Corn Yield Calculator

The corn yield calculator is a precision agriculture tool that estimates corn production in bushels per acre before harvest. Developed around the USDA Yield Component Method — also known as the ear count method — this calculator lets you predict yield weeks before the combine rolls, giving you time to plan marketing, storage, and equipment needs with confidence.

Whether you're a corn farmer in Iowa, an agronomist in Illinois, or a crop consultant serving multiple states, this tool provides fast, reliable, science-based yield estimates using just four field measurements: ear count, kernel rows per ear, kernels per row, and grain moisture content.

Our calculator is completely free, requires no sign-up, and works on any device — desktop, tablet, or smartphone. It's designed to be used in the field, with results calculated instantly as you enter your data.

The corn yield formula used by this calculator is the proven USDA Yield Component Method:

Yield (bu/acre) = (Ears per acre × Kernel rows per ear × Kernels per row) ÷ 90,000

The constant 90,000 represents the average number of kernels in one bushel of corn at 15.5% moisture. This number can vary slightly with kernel size — using 80,000-85,000 for large kernels and 95,000-105,000 for small kernels gives more accurate results in extreme cases.

Once you have your base yield, you adjust for actual grain moisture:

Moisture Factor = 1 + ((15.5 − Actual Moisture) ÷ 100)

Final adjusted yield = base yield × moisture factor. If your corn is wetter than 15.5%, the adjustment increases yield (since you're effectively drying it down). If drier, yield decreases slightly.

Step 1: Count Ears Per Acre

Measure 1/1000th of an acre. For 30-inch rows, that's 17 feet 5 inches. Count all harvestable ears (ears with at least some kernels) in that row section. Multiply by 1,000 to get ears per acre. For other row spacings: 1/1000 acre = 174.24 sq ft. Divide by your row spacing in feet.

Step 2: Sample 5 Representative Ears

From your sample row, pick 5 ears that look average — not the biggest, not the smallest. Break each ear in half (or use a knife) and count the number of kernel rows around the ear. Kernel row count is almost always an even number (14, 16, 18, or 20) because rows develop in pairs.

Step 3: Count Kernels Per Row

On each of the same 5 ears, count the kernels in a single row from base to tip. Don't count aborted or unfilled kernels at the very tip. Average the counts across all 5 ears.

Step 4: Measure Grain Moisture

Use a portable moisture tester on a handful of grain from your sample ears. If you don't have one, 15.5% (the standard) is a reasonable assumption for corn at black layer in normal conditions. Earlier in the season, moisture will be higher (25-35%).

Step 5: Enter Values and Calculate

Plug your four numbers into the calculator above. Click "Calculate" and you'll get an instant yield estimate in bushels per acre, plus a comparison against state and national averages.

Let's walk through a real-world example. Suppose you farm in central Iowa and take the following measurements in late August:

• Ears per acre: 32,000 (32 ears in 17'5" of 30" row)
• Kernel rows per ear: 16 (averaged across 5 ears)
• Kernels per row: 36 (averaged across 5 ears)
• Grain moisture: 22.5% (still drying down)

Step 1: Calculate total kernels per acre:
32,000 × 16 × 36 = 18,432,000 kernels per acre

Step 2: Divide by 90,000 to get base yield:
18,432,000 ÷ 90,000 = 204.8 bu/acre

Step 3: Apply moisture adjustment:
Factor = 1 + ((15.5 − 22.5) ÷ 100) = 1 + (−0.07) = 0.93
Adjusted yield = 204.8 × 0.93 = 190.5 bu/acre

Your estimated yield is approximately 190 bushels per acre at standard moisture — an above-average Iowa corn yield.