Yield estimates are only as accurate as the field area they represent. Repeat counts at multiple locations to increase your accuracy. Factors such as water availability, insects, diseases and weeds can also affect seed fill and final yields. As the corn plants mature and get closer to black layer, these stressors have less of an effect on yield. The method below describes one way to estimate corn yields.

  1. Determine the number of harvestable ears in 1/1000 of an acre.
    In 30 inch rows, 1/1000 of an acre represents 17’5”. Count the number of harvestable ears in this section. Record the number of harvestable ears.
  2. Examine at least 3 ears in this section and count the number of rows (this will always be an even number) as well as the number of kernels in each row. To avoid hand picking the best ear, look at every 5th ear.
    Do not count the butt or tip kernels. Record the average number of rows and kernels per row.
  3. Estimate yield by multiplying the number of ears in 1/1000 of an acre (1) by the average row number by the average kernels per row (2). Divide this number by 90 (kernel number (thousands) per bushel). You can play with the kernel number/bushel depending on growing conditions or kernel size.

Excellent growing conditions/Large kernel size – 75-80 (thousand) kernels per bushel
Average growing conditions/Average kernel size – 85-90 (thousand) kernels per bushel
Poor growing conditions/Small kernel size – 95-100 (thousand) kernels per bushel


[18 kernel rows x 26 kernels per row x 31 ears in 1/1000 of an acre]/90 = 161 bu/acre

Laura Johnston, CCA-ON, Maizex Seeds Yield Specialist, West Elgin County
Twitter: @lmjohnston8