Spray Mix Calculator
Mix the right amount of chemical and water for a paddock spray job. Enter the product's label application rate, the area to cover, your water rate and tank size, and it returns the total product and water needed, how many full tank-loads that is, and — most useful in the field — how much product to add to each full tank.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the product application rate in millilitres per hectare (mL/ha) from the chemical label.
- Enter the area to spray in hectares, then your water application rate (L/ha, default 100) and spray tank capacity (L, default 1000).
- Read off the total product and water, the number of full tank-loads, and the product to add per full tank.
How it works
Total product = application rate × area (mL, also shown in litres). Total spray volume = water application rate × area (L). Full tank-loads = total spray volume ÷ tank capacity, rounded up to the next whole tank. Each full tank covers a fixed area equal to tank capacity ÷ water rate (hectares per tank), so the product to add to each full tank = application rate × hectares per tank. Measuring product per tankful this way keeps the mix at the correct concentration on every load.
Worked example
Worked example. Rate 200 mL/ha over 50 ha at 100 L/ha of water with a 1000 L tank: total product = 200 × 50 = 10,000 mL = 10 L; total spray volume = 100 × 50 = 5,000 L; full tank-loads = ceil(5,000 ÷ 1,000) = 5. Each full tank sprays 1,000 ÷ 100 = 10 ha, so add 200 × 10 = 2,000 mL of product per full tank.
Common mistakes
- Ignoring the label — the registered label rate, water volume and directions always override any calculator figure.
- Adding the whole product amount to the first tank instead of the per-tank dose, which over-concentrates early loads and leaves later ones under-dosed.
- Mixing water rate (L/ha) and application rate (mL/ha) up, or entering product in litres when the field expects millilitres.
Frequently asked questions
Does the last (partial) tank use less product?
Yes. The per-full-tank figure is for a completely filled tank. On the final part-filled tank, dose it for the area it will actually cover: remaining hectares × application rate. The calculator rounds tank-loads up because the last tank is usually only partly full.
Should I follow this calculator or the chemical label?
Always the label. This tool is a mixing aid only — the product label sets the legal rate, water volume, protective equipment, mixing order and withholding periods, and it overrides any number here.
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Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.