Extension. The whole-paddock ceiling is intentional. Dimensions assume a rectangle with the selected ratio. Water distance is straight-line geometry to the farthest corner; it does not account for lanes, slope, barriers, flow, storage, or trough capacity.
Loadable worked scenarios
US beef cattle โ adequate acreage
Inputs: 30 beef cows ร 1,200 lb ร 2.5% = 900 lb DM/day. Usable forage: (2,400 โ 1,200) ร 75% = 900 lb DM/acre. A 2-day allocation is 1,800 รท 900 = 2 acres. Recovery: ceiling(30 รท 2 + 1) = 16 paddocks, requiring 32 acres before reserve. Decision: the entered 40 acres leave 8 acres outside the forage-demand rotation.
Metric goats โ small-ruminant plan
Inputs: 80 goats ร 55 kg ร 3% = 132 kg DM/day. Usable forage: (2,500 โ 1,200) ร 70% = 910 kg DM/ha. A 2-day allocation is 264 รท 910 = 0.29 ha. Recovery: ceiling(28 รท 2 + 1) = 15 paddocks, requiring about 4.35 ha before reserve. Decision: use flexible subdivisions and retain the rest of the entered 18 ha as reserve or outside the active rotation.
Drought / forage shortage โ insufficient acreage
Inputs: 60 beef cows ร 1,200 lb ร 2.5% = 1,800 lb DM/day. Usable forage: (1,800 โ 1,200) ร 65% = 390 lb DM/acre. A 3-day allocation needs 5,400 รท 390 = 13.85 acres. Recovery: ceiling(50 รท 3 + 1) = 18 paddocks, requiring about 249.2 acres before a 30% reserve. Decision: 30 acres cannot support the entered plan; reduce demand, add feed or land, use a sacrifice area, or destock rather than shortening recovery without plant evidence.
Methodology and review
Starlight Robotics / Starlight Tools
31 July 2026
31 August 2026
No independent agronomist or grazing specialist review is claimed.
The editorial review checked formulas against the cited extension and NRCS relationships, tested unit conversions and representative examples, and separated source-derived ranges from Starlight Tools' own conservative reserve presets. Agricultural assumptions remain user inputs because appropriate values depend on the farm, forage, animals, and season.
Rotational grazing FAQ
How is rotational grazing paddock size calculated?
Herd dry-matter demand for the grazing period is divided by usable forage per acre or hectare. Usable forage is the difference between pre-graze mass and residual, multiplied by harvest efficiency.
How many paddocks are needed for rotational grazing?
Divide recovery days by grazing days, add one, and round up. Rounding up ensures the planned recovery time is met or exceeded.
How many acres per cow are needed for rotational grazing?
There is no universal acres-per-cow figure. Carrying capacity depends on measured forage production, usable forage, animal weight and intake, season, soils, and management; calculate from a local forage inventory rather than a national rule of thumb.
How long should cattle stay in one paddock?
Use the shortest practical occupation that fits labor and infrastructure. One to three days is a common planning range, but move earlier when the target residual is reached and do not let animals regraze fresh regrowth.
What is the difference between stocking rate and stock density?
Stocking rate relates animal demand to the whole grazing area over a season or period. Stock density is the animals or live weight present on one allocation at one moment; it can be high even when the season-long stocking rate is moderate.
Can paddocks be different sizes?
Yes. Size allocations to forage and terrain rather than forcing identical permanent fields. Temporary fence can make smaller or larger daily allocations while the equal-share result provides a useful layout check.
How do supplemental feed and mixed herds affect the calculation?
Add each grazing class as a separate herd row so dry-matter demand is combined. If supplement replaces pasture intake, lower the pasture-intake percentage only by a defensible ration estimate; do not subtract supplement pound-for-pound without nutrition guidance.
How should drought change the rotation?
Lengthen recovery, increase reserve, reduce demand, use stored feed or a sacrifice area, and destock early if the forage budget requires it. Plant readiness overrides the preset calendar.
Where should water and lanes go?
Place reliable water to limit walking and improve distribution, and route lanes on durable, well-drained ground without concentrating runoff. The calculator's straight-line water check is a screening estimate, not a hydraulic or farm-layout design.
Why are residual and harvest efficiency separate?
Residual is forage deliberately left to protect plants and meet management goals. Harvest efficiency accounts for forage above that residual that is trampled, fouled, rejected, or otherwise not eaten.
What dry-matter intake percentage should I use?
Use the editable preset only as a starting point. Species, class, body weight, production, forage quality, weather, and supplementation can materially change intake, so use ration records or qualified nutrition guidance when available.
Should I use pasture height or forage dry matter?
Use measured dry matter per acre or hectare when possible. Convert height only with a locally calibrated grazing stick, plate meter, or species-specific relationship.
Does paddock count stay fixed all season?
No. Growth changes with species, weather, soil moisture, fertility, and season. Skip ready paddocks, add temporary subdivisions, slow the rotation, or remove animals as monitoring requires.
Are pasture and herd inputs stored?
No. Calculations run locally in the browser, and this calculator does not send or store the values entered into the tool.