This calculator helps you determine the correct amount of herbicide concentrate to mix for your specific application area and target rate. Accurate mixing is crucial for effective weed control and to avoid over-application or under-application, which can be costly and environmentally damaging.
How to Use the Herbicide Rate Calculator
To use this calculator, you'll need a few key pieces of information:
Application Area (Square Feet): This is the total area you intend to spray. If you know your area in acres, you can convert it by multiplying by 43,560 (since 1 acre = 43,560 sq ft).
Herbicide Rate (Ounces per Acre): This is the recommended amount of active ingredient (or formulated product, depending on the label) to apply per acre, as stated on your herbicide product label.
Product Concentration: This describes how much active ingredient is in the herbicide formulation. It's often given in pounds per gallon (lb/gallon) or grams per liter (g/L). Check your product label for this information.
Carrier Volume (Gallons per Acre): This is the amount of water or other carrier you plan to use per acre. This is important for determining the concentration in your spray tank.
Once you enter these values, the calculator will output:
Total Herbicide Needed (Ounces): The total amount of herbicide concentrate required for your entire application area.
Amount to Mix per Gallon (Ounces): The amount of herbicide concentrate to add to each gallon of carrier for your spray tank.
Important Considerations:
Always read and follow the specific instructions and application rates on your herbicide product label. This calculator is a tool to assist with calculations, not a replacement for label instructions.
Ensure your equipment is calibrated correctly to deliver the intended spray volume.
Consider factors like wind, temperature, and target pest/weed stage, which can influence application effectiveness.
function calculateHerbicideRate() {
var areaSqFt = parseFloat(document.getElementById("area").value);
var ratePerAcreOz = parseFloat(document.getElementById("ratePerAcre").value);
var productConcentrationStr = document.getElementById("productConcentration").value.trim();
var carrierVolumeGalPerAcre = parseFloat(document.getElementById("carrierVolume").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(areaSqFt) || isNaN(ratePerAcreOz) || isNaN(carrierVolumeGalPerAcre) || productConcentrationStr === "") {
resultDiv.innerHTML = "Please enter valid numbers for all fields and the product concentration.";
return;
}
// — Process Product Concentration —
var activeIngredientOzPerGallon = 0;
var concentrationParts = productConcentrationStr.toLowerCase().split('/');
if (concentrationParts.length === 2) {
var amount = parseFloat(concentrationParts[0]);
var unit = concentrationParts[1].trim();
if (isNaN(amount)) {
resultDiv.innerHTML = "Invalid product concentration format. Example: '4 lb/gallon' or '480 g/L'.";
return;
}
if (unit === "lb/gallon") {
// Convert lb/gallon to oz/gallon
activeIngredientOzPerGallon = amount * 16; // 1 lb = 16 oz
} else if (unit === "g/l") {
// Convert g/L to oz/gallon
// 1 L = 0.264172 US gallons
// 1 oz = 28.3495 g
activeIngredientOzPerGallon = (amount / 28.3495) * 0.264172; // g/L * (oz/g) * (L/gallon) = oz/gallon
activeIngredientOzPerGallon = amount * 0.264172 / 0.035274; // simpler calculation: g/L * (L/gal) / (g/oz)
} else {
resultDiv.innerHTML = "Unsupported unit for product concentration. Please use 'lb/gallon' or 'g/L'.";
return;
}
} else {
resultDiv.innerHTML = "Invalid product concentration format. Example: '4 lb/gallon' or '480 g/L'.";
return;
}
if (activeIngredientOzPerGallon <= 0) {
resultDiv.innerHTML = "Product concentration must result in a positive amount of active ingredient.";
return;
}
// — Calculations —
var areaAcres = areaSqFt / 43560; // Convert square feet to acres
// Total herbicide needed (ounces)
var totalHerbicideNeededOz = areaAcres * ratePerAcreOz;
// Amount to mix per gallon of carrier
var herbicidePerGallonOz = ratePerAcreOz / carrierVolumeGalPerAcre; // oz of AI per gallon of spray mix
// Amount of product to mix per gallon of carrier
var productPerGallonOz = herbicidePerGallonOz / activeIngredientOzPerGallon; // (oz AI / gal mix) / (oz AI / oz product) = oz product / gal mix
// — Display Results —
resultDiv.innerHTML = `