Pre-Harvest Field Estimation
Soybean & Corn
Yield Calculator
Estimate yield from field counts at R5–R6 (corn) or R6–R7 (soybeans) — the same ear-count and kernel-count math crop tour scouts run in August. Pod-count method for soybeans. Sample at least 3 locations per field for reliable estimates. Then see what the trade expects the national number to be.
Method: Yield Component Method (ears × kernel rows × kernels per row ÷ 90, for a 1/1000-acre sample; widely referenced across US Corn Belt extension services).
Accuracy: corn estimates run about ±20 bu/ac — the figure Purdue, Iowa State, Ohio State and Penn State Extension all give for this method. Sample at least 5 locations, 10 ears each, and estimate at the milk (R3) stage or later. Soybean estimates are looser still; Michigan State puts them at ±25% or worse before R6.
Not a substitute for certified yield monitoring or combine data.
Corn Yield Estimator
Ear Count Method Quick Fill — Start from a Typical Scenario
Select a scenario to auto-fill inputs:
Step 1 — Count Ears
Sets 1/1000-acre row length
Row length: 17'5" · typical 28–36 ears
Step 2 — Count Kernels (5 Representative Ears)
Count around circumference
Count from base to tip
Test weight does not enter this estimate. The ear-count method uses only ears, rows and kernels.
Formula Used
Yield (bu/ac) = (ears × kernel rows × kernels/row) ÷ 90
Ear count × 1000 = plants/acre (1/1000 acre row method). The 90,000 kernels/bu constant is the long-standing default (Iowa State); Some extension guides use a lower figure for modern hybrids, so the range above sweeps 65,000–95,000. Valid from the milk (R3) stage on. Test weight is not part of the formula. The yield range above only shows what changes if kernels per bushel are 65,000 to 95,000 instead of 90,000. It is not the field error. Worked example: 32 ears × 16 rows × 35 kernels ÷ 90 = 199 bu/ac.
Ear count × 1000 = plants/acre (1/1000 acre row method). The 90,000 kernels/bu constant is the long-standing default (Iowa State); Some extension guides use a lower figure for modern hybrids, so the range above sweeps 65,000–95,000. Valid from the milk (R3) stage on. Test weight is not part of the formula. The yield range above only shows what changes if kernels per bushel are 65,000 to 95,000 instead of 90,000. It is not the field error. Worked example: 32 ears × 16 rows × 35 kernels ÷ 90 = 199 bu/ac.
Field Sampling Best Practices
• Sample at least 3 locations per field, at least 200 feet apart and away from field edges.
• Avoid sampling spots you noticed from the road — select locations before walking the field.
• Count ear length in the designated 1/1000-acre row length for your row width (see table in Fast Facts → Crop Removal tab).
• Count kernel rows and kernels/row on 5 representative ears per location — not the biggest or smallest.
• Test weight does not change this estimate. Weigh it at harvest, because low test weight docks grain value.
• Average multiple locations — field variability of 30–50 bu/ac between zones is common.
• Avoid sampling spots you noticed from the road — select locations before walking the field.
• Count ear length in the designated 1/1000-acre row length for your row width (see table in Fast Facts → Crop Removal tab).
• Count kernel rows and kernels/row on 5 representative ears per location — not the biggest or smallest.
• Test weight does not change this estimate. Weigh it at harvest, because low test weight docks grain value.
• Average multiple locations — field variability of 30–50 bu/ac between zones is common.
Common questions
How do I estimate corn yield before harvest?
The ear count method: count ears in 1/1000 acre row length, then count kernel rows and kernels per row on 5 representative ears. Formula: ears × kernel rows × kernels per row / 90, for a 1/1000-acre sample. Kernel weight varies, so the estimator shows a range across 65,000–95,000 kernels per bushel. Enter these counts in the AGSIST Yield Estimator for an instant field estimate.
How accurate is the pre-harvest yield estimate?
The yield component method is accurate to roughly plus or minus 20 bushels per acre — a figure commonly cited in extension guides. Accuracy improves if you sample at least 5 locations and 10 ears per location, and estimate at the milk (R3) stage or later. Because kernel weight varies, the estimator also shows a range built from 65,000 to 95,000 kernels per bushel.
How do I estimate soybean yield before harvest?
Count plants per acre, then count pods per plant and seeds per pod on 10 representative plants. Formula: plants/ac × pods/plant × seeds/pod / (seeds/lb × 60). The AGSIST estimator calculates this automatically.
Disclaimer: Pre-harvest yield estimates are informational only. Corn carries roughly ±20 bu/ac of uncertainty and soybeans ±25% or more, even with good sampling. Not a substitute for certified yield monitoring, combine data, or professional agronomic advice. Verify marketing, insurance, and input decisions with your CCA, crop insurance agent, and grain merchandiser. Not financial, agronomic, or legal advice.
Method: Yield Component Method · Referenced by
University of Wisconsin-Extension, University of Minnesota Extension, and Iowa State University Extension ·
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