Calculating Corn Harvest Loss: How to Count Kernels and Ears Dropped

Once harvest starts, it’s a mad dash to the finish line. Time is money, and stopping or delaying your harvest is the furthest thing from your mind.

But corn kernel and ear drop can take unwelcome bites from your bottom line. For example, two dropped kernels of corn per square foot equals harvest losses totaling one bushel per acre.¹ Taking the time to measure and minimize losses is time well spent to ensure the maximum bushels make it from the field to the bin.

Types of corn harvest loss

To minimize harvest loss, identify when and how the loss occurred to make appropriate adjustments.

Pre-harvest losses: Caused by disease and insect pressure and inclement weather, pre-harvest losses include ear drop or stalk lodging, where the corn never makes it into the header.

Header losses: Header or gathering losses occur during the harvesting process when ears or kernels are dropped or left behind as a result of improper combine settings and less than ideal plant condition.

Threshing and separating losses: These occur when ears come in contact with combine components such as gathering snouts, snapping bars, snapping rolls and the cross auger, causing some kernels to be shelled out and lost or remain attached to the cob.²

How to measure corn harvest losses from the combine

You can measure both kernel and ear loss using the following methods.

Measuring kernel loss

1. Stop the combine, without clearing it, at least 100' from row ends.
2. Build a 1' by 1' measuring frame (PVC pipe with 90-degree elbows works well) and drop the frame onto the ground in a spot just harvested, counting the loose kernels within the frame. Count kernels in the frame at several locations in the field around the combine and average the results. This will give you the most accurate harvest loss assessment.
3. To calculate the loss in bushels per acre, divide your average per-square kernel count by 2.
4. Divide the figure from Step 3 by your measured yield per acre, then multiply by 100 to find the percent loss per acre.
   

For example, let’s say your average yield per acre is 186.5 (the national average in 2025)³

If you count an average of 10 kernels within the measuring frame, you would calculate the percent lost per acre as follows:

10 ÷ 2 = 5 (bu per acre)

5 ÷ 186.5 = 0.0268

0.0268 ✕ 100 = 2.68% loss per acre

Measuring ear loss

To put it simply, each ear per 100 plants equals roughly 1% loss. Here’s the breakdown:

1. Pick a row behind your combine and count any ears on the ground within 87 feet (30 paces or so) of the back of the combine. Every ear you find within this length between 30"-wide rows equates to about one bushel per acre of harvest loss from ears.
2. Divide the figure from Step 1 by your measured yield per acre, then multiply by 100 to arrive at your percent loss per acre.
   

For example, let’s say you count 12 ears on the ground. Here’s how you would calculate the ear loss: 12 ÷ 186.5 = 0.064

0.064 ✕ 100 = 6.4% loss per acre

How to minimize corn harvest loss

Frequently measuring corn harvest losses, even up to multiple times per day, is recommended to accurately monitor combine performance and make necessary equipment adjustments to minimize harvest loss in your field.

Measure corn harvest losses early to mitigate yield reductions

Harvest losses are an unfortunate but inevitable reality in crop production. While we wish there were a magic bullet to avoid losses, some loss is always expected. Under proper management, acceptable corn harvest loss should remain around 1 to 2%.

Measuring losses early into harvesting can easily help you make harvest adjustments needed to protect your yield. If you have questions about estimating yield and harvest losses, reach out to a nearby extension office agent or your regional BASF representative.

________________________________________________

Endnotes

1. “Measuring Field Losses From Grain Combines.” University of Georgia, 29 July 2026, site.extension.uga.edu/colquittag/2026/07/measuring-field-losses-from-grain-combines/. Accessed 15 Oct. 2026.
2. Isaacson, Ashley, et al. “Combine Adjustments to Minimize Corn Harvest Losses.” Penn State Extension, 16 Sept. 2025, extension.psu.edu/combine-adjustments-to-minimize-corn-harvest-losses. Accessed 15 Oct. 2026.
3. “Crop Production - 2025 Summary.” USDA, Jan. 2026, esmis.nal.usda.gov/sites/default/release-files/795725/cropan26.pdf. Accessed 15 Oct. 2026.