Yield Monitor Calibration Calculator

Yield per acre is the corrected load weight divided by Harvested Area, and Harvested Area is Header Width multiplied by Pass Distance -- so for the same Load Weight, covering more ground on the calibration pass spreads that same weight over more acres, which lowers the calculated yield per acre. This is why an accurate, consistently measured Pass Distance (a half-mile, or 2,640 feet, is a common calibration-pass length) matters as much as an accurate scale weight.

The correction formula scales the load weight down by the ratio of dry matter remaining at actual moisture versus dry matter at standard moisture -- so a wetter load has more of its total weight made up of water that doesn't count as harvested dry grain, and the correction removes that extra water weight. This is the same formula grain elevators use to dock or credit deliveries for moisture, which is why it's the standard way to make yield comparisons fair across loads harvested at different moisture levels.

Those are the USDA standard bushel weight and standard moisture for corn, the most commonly calibrated row crop for combine yield monitors, as documented in Ohio State University Extension's published grain-standards reference (AGF-503, "Bushels, Test Weights, and Calculations"). If you're calibrating for a different grain, replace both defaults with that crop's own standard figures -- soybeans use 60 lbs/bushel at 13% standard moisture, and wheat uses 60 lbs/bushel at 13.5% -- since using corn's standard weight for a different crop would produce a yield figure with the wrong units.

The Calibration Factor is the ratio between your true, scale-verified Load Weight and the yield monitor's own raw Monitor Recorded Weight for that same calibration pass. Most combine yield monitors have a built-in calibration routine that asks for exactly this kind of weigh-wagon-vs-monitor comparison -- enter the true weight there (or apply this factor manually to the monitor's readings) so the rest of the field's yield map reflects ground truth rather than an uncorrected sensor estimate.

Most combine yield monitor displays show a running or per-load mass total from the mass-flow sensor before any calibration factor has been applied -- note that raw, uncalibrated figure for the same calibration pass you're weighing on a scale. Reading the monitor's already-calibrated total instead would compare the scale weight against a number the monitor already adjusted, which defeats the point of calibrating it.