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How to Calculate Corn Yield
The classic yield component method — ears, kernel counts and a kernel-weight factor to bu/ac.
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How it's calculated
Bushels per acre = (ears/ac × kernel rows/ear × kernels/row) ÷ kernel-weight factor. Ears per acre comes from counting ears over a measured row length and scaling to a full acre by row spacing. The kernel-weight factor converts total kernels to bushels — it varies with kernel size, so it's really a stand-in for how favorable the season has been.
This is the classic Extension "yield component method." Count several representative spots (not just the best-looking row) and average — a single sample swings the estimate a lot. The kernel-weight factor is the biggest source of error: 90,000 is a reasonable long-run average, but drop it toward 75,000–80,000 in a favorable year with plump kernels, or push it up toward 100,000–105,000 after heat or drought stress during grain fill.
Row Wise estimates corn yield all season from satellite imagery and weather — field by field, updated every pass, no counting ears by hand.
Get notified at launch →Frequently asked questions
How do you estimate corn yield before harvest?
Count ears over a measured length of row (enough row to represent 1/1000 acre is traditional — 17.4 ft at 30-inch rows), then count kernel rows around and kernels down a row on a handful of representative ears and average them. Multiply ears/acre × kernel rows × kernels/row to get kernels per acre, then divide by a kernel-weight factor (about 90,000 kernels/bu on average) to get bushels per acre.
What kernel-weight factor should I use?
90,000 kernels per bushel is the standard average assumption. Use a lower number (75,000–85,000) in a favorable year with big, well-filled kernels, and a higher number (95,000–105,000) after heat or drought stress during grain fill shrinks kernel size — this is the single biggest lever on the estimate, so treat the result as a range, not an exact number.
How many spots should I sample?
At least 3–5 representative spots across the field, avoiding both the best and worst-looking areas, then average the ear counts and kernel counts. Corn yield varies a lot within a field, so one sample can be badly misleading.