Work out knapsack sprayer dose instantly with clear inputs, formula shown and shareable results.
A knapsack operator works tank by tank, so the label's per-acre rate must be converted to a per-tank dose: product per tank = rate per acre x tank capacity / spray volume per acre. Getting this wrong is the most common cause of crop damage and residue failures in smallholder spraying.
Dose per tank
Product per tank = rate per acre x tank volume / spray volume per acre
Tank loads
Tanks = spray volume per acre x area / tank capacity
Pesticide overdose harms crops, applicators and consumers and breaches label law. Wear the personal protective equipment stated on the label and observe the pre-harvest interval.
Fill the tank with plain water, spray a marked 100 m2 strip at your normal walking pace and pressure, measure the water used, then multiply by 40.47 to get litres per acre.
Use a graduated measuring cylinder or syringe, never a bottle cap. For very low doses, make a stock solution of known strength and measure a larger volume of that instead.