Use this calculator to determine the exact amount of seed required per acre based on your target plant population, thousand kernel weight (TKW), and expected field emergence. This ensures optimal crop density without wasting expensive seed.
Input Crop Details
The number of established plants you want per acre (e.g., 1,200,000 for wheat, 32,000 for corn).
Weight of 1,000 seeds in grams. Check your seed tag.
Percentage of seeds expected to germinate and survive (Germination % – Mortality).
Optional: Enter cost to calculate total expense.
Results
Recommended Seeding Rate:0.0 lbs/ac
Seeding Rate (Bushels/ac):0.0 bu/ac
Total Seed Required:0 lbs
Seeds per Sq. Foot:0 seeds/ft²
Estimated Cost Per Acre:$0.00
Total Project Cost:$0.00
Understanding the Seeding Rate Formula
Calculating the correct seeding rate is one of the most critical agronomic decisions a producer makes. Relying on "bushels per acre" often leads to inaccurate stands because seed size varies significantly between varieties and seed lots.
The Math Behind the Calculation
This calculator uses the industry-standard agronomic formula to convert your target plant population into a weight-based seeding rate. The core logic handles the physics of seed weight and biological survival rates.
Target Plant Population: The final number of viable plants you want in the field per acre. This depends on crop type, rainfall region, and planting date. For example, spring wheat might target 1,000,000 to 1,400,000 plants/acre, while corn might target 30,000 to 36,000 plants/acre.
Thousand Kernel Weight (TKW): This measures seed size in grams. Large seeds have a higher TKW, meaning you need more pounds of seed to get the same number of plants.
Small Wheat Seed: 30g TKW
Large Wheat Seed: 45g TKW
Expected Field Emergence: This is rarely 100%. It accounts for germination rate (from the seed tag) minus estimated mortality due to disease, insects, cold soil, or seeding depth issues. A typical range is 85% to 95%.
Example Calculation
Let's look at a realistic scenario for planting Wheat:
If you were simply planting at a flat "2 bushels per acre" (approx 120 lbs), you might be over-seeding and wasting money. Conversely, if your seed was very large (TKW 45g), 2 bushels might not result in enough plants.
function calculateSeedingRate() {
// Get inputs
var targetPop = parseFloat(document.getElementById('targetPopulation').value);
var tkw = parseFloat(document.getElementById('tkw').value);
var emergence = parseFloat(document.getElementById('emergenceRate').value);
var acres = parseFloat(document.getElementById('totalAcres').value);
var costPerLb = parseFloat(document.getElementById('costPerLb').value);
// Validation: Ensure we have the critical values to calculate rate
if (isNaN(targetPop) || isNaN(tkw) || isNaN(emergence) || emergence <= 0) {
// If inputs are missing, just clear results or show zero, prevent NaN display
document.getElementById('resultRateLb').innerHTML = "0.0 lbs/ac";
document.getElementById('resultRateBu').innerHTML = "0.0 bu/ac";
document.getElementById('resultTotalSeed').innerHTML = "0 lbs";
document.getElementById('resultSeedsSqFt').innerHTML = "0 seeds/ft²";
document.getElementById('resultCostPerAcre').innerHTML = "$0.00";
document.getElementById('resultTotalCost').innerHTML = "$0.00";
return;
}
// 1. Calculate Seeds Needed per Acre (accounting for survival)
// Formula: Target / (Emergence % / 100)
var seedsPerAcre = targetPop / (emergence / 100);
// 2. Calculate Weight in Grams per Acre
// Formula: SeedsPerAcre * (TKW / 1000)
var gramsPerAcre = seedsPerAcre * (tkw / 1000);
// 3. Convert Grams to Pounds (1 lb = 453.59237 grams)
var lbsPerAcre = gramsPerAcre / 453.59237;
// 4. Calculate Bushels per Acre (Standard Wheat Bushel = 60lbs, Soy = 60lbs, Corn = 56lbs)
// We will assume a standard 60lb unit for general grain comparison, though this varies by crop.
// This is just an estimation metric.
var buPerAcre = lbsPerAcre / 60;
// 5. Calculate Seeds per Square Foot (Metric for drill calibration check)
// 1 Acre = 43,560 square feet
var seedsPerSqFt = seedsPerAcre / 43560;
// 6. Calculate Totals based on Acres input
var totalSeedNeeded = 0;
if (!isNaN(acres)) {
totalSeedNeeded = lbsPerAcre * acres;
}
// 7. Calculate Costs
var costPerAcre = 0;
var totalCost = 0;
if (!isNaN(costPerLb)) {
costPerAcre = lbsPerAcre * costPerLb;
if (!isNaN(acres)) {
totalCost = totalSeedNeeded * costPerLb;
}
}
// Update UI
document.getElementById('resultRateLb').innerHTML = lbsPerAcre.toLocaleString('en-US', {minimumFractionDigits: 1, maximumFractionDigits: 1}) + " lbs/ac";
document.getElementById('resultRateBu').innerHTML = buPerAcre.toLocaleString('en-US', {minimumFractionDigits: 1, maximumFractionDigits: 2}) + " bu/ac (est. @60lb)";
// Format total seed
document.getElementById('resultTotalSeed').innerHTML = totalSeedNeeded.toLocaleString('en-US', {minimumFractionDigits: 0, maximumFractionDigits: 0}) + " lbs";
// Format seeds per sq ft
document.getElementById('resultSeedsSqFt').innerHTML = seedsPerSqFt.toLocaleString('en-US', {minimumFractionDigits: 1, maximumFractionDigits: 1}) + " seeds/ft²";
// Format Costs
document.getElementById('resultCostPerAcre').innerHTML = "$" + costPerAcre.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('resultTotalCost').innerHTML = "$" + totalCost.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
}