Greenhouse Calibration Worksheet

Learn how to accurately calculate pesticide amounts and calibrate your sprayer for greenhouse and nursery applications using the Greenhouse Calibration Worksheet. This step-by-step video walks you through the process of determining spray volume and chemical needs, helping you ensure proper application rates, reduce waste, and maintain compliance.
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Worksheet at
https://extension.unh.edu/resource/gr...
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Accurate pesticide application—whether outdoors or in a greenhouse—depends on two critical factors: calculating the correct amount of product and properly calibrating the application equipment. Without regular calibration, sprayers may over- or under-apply pesticides, leading to low yields, damaged foliage, soil contamination, and pesticide-resistant pests. It also results in wasted product and increased costs.
Let’s walk through how to calculate pesticide amounts and calibrate your equipment for greenhouse spraying.

Key Terms and Concepts

Chemical: The concentrated pesticide or adjuvant before mixing with water.
Spray: Refers both to the mixture of chemical and water (noun) and the act of applying it (verb).
Clear Water: Water from the supply, used for calibration without chemicals.

Field pesticide labels typically list application rates per acre. In contrast, greenhouse and nursery labels use rates per 100 gallons of spray due to variability in crop type, growth stage, and setup (e.g., hanging plants). Because greenhouse spraying occurs in three dimensions, calibration is necessary to determine how much spray is needed for a specific crop stage, sprayer, and greenhouse.
UNH Cooperative Extension has developed a worksheet to help calculate the total spray volume and chemical required for greenhouse applications. This worksheet also serves as a record for future reference.

Calibration Steps


Record Background Information
Note the crop stage, greenhouse, sprayer, and pressure used. This helps replicate successful applications later.


Select a Test Area
Choose a representative section of the greenhouse. If hangers are present in the spray area, include them in the test area. The area should be large enough to measure water usage accurately—typically around ___ square feet.


Measure the Test Area
Record the length and width, then calculate the area in square feet (length × width).
Example: Length = __ ft, Width = __ ft → Test Area = ___ sq ft


Spray the Test Area with Clear Water
Fill the tank with more water than needed—no chemicals.
Record the initial volume (e.g., 2 gallons).
Spray the test area using normal coverage.
Record the remaining volume (e.g., 0.5 gallons).
Subtract to find the test volume:
Initial Volume – Remaining Volume = Test Volume (e.g., 2 – 0.5 = 1.5 gallons)


Measure the Full Spray Area
Measure the entire area to be sprayed (length × width), subtracting any unsprayed sections like walkways.
Example: Length = __ ft, Width = __ ft, Walkway = __ ft → Spray Area = __ sq ft


Calculate Total Spray Volume
Use the formula:
(Test Volume × Spray Area) ÷ Test Area = Spray Volume
Example: (1.5 gal × 5,000 sq ft) ÷ 500 sq ft = 15 gallons


Determine Chemical Amount
Refer to the pesticide label for the application rate.

If the rate is per gallon:
Multiply rate × Spray Volume
If the rate is per 100 gallons:
Multiply rate × Spray Volume ÷ 100
Example: Label rate = 2 lbs/100 gal, Spray Volume = 15 gal
(2 × 15) ÷ 100 = 0.3 lbs of chemical



Repeat this step for each chemical being added.

Mixing Instructions
Fill the tank halfway with clear water. Add the total calculated chemical amount. Then, continue filling with water to reach the full spray volume. Always follow the mixing instructions on the product label.

Final Notes
Spending a few minutes on calibration ensures pesticides are applied at the correct rate, improving crop production and saving money. For more guidance, check out the additional programs in this series on mixing, applying, and cleaning greenhouse sprayers.

Presented by:
Jonathan Ebba
University of New Hampshire Extension
In partnership with:

NH Department of Agriculture, Markets & Food
NH Fruit Growers Association
Hillside Meadows Ag Consulting
George Hamilton, Project Coordinator

UNH Cooperative Extension is an equal opportunity educator and employer. This content is funded in part by an Integrated Pest Management grant from the NH Department of Agriculture. Mention of trade names or products does not imply endorsement.