Herbicide / Pesticide Tank Mix Calculator

Filling a sprayer correctly means matching the chemical in the tank to the acres that tank will actually cover, not to the whole field. This calculator works out how many acres each tankful treats and how much product to pour in, including the awkward partial last tank, so every acre gets the labeled rate.

How it works

The math hinges on how many acres one tank of carrier covers:

acres per tank = tank size (gal) / spray volume (GPA)
product per tank = acres per tank × label rate per acre
total tanks = field acres / acres per tank
total product = field acres × label rate per acre

The number of tanks is split into whole full tanks plus a final partial tank sized to the leftover acres, so you mix only what you need and avoid disposing of leftover spray solution.

Example

For example, a 24 oz/acre herbicide applied at 15 GPA from a 300-gallon tank: each tank covers 300 / 15 = 20 acres and takes 20 × 24 = 480 oz of product. Treating 70 acres needs 3 full tanks (60 acres) plus a partial tank for the final 10 acres holding 150 gallons of water and 240 oz of product, and 1,680 oz of product total.

Choosing the right spray volume (GPA)

Gallons per acre is not a fixed number — it is set by your nozzle selection, boom pressure, and travel speed. Getting it right before mixing is essential:

• Too low a GPA can give poor coverage, especially on broadleaf weeds with waxy or hairy leaves that repel small droplets.
• Too high a GPA wastes carrier, slows application, and can increase off-target drift from larger droplets at higher pressures.
• Product labels often specify a minimum GPA for effective performance. Always use at least the label minimum.

To verify your actual GPA before mixing: run the sprayer on water over a measured distance, collect output from one or more nozzles for a timed interval, and calculate. Calibrating the sprayer before the season starts prevents applying too much or too little product across the entire job.

The partial tank problem

The most common sprayer error is overmixing for a partial last run. If you mix a full tank when only a fraction of it is needed to finish the field, you end up with leftover spray mix that must be re-applied (at the risk of over-treating already-sprayed areas) or disposed of as regulated waste.

This calculator prevents that by computing the partial tank’s water and product quantities exactly. Mix only what the partial tank calculation specifies, fill the tank to that water volume first, add the exact product amount, and run it out on the remaining acres.

Tank mixing order matters

The product quantities here tell you how much to add, not in what order to add them. A safe general sequence for mixing multiple products:

1. Fill tank to half capacity with clean water, agitating throughout.
2. Add soluble packets or water-dispersible granules (WDGs) first and agitate until dissolved.
3. Add wettable powders (WPs) next.
4. Add soluble liquids and emulsifiable concentrates (ECs).
5. Add adjuvants, surfactants, and oils last.
6. Top off with remaining water.

Always check the label for product-specific mixing order instructions, since some combinations require a different sequence to prevent incompatibility.

Legal compliance note

Using a herbicide at a rate above the label maximum is illegal under FIFRA in the United States and equivalent regulations in other countries. This calculator outputs the rate you entered — it does not validate whether that rate is within label limits. Always read and follow the current product label, which is the legal document governing use, before mixing.