I posted this below but thought it deserved its own thread:I get a bit scared when I see some of the posts on how to calibrate, mix or use agrichemicals. Ive been in this business for nearly 30 years and I have used the following hundreds of times. It works for any sprayer. Just remember to keep the pressure pumped up and dont go from max to none.


Easy Backpack Sprayer Calibration


Step 1: Mark off a area 18.5 feet by 18.5 feet
Step 2: Spray the area uniformly with water noting the number of seconds required
Time Required_____________seconds
Step 3: Spray into a bucket for the same number of seconds.
Step 4: Measure the number of ounces collected in bucket
Volume sprayed____________ounces
Step 5: The volume sprayed equals gallons per acre
Gallons per acre___________gallons

Adding the correct amount of herbicide to the tank

Step 6: Record Gallons/acre from Step 5 _____GPA
Step 7: Determine Volume of Spray tank
Tank Volume_____________gallons
Step 8: From Product Label, determine rate per acre of concentrate. Rate/acre__________pints/ounces
Step 9: Calculate the amount of concentrate to add to one backpack or sprayer fill:
A: Gallons in sprayer____2____
B: Sprayer Rate per acre of water___20____
C: Divide A by B….2/20=1/10 acre
D: From Label Rate in Step 8, multiply rate per acre by C. Example 1 pt/acreX1/10= 1/10 pt per sprayer fill.

Liquid Conversions
1 Cup = 8 ounces 1 Quart = 4 cups
1 Cup = 16 Tablespoons 1pint =2 cups
16 Tablespoons = 48 teaspoons 1 pint = 16 ounces
1 Tablespoon =3 teaspoons 1 ounce = 2 Tablespoons
1 pint = 96 teaspoons 1 pint = 32 Tablespoons
1 teaspoon = approx. 7cc 1 Tablespoon =20 ml=20cc
1 Quart = 64 Tablespoons


 In the example above, you would add 1/10 of a pint per tank full to achieve 1 pint per acre. 1/10 of a pint is 3.2 Tablespoons or 64 ml or 64 cc’s.
 For powders, you must compute the weight in ounces per teaspoon or tablespoon to figure the rate per acre. A good low cost tool for that is a postal scale. Many labels have conversions to rate per 1000 ft/square in teaspoons or tablespoons.
 To calculate rate your sprayer puts out per 1000 ft square, divide the gallons per acre in step 5 by 43. If rate per acre is 30 gallons, the rate per 1000 ft square is .70 gallons per 1000 ft square. If a product rate is 2 tablespoons per 100oft square, then in a 3 gallon sprayer you would divide 2 Tablespoons by .70= 2.85 Tablespoons per gallon. 2.85 Tablespoons per gallon times 3gallons in sprayer= 8.5 Tablespoons per tank fill.


Rate per Acre Rate per 1000 ft square
1 Quart 1.5 Tablespoons
1 Pint 2.25 Teaspoons
8 ounces 1.1 teaspoons

Thanks a lot. I' ve printed it out and will use it when I get my new sprayer. You have probably helped more people than me. [&:]terry