Combine Calibration for Accurate Yield Data

• Calibrating your combine and yield monitor prior to harvest is critical for obtaining accurate yield data.
• Recalibration is necessary when switching to a different grain type or if substantial moisture content changes occur throughout the season.
• Always refer to the manufacturer’s manual for specific combine and yield monitor calibration procedures.

Calibration Tips

Yield monitors do not directly measure grain yield and instead use data from sensors mounted in a combine to estimate yield. These sensors measure grain moisture, temperature, and flow over a known distance. Monitors collect this information every second or two and store it on a memory device, and the software uses an equation to estimate dry grain yield per acre for that area.

Calibrate yield monitors prior to harvest or when switching crops. Calibration procedures can be found in the operation manual as each monitor may be different. Harvest records can be used to create yield maps for post-harvest analysis to inform future crop management decisions.

It is important to make sure the support equipment used for calibration are accurate. Grain carts should be checked with a certified scale weight, and hand-held moisture testers should be calibrated with the same grain type to be harvested. If these tools do not provide accurate readings, it will only increase the inaccuracies in the yield data collected.

Prior to calibration, back up data from the previous season, if not already completed and ensure there is enough memory available to record the next season’s data. Inspect all sensors, wires, cables, and connections to make sure that they are clean and working properly and download any available software updates.¹

Yield Monitor Accuracy

Yield monitors use multiple sensors to accurately estimate yield. If any of these sensors are not functioning properly or are not accurately calibrated, then the accuracy of the yield monitor will be reduced.²

Mass Flow Sensor Calibration

The mass flow sensor or impact sensor is the most important part of the combine to calibrate for accurate yield data.³ Most yield monitors operate by measuring the force that moving grain imparts on an impact sensor as the grain moves through the combine and into the holding bin.⁴ Proper calibration requires harvesting three to five separate loads of grain at different flow rates. Calibration loads should be between 3,000 to 6,000 pounds, or 50 to 100 bushels, and each load weighed with a weigh wagon or other accurate scale.^2,5 Different flow rates can be achieved using one of the following two methods when harvesting calibration loads:

1. Harvest at the same speed with different amounts of the header engaged in the crop.
   Example: If you have a 12-row corn head, run four calibration loads by harvesting 2, 4, 8, and 12 rows all at the same harvest speed.
2. Harvest at different speeds using the full header width.
   Example: If you generally harvest at 3.5 MPH, run four calibration loads by harvesting at 1, 2, 3, and 4 MPH with the full header width engaged in the crop.

Running multiple calibration loads generally provides greater accuracy when calibrating yield monitors. Some manufacturers may only suggest that one grain load is necessary for calibration. If a yield monitor only accepts a single calibration point, then the only option is to calibrate using the full header width at harvest speed.⁴ Multi-load calibration procedures take more time but provide greater accuracy by capturing more of the full range of grain flow rates encountered during harvest.

Moisture Sensor Calibration

While harvesting calibration loads, collect a grain sample and determine the grain moisture content of each sample using a high-quality meter that has been recently calibrated. Check the moisture sensor accuracy by using this data when entering the calibration data for the mass flow sensor. Refer to the manufacturer’s manual for details on how to set the offset or calibrate the machine’s moisture sensor.

Distance Traveled and Ground Speed

Accurate ground speed and distance traveled are necessary to accurately record yield per acre. Most yield monitors accurately determine these measurements using GPS signals. However, older systems may rely on measurements of wheel revolutions and calculated distance and speed based on wheel size. Always refer to the operator’s manual for calibration procedures.

Header Height Setting

The header height settings determine the beginning and ending of data logging. Raise and lower the header to make sure the stop height switch operates correctly. Failure to disengage the header height switch at the ends of rows can result in inaccurate acreage estimates and yield data.

Check for Calibration Accuracy Throughout the Season

Calibration accuracy of yield monitors can be influenced by the following:⁵

• Yield levels outside of the range of grain flow rates used for calibration,
• Seasonal changes in temperature and grain moisture content, and
• Differences in grain test weight, grain shape, and field topography.

Spot-check your yield monitor multiple times during the harvest season to ensure accuracy. Recalibrate as you move from one crop to another or when you encounter significant changes in grain moisture content or test weight. Always refer to the machine’s operating manual for specific details on completing the calibration process.

Sources

¹Hawkins, E., and Fulton, J. 2024. Tips for calibrating grain yield monitors—Maximizing value of your yield data. Ohio State University Extension. ANR-8. https://ohioline.osu.edu/factsheet/anr-8.

²Jodlowski, C. 2023. Calibration is key to harvest data utilization. Illinois Soybean Association. ILSOY Advisor. https://www.ilsoyadvisor.com/calibration-is-key-to-harvest-data-utilization/

³Pennington, D. 2016. Yield monitor calibration procedure. Michigan State University Extension. https://www.canr.msu.edu/news/yield_monitor_calibration_procedure.

⁴Luck, B. 2017. Calibrate your yield monitor for greater accuracy during harvest. University of Wisconsin extension bulletin A4146. https://learningstore.extension.wisc.edu/products/calibrate-your-yield-monitor-for-greater-accuracy-during-harvest-p1868.

⁵Nielsen, R. 2018. Yield monitor calibration: garbage in, garbage out. Purdue University Extension Corny News Network. https://extension.entm.purdue.edu/newsletters/pestandcrop/article/yield-monitor-calibration-garbage-in-garbage-out/.

Web sites verified 07/28/2025.
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