Corn Yield Calculator (Bushels Per Acre)

A corn yield calculator helps estimate bushels per acre (BPA) before harvest by counting ears and kernels in representative areas of a field. While final yield is determined at the elevator, an early yield estimate is useful for marketing decisions, harvest planning, and comparing hybrids or management zones.

This guide explains the common corn yield estimation method, shows the formula, and includes practical examples you can replicate in the field.

What You Need to Estimate Corn Yield

Most field yield estimates use these measurements:

Ears per 1/1000 acre (ear count from a measured row length)
Kernel rows around the ear
Kernels per row
Adjustment factor for kernel weight and conditions (often 80,000–95,000)

Tip: Take multiple samples across the field and average them. Avoid headlands and abnormal spots unless you’re estimating those zones specifically.

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The Common Corn Yield Formula (90,000 Method)

A widely used approach estimates yield using kernels per acre divided by an adjustment factor.

Step 1: Kernels per ear = (Rows around ear) × (Kernels per row)

Step 2: Kernels per acre = (Ears per 1/1000 acre) × (Kernels per ear) × 1,000

Step 3: Estimated BPA = (Kernels per acre) ÷ (Adjustment Factor)

The “90,000 method” refers to using 90,000 kernels per bushel as a typical adjustment factor under average conditions.

Estimated BPA = (Ears per 1/1000 acre × Kernels per ear × 1,000) ÷ 90,000

The adjustment factor accounts for kernel size, test weight, and growing conditions. In excellent conditions, some use 80,000–85,000. In stressed conditions, 95,000–100,000 may be more realistic.

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How to Measure 1/1000 Acre of Row

To count ears in 1/1000 acre, you need a specific row length based on row spacing.

Row length for 1/1000 acre = 43.56 sq ft ÷ (Row spacing in feet)

Common row lengths:

30-inch rows (2.5 ft): 17.4 ft
20-inch rows (1.67 ft): 26.1 ft
15-inch rows (1.25 ft): 34.8 ft

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Example Corn Yield Estimate

Sample data:

Row spacing: 30 inches
Ears counted in 17.4 ft of row: 30 ears
Rows around ear: 16
Kernels per row: 35
Adjustment factor: 90,000

Step 1: Kernels per ear:

16 × 35 = 560 kernels per ear

Step 2: Kernels per acre:

30 × 560 × 1,000 = 16,800,000 kernels per acre

Step 3: Estimated bushels per acre:

16,800,000 ÷ 90,000 = 186.7 BPA

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Why Corn Yield Estimates Can Be Off

Field estimates are useful, but final yield can differ due to:

Kernel depth and fill (not fully captured by kernel counts)
Harvest losses (ear drop, header loss)
Moisture variation and test weight
Sampling bias (too few locations or “nice spots” only)

Best practice: sample 5–10 spots per field (or per management zone) and average the results.

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Use Our Free Corn Yield Calculator

Skip the manual math and estimate BPA instantly:

Open the Free Corn Yield Calculator

Fast field estimates using ear counts and kernel counts.

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Frequently Asked Questions

What adjustment factor should I use?

90,000 is common for average conditions. If kernels are deep and conditions are excellent, a lower factor (80,000–85,000) may fit. In stress or lighter kernels, higher factors (95,000–100,000) may be more realistic.

Is the corn yield estimate method accurate?

It’s an estimate. It’s best used for comparing fields or zones and getting a directional number for planning—not as a guarantee of final harvested yield.

How many samples should I take?

At least 5 per field, and more if the field has variability. Average your results for a more reliable estimate.

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