Corn Yield Calculator
Estimate your corn crop before harvest using the standard 1/1000-acre sampling method developed at the University of Illinois. Enter the number of ears, kernels per ear, and kernel size from a representative sample, then add your field area to see total bushels. Toggle the profit panel to factor in corn price and moisture content.
Formula
Worked example
A farmer counts 32 ears in a 1/1000-acre section of 30-inch rows (17.4 ft). The average ear has 560 kernels. Using medium kernel size (90,000 per bushel): (560 x 32 x 1000) / 90,000 = 17,920,000 / 90,000 = 199 bu/acre. On a 100-acre field that is 19,900 bushels total.
How the 1/1000-acre sampling method works
The standard pre-harvest corn yield estimate starts with a 1/1000-acre field sample, a technique developed by the University of Illinois and adopted across North American extension programs. For 30-inch row spacing, one sample is a 17.4-foot section of a single row. Count every harvestable ear in that section, then count the kernel rows on one ear and the kernels in one representative row on each of five ears, multiply those two numbers to get kernels per ear, and average across the five ears. Repeat in at least three, ideally five, locations spread across the field and average all the counts together. Plug those averages into the formula above and the calculator converts them to bushels per acre using the standard kernel weight for the size you observed. The approach is fast, requires no special equipment, and delivers an estimate accurate to within roughly 10-15% when sampled correctly.
Why kernel size matters
Kernel weight is the most variable factor in the formula. The calculator uses three standard classes: small (120,000 kernels per 56-lb bushel), medium (90,000), and large (80,000). Under drought or late-season stress, kernels are lighter and smaller, so the same kernel count produces fewer bushels; the opposite is true in ideal filling conditions. If you are unsure, choose Medium, which represents a reasonable long-run average for most hybrids under normal conditions. Remember that kernel size class affects the yield estimate by up to 50%, so choosing the right category matters as much as counting carefully.
Moisture adjustment and drying shrink
Corn is traded at 15.5% moisture content, the standard that defines a 56-pound bushel in the US. If you harvest at a higher moisture - common when you want to capture a premium hybrid or lock in a contract date - those extra pounds of water are subtracted at the elevator, and your bushel count shrinks. The moisture adjustment factor is (100 - harvest moisture) divided by (100 - 15.5). Harvesting at 18% moisture, for example, yields about 97% of the number of dry-equivalent bushels the field actually produces. Enable the profit panel to see the dry-equivalent yield and factor drying cost into your return.
Estimating profitability before harvest
The profit panel turns the yield estimate into a rough financial projection. Enter the corn price you expect to receive (either a forward contract price or your current futures reference) and your variable input cost per acre, which typically includes seed, fertilizer, herbicide, fungicide, and custom application charges. Gross revenue is the total dry-equivalent bushels times the price; net profit is gross revenue minus total input cost. This is a variable-cost-only estimate: it does not include land rent, machinery depreciation, or overhead, so treat it as a contribution margin rather than a true profit figure. Pair it with a full enterprise budget from your local extension office for a complete picture.
US corn yield benchmarks by performance tier
| Yield tier | Bu/acre | T/ha | Context |
|---|---|---|---|
| Below average | < 100 | < 6.3 | Drought, disease, or severe stand loss |
| Average | 100-150 | 6.3-9.4 | Typical dryland production, stress years |
| Good | 150-200 | 9.4-12.6 | Irrigated or favorable dryland year |
| Excellent | 200-250 | 12.6-15.7 | Top management + ideal conditions |
| Record-class | > 250 | > 15.7 | Elite hybrids, optimal inputs, contest fields |
Based on USDA NASS data and university extension research. US national average was approximately 177 bu/acre in 2023.
Frequently asked questions
How accurate is the 1/1000-acre corn yield estimate?
When you sample at least three to five representative locations per field and count carefully, the method typically comes within 10-15% of actual harvest yield. Accuracy drops if you sample too close to field edges, skip areas that look different from the rest, or count ears damaged by disease or lodging. Weather between estimation and harvest can also shift the result, especially if a late-season drought cuts kernel fill.
How long is a 1/1000-acre row for different row spacings?
The section length depends on your row width: 30-inch rows need 17.4 feet, 28-inch rows need 18.7 feet, 32-inch rows need 16.3 feet, 36-inch rows need 14.5 feet, 38-inch rows need 13.7 feet, and 40-inch rows need 13.1 feet. Measure from a start point, count every harvestable ear in that section, and repeat in multiple field locations.
How do I count kernels per ear?
Pick a representative ear from the middle of the sample section. Count the number of kernel rows running along the length of the ear (typically 14-20 rows). Then count the kernels along one row from tip to butt, excluding any poorly filled tip kernels. Multiply rows by kernels per row to get kernels per ear. Repeat on at least five ears per sample location and average the results to reduce variability.
What is the world average corn yield?
The world average is roughly 85 bushels per acre (5.3 tonnes per hectare), but this hides wide variation. The US national average was about 177 bu/acre in 2023, Iowa and Illinois frequently top 200 bu/acre in good years, and top contest growers have exceeded 500 bu/acre under optimized conditions. Developing regions average far below the US benchmark due to input access, variety, and irrigation differences.
When is the best time to do a pre-harvest yield estimate?
The most reliable time is when kernels have reached black layer, the stage of physiological maturity, typically at around 30-35% moisture. At that point the kernel count and dry weight are fixed and only moisture will change before harvest. Estimating earlier, during grain fill, is possible but riskier because late stress can reduce both kernel number and weight.
Can I use this calculator for sweet corn or silage corn?
This calculator is designed for field corn (dent corn) marketed as grain. Sweet corn is harvested immature, making kernel-count estimates unreliable. Silage yield is measured in tons of wet biomass per acre, not bushels per ear, and requires a different sampling approach based on plant height, stalk diameter, and whole-plant weight.
How does moisture content affect how many bushels I get paid for?
Corn traded at any moisture above 15.5% is discounted because the extra water adds weight but not value. The elevator applies a shrink factor equal to (100 - delivery moisture) divided by (100 - 15.5). For example, if you deliver at 20% moisture, each physical bushel pays for only (80/84.5) = 94.7% of a standard bushel. Drying costs also reduce net return; factor both into your harvest timing decision.