Corn Yield Calculator
Calculate corn yield per acre using ear count, kernel rows, and kernel weight data from your field.
Corn Yield Calculator
How to Use This Calculator
Count Ears per Acre
Walk 1/1000th of an acre in your field and count the number of harvestable ears. Multiply by 1000 to get ears per acre. Sample multiple locations for accuracy.
Measure Ear Characteristics
Select 5–10 representative ears and count the number of kernel rows around the cob and the number of kernels from butt to tip on one row.
Select Kernel Weight & Moisture
Choose a kernel weight factor based on expected grain fill (average is 85,000 kernels per bushel). Enter current grain moisture from a test or moisture meter.
Calculate and Interpret
Click Calculate to get estimated yield at current moisture and adjusted to the standard 15.5% moisture level used for commercial grain sales.
How We Calculate
The corn yield calculator uses the standard University Extension field-scouting formula: Yield (bu/acre) = [Ears/acre × Rows/ear × Kernels/row] ÷ Kernels/bushel. This method, developed and validated by Purdue University and Iowa State University Extension, is widely used by agronomists during the R4–R5 growth stage (dough to dent) to produce pre-harvest yield estimates that typically fall within 10–15% of actual combine yields.
Kernel weight (kernels per bushel) is the primary variable in the equation and reflects growing-season conditions. A drought-stressed crop may produce only 75,000–80,000 kernels per bushel, while a well-irrigated crop in optimal conditions can achieve 90,000–95,000 kernels per bushel. The default value of 85,000 represents average Corn Belt conditions. Moisture adjustment to the standard 15.5% moisture basis ensures apples-to-apples comparison across fields and years.
Field sampling accuracy improves with sample size. The University of Illinois recommends sampling at least 5 locations per field, avoiding end rows and obvious low-yield areas. Each location should represent a 1/1000th-acre segment (17.4 feet of 30-inch rows). Averaging results across multiple locations reduces the impact of within-field variability and produces estimates closely aligned with actual harvest data.
Sources & References
- Purdue University Extension — Estimating Corn Grain Yield Prior to Harvest (extension.purdue.edu)
- Iowa State University Extension — Pre-Harvest Corn Yield Estimates (extension.iastate.edu)
- USDA National Agricultural Statistics Service — Corn Yield Data (nass.usda.gov)
Data last verified:
Frequently Asked Questions
The field-scouting method typically estimates corn yield within 10–20% of actual combine yield when sampled correctly. Accuracy improves as you sample more locations per field (at least 5 recommended), as yield can vary significantly across a single field due to soil type, drainage, and pest pressure.
The most accurate estimates come at R5 (dent) stage when kernel weight is largely determined. Estimating at R4 (dough) stage is possible but introduces more uncertainty because grain fill is still occurring. Using it at R3 (milk) will significantly over-predict actual yield.
Ears per acre is the total number of harvestable corn ears in one acre. To estimate it, measure 1/1000th of an acre (17.4 feet in 30-inch rows, or 14.5 feet in 36-inch rows) and count all ears on both sides of the row. Multiply by 1,000 to get ears per acre.
The average Corn Belt kernel weight factor is approximately 85,000 kernels per bushel (a 56-lb bushel). Hot and dry seasons push this lower to 75,000–80,000 (lighter, shrunken kernels), while cool, wet seasons with excellent grain fill can produce heavier kernels at 88,000–95,000 per bushel.
Corn is traded at a standard 15.5% moisture basis. If your grain is at 20% moisture, it weighs more than 56 lbs per bushel due to extra water weight. Adjusting to 15.5% removes the water component so you are comparing true dry-grain yields, which is what you will be paid for at the elevator.
This calculator is designed for grain corn sold by the bushel. For silage, yield is typically expressed in tons of fresh or dry matter per acre and uses different metrics such as plant population, plant height, and ear size. A dedicated silage tonnage calculator would be more appropriate for that use case.
University Extension recommendations suggest sampling at least 5–10 locations per field for a reliable average. Large fields (over 80 acres) with variable soils benefit from 10 or more samples. Avoid sampling near field edges, waterways, or areas with obvious pest or disease damage as these can skew your average.
The U.S. national average corn yield is approximately 177–181 bushels per acre (2022–2024 USDA data). Top Corn Belt states like Iowa, Illinois, and Indiana frequently average 200+ bu/acre. High-yield contest winners can exceed 300 bu/acre under optimal management, while dryland fields in drier regions may average 100–130 bu/acre.
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