What is the 5,940 in the sprayer calibration formula?

It is a unit constant, not a fudge factor. Gallons per acre equals 5,940 × nozzle output in gal/min ÷ (speed in mph × nozzle spacing in inches); the 5,940 carries the conversion from minutes, miles and inches into acres. This page does the same arithmetic in SI internally and converts once, so it gives the same answer in litres per hectare without a second constant.

Do I use catch-can output or the chart on the nozzle box?

Catch the nozzles. A chart tells you what a new nozzle does at a stated pressure; a worn set sprays more, a partly blocked one less, and the difference between them is exactly what calibration exists to find. Measure several nozzles across the boom and use the average.

How do I check my forward speed?

Time the sprayer over a measured distance in the field, loaded, in the gear and at the engine speed you will actually spray at — not on the road. Speed enters the rate directly, so a tractor going 10 % faster than the display claims applies 10 % less mix per acre.

Why does the product rate need to say "per acre" or "per hectare"?

Because a label written in one and a sprayer set in the other is one of the commonest ways a field gets a wrong dose. The page asks which basis the label uses and converts it to the tank, rather than assuming.

Sprayer calibration calculator

Nozzles delivering 0.35 gal/min at 4.5 mph on 20-inch spacing put out 23.1 gal/ac, which is 216.1 l/ha. Twenty-four of those nozzles make a boom 12.19 m wide, a 400-gallon tank covers 17.32 acres at that volume, and a label rate of 1.5 units of product per acre means 25.97 units go into every full tank. The line no competitor prints is the last one: save a field and the sheet says how many full fills the job takes and how much mix is left in the final tank.

Your answer

Spray volume23.76 gal/ac

The same rate the other way: 222.3 l/ha

Field job sheet

Type the field area above (or pick a saved field) to get the whole-field total, the last bag and a sheet to print or send.

How the answer is worked out

Calibration answers one question — how much liquid lands on an acre — and then three that follow from it.

Spray volume. Each nozzle covers a strip as wide as the nozzle spacing. In one minute the sprayer travels speed × 88 feet per mph, so the area one nozzle treats per minute is known, and the nozzle’s own output divided by that area is the rate. Everything else on the page is derived from it.
Boom width = nozzle spacing × number of nozzles. It is what the field is actually covered in, and what the pump has to feed.
Pump demand = output per nozzle × number of nozzles, printed in l/min because that is how pumps are rated.
Acres per tank = tank size ÷ spray volume per acre.

The last tank is the number that is missing everywhere else

A rate per acre is the beginning of the job, not the end of it. What the operator needs at the yard is how many full tanks to mix, how much product goes in each, and what to put in the final part-tank so that the field finishes empty and nothing is left to dispose of. That is what the job sheet prints, and it is why the field is worth saving on this site: enter it once on the acreage page and every tool, this one included, works on the same area.

Product per tank is not the same as product per acre

Mixing “the label rate” into a tank is how a field gets over- or under-dosed. The product that belongs in one full tank is the label rate per acre multiplied by the acres that tank covers — 1.5 per acre over 17.32 acres is 25.97, not 1.5. The page prints that figure in whatever unit the label is written in, because litres, quarts, pounds and grams all appear on labels and none of them changes the arithmetic.

Read the label for the rest: water volume limits, buffer zones, tank-mix partners and re-entry intervals are legal conditions of use, and a calculator does not replace any of them.

A worked example

Every figure below is computed by the calculator above from this case — nothing here is typed in by hand:

Output of one nozzle: 0.35
Flow unit: gal/min
Forward speed: 4.5
Speed unit: mph
Spacing measured in: in
Nozzle spacing on the boom: 20
Number of nozzles: 24
Tank size: 400
Tank unit: gal
Product rate: 1.5
Product rate is per: acre

Spray volume:23.1 gal/ac

The same rate the other way: 216.1 l/ha
Boom width: 12.19 m
What the pump must deliver: 31.8 l/min
One tank covers: 17.32 ac
Product in one full tank: 25.97

Worked by Agrimetra with the same engine the calculator above runs.

What this means in the United States

The extension formula behind sprayer calibration is gallons per acre = 5,940 × nozzle output in gal/min ÷ (speed in mph × nozzle spacing in inches), and the 5,940 is a unit constant, not a fudge factor. Calibration against the actual output of the nozzles on the boom is what makes a label rate mean anything.

Questions growers actually ask

What is the 5,940 in the sprayer calibration formula?: It is a unit constant, not a fudge factor. Gallons per acre equals 5,940 × nozzle output in gal/min ÷ (speed in mph × nozzle spacing in inches); the 5,940 carries the conversion from minutes, miles and inches into acres. This page does the same arithmetic in SI internally and converts once, so it gives the same answer in litres per hectare without a second constant.
Do I use catch-can output or the chart on the nozzle box?: Catch the nozzles. A chart tells you what a new nozzle does at a stated pressure; a worn set sprays more, a partly blocked one less, and the difference between them is exactly what calibration exists to find. Measure several nozzles across the boom and use the average.
How do I check my forward speed?: Time the sprayer over a measured distance in the field, loaded, in the gear and at the engine speed you will actually spray at — not on the road. Speed enters the rate directly, so a tractor going 10 % faster than the display claims applies 10 % less mix per acre.
Why does the product rate need to say "per acre" or "per hectare"?: Because a label written in one and a sprayer set in the other is one of the commonest ways a field gets a wrong dose. The page asks which basis the label uses and converts it to the tank, rather than assuming.

Last updated: September 22, 2026

Sources

Michigan State University Extension — sprayer calibration (checked September 22, 2026)
US EPA — pesticide labels and how to read them (checked September 22, 2026)