Calculate carrying capacity based on forage yield and grazing duration.
Clip-and-weigh estimate or stick method.
Usually 50% ("Take half, leave half").
Dry: 2.5-3% | Lactating: 3.5-4%
Maximum Herd Size: 0 Sheep
Total Available Forage (Usable):0 lbs
Daily Intake per Sheep:0 lbs
Total Forage per Sheep (Full Duration):0 lbs
Stocking Density (Sheep/Acre):0
Understanding Sheep Stocking Rates
Properly calculating your sheep stocking rate is the cornerstone of sustainable pasture management. Overstocking leads to soil degradation, weed proliferation, and poor animal performance, while understocking results in wasted forage and lower profitability. This calculator uses the standard forage budget method to determine how many sheep your land can support for a specific period.
Key Metrics Explained
Forage Yield (lbs/acre): This is the total dry matter available on your pasture. It varies significantly by region, season, and rainfall. You can estimate this using a grazing stick or the "clip and weigh" method.
Utilization Rate (%): You cannot let sheep eat 100% of the grass. The roots require leaf area to regenerate. The standard rule of thumb is "take half, leave half" (50% utilization), though this may be lower (30-40%) in arid environments or higher (60-70%) in intensive rotational grazing systems.
Daily Intake (% of Body Weight): A sheep's Dry Matter Intake (DMI) depends on its physiological state.
Dry Ewes: Typically consume 2.0% to 2.5% of body weight.
Late Gestation: Increases to 3.0%.
Lactating Ewes: High demand, consuming 3.5% to 4.5% of body weight.
The Calculation Formula
We calculate the stocking rate using the following steps:
Calculate Total Usable Forage:(Acres × Yield per Acre) × (Utilization Rate ÷ 100)
If you practice rotational grazing, adjust the "Grazing Duration" input to reflect the number of days the flock spends in a single paddock before moving. This allows you to size your paddocks correctly or adjust the herd size to match the rotation schedule.
function calculateSheepStocking() {
// 1. Get input values
var pastureSize = parseFloat(document.getElementById('pastureSize').value);
var forageYield = parseFloat(document.getElementById('forageYield').value);
var utilizationRate = parseFloat(document.getElementById('utilizationRate').value);
var sheepWeight = parseFloat(document.getElementById('sheepWeight').value);
var intakeRate = parseFloat(document.getElementById('intakeRate').value);
var grazingDays = parseFloat(document.getElementById('grazingDays').value);
// 2. Validate inputs
if (isNaN(pastureSize) || isNaN(forageYield) || isNaN(utilizationRate) ||
isNaN(sheepWeight) || isNaN(intakeRate) || isNaN(grazingDays)) {
alert("Please fill in all fields with valid numbers.");
return;
}
if (grazingDays <= 0 || sheepWeight <= 0) {
alert("Days and Weight must be greater than zero.");
return;
}
// 3. Perform Calculations
// A. Calculate Total Available Dry Matter (lbs)
// Formula: Acres * lbs/acre
var totalBiomass = pastureSize * forageYield;
// B. Calculate Usable Forage based on Utilization Rate
// Formula: Total Biomass * (Percentage / 100)
var usableForage = totalBiomass * (utilizationRate / 100);
// C. Calculate Daily Intake per Sheep (lbs/day)
// Formula: Body Weight * (Intake % / 100)
var dailyIntakePerSheep = sheepWeight * (intakeRate / 100);
// D. Calculate Total Intake Required per Sheep for the Duration (lbs)
// Formula: Daily Intake * Days
var totalIntakePerSheep = dailyIntakePerSheep * grazingDays;
// E. Calculate Max Number of Sheep
// Formula: Usable Forage / Total Intake per Sheep
var maxSheep = Math.floor(usableForage / totalIntakePerSheep);
// F. Calculate Density (Sheep per Acre)
var density = (maxSheep / pastureSize).toFixed(1);
// 4. Update the Result Display
document.getElementById('resMaxSheep').innerHTML = maxSheep.toLocaleString();
document.getElementById('resTotalUsable').innerHTML = Math.round(usableForage).toLocaleString() + " lbs";
document.getElementById('resDailyIntake').innerHTML = dailyIntakePerSheep.toFixed(1) + " lbs";
document.getElementById('resTotalPerSheep').innerHTML = Math.round(totalIntakePerSheep).toLocaleString() + " lbs";
document.getElementById('resDensity').innerHTML = density + " head/acre";
// Show results container
document.getElementById('ssrResults').style.display = 'block';
}