Calibration means measuring how much liquid your specific sprayer actually delivers over a known area, then comparing that to the label's recommended rate — skipping this step means every application is a guess, regardless of how carefully you mixed the concentrate.
Why Calibration Matters More Than Mixing Accuracy
A perfectly mixed herbicide solution still under- or over-applies if your sprayer's actual output doesn't match what you assume it delivers. Nozzle wear, pressure variation, and walking speed all affect real output in ways a label can't account for on its own.
The Basic Test-Spray Method
- Fill the sprayer with plain water, not herbicide concentrate
- Mark out a measured test area, such as a 10m x 10m section, using string or visible markers
- Spray the test area at your normal walking pace and pressure, exactly as you would during a real application
- Measure how much water was used to cover that area
- Compare the result to the product label's recommended application rate for that area size
Pro tip: Do this test-spray calibration with a completely full tank, not a partially full one. Spray pressure and pattern can shift meaningfully as a tank empties, and calibrating with a partly full tank gives you a rate that won't hold consistent through your entire actual application.
Adjusting If Your Output Doesn't Match
| Result | Adjustment |
|---|---|
| Using less water than the label expects for the area | Walk slower, or increase pressure slightly, to raise output |
| Using more water than the label expects | Walk faster, or check for a worn nozzle delivering too much |
| Output matches closely | Note your walking pace and pressure setting for future consistency |
Recalibrate When Anything Changes
Recalibrate after replacing a nozzle, switching to a different sprayer, or if you notice the spray pattern looking different than usual. Nozzle wear happens gradually and can shift your actual output meaningfully without any obvious visible sign until you test it directly.
Watch out: Don't assume a calibration done once, months or seasons ago, still holds. Nozzles wear over repeated use, and a sprayer that was accurate last season can be meaningfully off by the start of the next one without any obvious external sign.
Frequently Asked Questions
How often should I calibrate my sprayer?
At the start of each season at minimum, and again after replacing a nozzle or noticing any change in spray pattern or pressure.
Should I calibrate with water or actual herbicide?
Always use plain water for calibration testing, since it achieves the same measurement without wasting product or applying herbicide to an area you didn't intend to treat.
Does walking speed really affect application rate?
Yes, significantly — walking faster covers more area with the same amount of liquid, effectively reducing your application rate per square meter, and vice versa.
Browse our full herbicide range, all with clear labeled application rates to calibrate against.