The application rate equals the amount of pesticide dispersed divided by the distance covered. Sometimes the label will give specific amounts for application procedure and no calculations will be needed. For large areas you may want to test on smaller sites and then calculate the appropriate application rate for the area you will cover.
When you know that you will be treating a small area or will be using equipment that only carries a small amount of pesticide, your test site can be small. For example, choose an amount that would be one-quarter of what you would use on the site.
The same goes for larger treatment areas or for equipment that carries a large amount of pesticide—test on a larger site. In this situation, you will want to use the actual recommended amount. To find a rate per acre, multiply your test output by 43.56. This is the number of square feet in one acre (43,560) divided by 1,000.
Do not neglect checking calibration. Just because you have it adjusted correctly does not mean it will maintain its effectiveness. Wear and tear, corrosion, and clogging can change the rate of application. Keep this in mind and you will save yourself problems later. Pay attention to be sure that you are treating the same amount of area as you had figured. If you are coming out above or below that amount, recalculate and check your calibration.