1 · Gallons-per-acre (GPA) calculator
GPA is the master number. It comes from three things: how fast liquid leaves the nozzles (flow), how fast you fly (speed), and how wide each pass covers (swath).
GPA = (flow × 495) ÷ (speed × swath). Acres/hr = (speed × swath × 5280) ÷ 43,560. "Theoretical" ignores turns, refills, and battery swaps — real output is typically 60–75% of this.
2 · Swath overlap — the picture
Fly passes too far apart and you get skips (streaky control). Too close and you double-apply (wasteful, illegal overlap). Most ag drones plan for a modest overlap. Move the slider and watch coverage change.
Effective swath shrinks as overlap rises: at 10% overlap a 20 ft boom effectively covers ~18 ft, so you fly more passes to cover the same field.
3 · Tank loads for a field
Knowing GPA and tank size tells you how many loads (and battery/water stops) a field will take.
How to actually calibrate (field method)
- Read the label for the target GPA and any droplet-size requirement.
- Fill with clean water and fly a measured test area at your planned speed and height.
- Measure what came out — refill and record the volume used over the known area.
- Compare to target. Adjust flow (nozzles/pump), speed, or swath until measured GPA matches the label.
- Re-check after any change to nozzles, height, or payload — and log it.
Droplet size, in one breath
Finer droplets = better coverage but more drift risk; coarser droplets = less drift but you need enough of them to cover the target. Nozzle/atomizer choice and pressure set droplet size. The label often specifies a minimum droplet category — respect it. Learn the full picture in the drift management guide.
Method and formulas follow standard extension calibration guidance (e.g., land-grant university pesticide applicator manuals). Always calibrate to the specific label and your equipment; figures here are planning aids, not label rates.
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