Sprayer Calibration & Spray Mix Calculator

Sprayer calibration calculator and spray mix per tank

Spraying the right dose means knowing two things: how many litres of spray your sprayer puts on a hectare or an acre, and how much product goes into each tank. This sprayer calibration calculator works out the first from a simple bucket-and-stopwatch test — nozzle output, walking or tractor speed and spray width — or from the water used on a measured test strip. It then turns the rate printed on the product label into millilitres or grams per 15 or 16 litre knapsack tank, or per 200–2,000 litre tractor tank.

It works in metric (L/ha and L/acre) and US units (gallons per acre), handles label rates given per hectare, per acre, per litre of water or as a percentage, and counts the tank loads and total product for your field in acres, hectares or bigha. It never recommends a product or dose: it only does the arithmetic on the label rate you type.

How to calibrate a sprayer and work out the mix

1. Fill the sprayer with clean water. Spray from one nozzle into a measuring jug for 30 seconds and type the millilitres collected and the seconds.
2. Mark 50 or 100 m in the field, walk or drive it at spraying pace with the pump working, and type the distance and seconds. Enter the number of nozzles and the spray width or nozzle spacing.
3. Or choose Spray a test area: spray a measured strip and type the litres needed to refill the tank to the mark.
4. Under Spray mix, enter the tank size and the label rate with its unit. Keep Use my calibration above ticked, or type the spray volume yourself.
5. Enter the area to spray and read the product per tank, the number of tanks, total product and water, then copy the mix.

Sprayer Calibration Calculator features

Sprayer calibration formulas

The 600 converts minutes to hours and m² to hectares; 5,940 does the same for gallons, miles and inches.

• Metric: L/ha = nozzle output (L/min) × 600 ÷ (speed in km/h × nozzle spacing in m). Example: 0.8 L/min × 600 ÷ (3 km/h × 0.5 m) = 320 L/ha.
• US: GPA = 5,940 × GPM per nozzle ÷ (MPH × nozzle spacing in inches). Example: 0.25 GPM at 6 mph and 20 in: 5,940 × 0.25 ÷ 120 = 12.4 gallons per acre.
• Speed: km/h = metres ÷ seconds × 3.6; 100 m in 120 s is 3 km/h, a typical walking pace with a knapsack.
• Test area: L/ha = litres used × 10,000 ÷ m² sprayed; 3.2 L on 100 m² is 320 L/ha, or about 129.5 L per acre.

Working out product per tank

If the label gives a rate per hectare or per acre: product per tank = label rate × tank size ÷ spray volume. At 500 ml per hectare with a 320 L/ha spray volume, each litre of spray needs 500 ÷ 320 = 1.56 ml, so a 16 L tank gets 25 ml and covers 500 m². One acre needs 129.5 L of spray: 8 full tanks and a last tank of 1.5 L, using 202 ml of product in all.

If the label gives a rate per litre of water, multiply by the tank size: 2 ml per litre is 32 ml in a 16 L tank. A 1% spray is 10 ml per litre. When the label gives both a per-area dose and a spray volume, follow both — your calibration tells you whether your sprayer delivers that volume. For liquid-strength problems, the dilution calculator handles C₁V₁ = C₂V₂, and fertilizer doses are in the fertilizer calculator.

Common calibration mistakes

• Timing the walk on a road instead of in the crop — speed in the field is slower, so the real volume is higher.
• Ignoring worn nozzles: a nozzle putting out 10% more than a new one should be replaced.
• Changing pressure or pumping rhythm after calibrating; a knapsack must be pumped steadily.
• Mixing per-acre and per-hectare figures: one hectare is 2.471 acres.