Skip to content
ENExplore Calculators

Knapsack Sprayer Dose Calculator

Work out knapsack sprayer dose instantly with clear inputs, formula shown and shareable results.

About Knapsack Sprayer Dose Calculator

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.

Formulas

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

Worked example

With the default values below, Knapsack Sprayer Dose Calculator returns Product Per Tank Load of 40.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Product Rateminimum 0.1 mL or g per acre
500 mL or g per acre
Spray Volumeminimum 1 L per acre
200 L per acre
Knapsack Tank Capacityminimum 1 L
16 L
Area To Sprayminimum 0.01 acre
2 acre

Results

Product Per Tank Load
40.00
Tank Loads Needed
25.00
Total Product Required
1,000.00
Total Water Required
400.0

Step by step

  1. 1Values used
  2. 2Dose per tank
  3. 3Tank loads
  4. 4Product Per Tank Load= 40.00
  5. 5Tank Loads Needed= 25.00
  6. 6Total Product Required= 1,000.00
  7. 7Total Water Required= 400.0

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • 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.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

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.

Frequently Asked Questions

How do I find my actual spray volume per acre?

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.

What if the dose per tank is a tiny volume?

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.

Related Calculators

Knapsack Sprayer Dose Calculator | Calcrivo