Corn Yield Calculator
Estimate corn yield in bushels per acre using the kernel count method or ear weight method. Includes moisture adjustment and US yield benchmarks.
Count ears and kernels in a 1/1000 acre sample to estimate yield.
Kernel Count Inputs
Walk 17.4 ft for 1/1000 acre count
Count all harvestable ears in the measured length
Count rows x kernels per row on 3-5 ears, then average
Standard = 15.5% (market weight)
Estimated Yield
US Yield Benchmarks
Row Spacing - Length for 1/1000 Acre Count
| Row Spacing | Walk This Length | Count Method |
|---|---|---|
| 20 inch rows | 26.2 ft | High-density corn production |
| 30 inch rows | 17.4 ft | Most common US row width |
| 36 inch rows | 14.5 ft | Wide-row production |
| 38 inch rows | 13.1 ft | Southern US, dual-crop systems |
| 40 inch rows | 13.1 ft | Wide-row corn-soybean systems |
Count all harvestable ears along this measured length to represent a 1/1000-acre sample.
Moisture Adjustment Reference
| Harvest Moisture | Adjustment Factor | Effect |
|---|---|---|
| 30% | 0.818 | Raw count overstates yield by 22% |
| 25% | 0.863 | Raw count overstates yield by 16% |
| 20% | 0.911 | Raw count overstates yield by 10% |
| 17% | 0.940 | Raw count overstates yield by 6% |
| 15.5% | 1.000 | Standard basis - no adjustment needed |
| 14% | 1.018 | Slightly dry - adjusted is slightly higher |
Estimating Corn Yield Before Harvest
Pre-harvest yield estimation is a valuable practice for farm planning, grain marketing decisions, and crop insurance documentation. Knowing your likely yield 3-6 weeks before harvest gives you time to secure favorable grain contracts, arrange adequate storage, and plan logistics. The kernel count method developed by University Extension programs provides a reasonably accurate estimate using simple field measurements.
The kernel count method relies on the fact that corn yield is essentially the product of three factors: plant population (ears per acre), kernel set per ear, and kernel weight. At the R5 dent stage, kernel count is fully determined and kernel weight is close to its final value. By sampling multiple field locations, you get a statistically representative snapshot of the field's likely performance.
Sampling Strategy for Accuracy
The biggest source of error in yield estimation is insufficient sampling. A single sampling location may hit an unusually high or low spot in the field. Best practice is to sample 5-10 locations randomly distributed across the field, avoiding field edges, low spots, and areas near field entrances. Average the ear counts and kernel counts from all locations before applying the formula.
For kernel counting, select 3-5 representative ears from each sampling location - not the biggest or smallest, but the most typical for that area. Count the kernel rows around the cob and the kernels in one complete row from base to tip. Multiply these two numbers and subtract any missing or unfilled kernels at the very tip. Average across the sampled ears.
Understanding Moisture Adjustment
Corn grain is priced and measured at 15.5% moisture (the industry standard). When you harvest at higher moisture content, the extra water weight inflates your raw bushel count. The moisture adjustment formula corrects this: multiply your raw estimate by (100 - harvest moisture) / 84.5 (since 100 - 15.5 = 84.5). If you harvest at 25% moisture, your adjustment factor is (100-25)/84.5 = 0.887, meaning adjusted yield is about 11% less than the raw count.