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Herbicide Mix Per Acre Calculator

Mix a sprayer correctly: total product and water for your acres, plus how much product goes in each tank at your spray volume.

Product rate per acre

Acres to spray

Spray volume

Tank capacity

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How it works

Acres/tank = tank ÷ GPA · Product/tank = rate × acres/tank · Total product = rate × acres · Total water = acres × GPA

The label sets the product rate per acre; your sprayer’s spray volume (gallons per acre, GPA) sets how many acres one tank covers. Multiplying the acres a tank sprays by the per-acre rate gives the product to pour into that tank, so the mix comes out at the labeled rate regardless of tank size. Getting this right prevents both under-dosing, which lets weeds escape, and over-dosing, which wastes chemical, risks crop injury and can violate the label.

Worked example

A 300-gallon tank at 15 GPA covers 300 ÷ 15 = 20 acres. At 32 oz/acre, that tank needs 32 × 20 = 640 oz (5 gallons) of product. Spraying 40 acres total takes 1,280 oz (10 gallons) of product and 600 gallons of water across 2 tank loads.

Frequently asked questions

What is GPA and why does it matter?

GPA is gallons of spray solution applied per acre — the carrier volume, not the product rate. It is set by nozzle size, pressure and speed. GPA decides how many acres a tank covers and affects coverage, but the product rate per acre is what must match the label.

How do I convert ounces to gallons?

There are 128 fluid ounces in a US gallon, so divide ounces by 128. The calculator shows both so you can measure product in whatever unit your jug uses. Always follow the label’s own units — some rates are in pints, quarts or pounds of dry product.

Does the order I add things to the tank matter?

Yes. Follow the label’s mixing order — typically fill part-way with water, add products in the WALES/dry-then-liquid sequence with agitation running, then top off. Wrong order can cause products to clump, gel or fall out of suspension. This tool covers quantities, not the mixing sequence.

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This calculator is for educational purposes. Double-check important results before acting on them.