# What will my corn yield be?

Estimates corn grain yield in bushels per acre before harvest by the yield component method: ears in a length of row, kernel rows and kernels per row, and a kernel weight factor, with tonnes per hectare.

- Page: https://www.acalculator.org/biology/corn-yield-calculator
- JSON spec: https://www.acalculator.org/biology/corn-yield-calculator.json
- Version: eb2b15dd0f65

## Default answer

Example with the default inputs (Row width 30 in, Harvestable ears in that length 30, Kernel rows per ear 16, Kernels per row 32, Kernel weight factor 85): Your corn should yield about 180.7 bushels per acre.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| w | Row width | The distance between the centres of two rows. |
| len | Length of row counted | The length of row in which you counted the ears. Leave empty to use 1/1000 acre (17.4 ft at 30-inch rows). |
| ears | Harvestable ears in that length | The number of ears that will be harvested, in the length counted; an average of several rows works. |
| rows | Kernel rows per ear | The average number of kernel rows around each ear (usually an even number from 12 to 20). |
| k | Kernels per row | The average number of kernels along each row, not counting the small kernels at the tip. |
| f | Kernel weight factor | Thousands of kernels per bushel: 65, 75 or 85 for normal grain fill, 90 to 100 after a stressful season. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| yield | Estimated yield | Ears per acre × kernels per ear ÷ (kernel weight factor × 1,000), in bushels per acre. |
| tonnes | Estimated yield (metric) | The yield in tonnes per hectare, at 56 lb of shelled corn per bushel. |
| earsPerAcre | Ears per acre | The ears counted ÷ the area of row counted (length × row width), per acre. |
| kernelsPerEar | Kernels per ear | Kernel rows per ear × kernels per row. |
| rowLength | Row length for 1/1000 acre | The length of row at this row width that covers 1/1000 acre. |

## Method

Bushels per acre = ears per acre × (kernel rows × kernels per row) ÷ (kernel weight factor × 1,000); ears per acre = ears counted × 43,560 ft² ÷ (row length × row width).

## Assumptions

- The kernel weight factor stands for kernel size: 65 for heavy kernels, 85 for light ones, 90 to 100 after a stressful grain fill.
- Purdue says the method is probably only accurate within about 20 bushels per acre; count several spots in the field.
- Tonnes per hectare use the 56 lb bushel of shelled corn.

## Worked examples

1. w = 0.762, ears = 30, rows = 16, k = 31.9375, f = 75 gives yield = 204.4, earsPerAcre = 30,000, kernelsPerEar = 511, tonnes = 12.829711. Source: Nielsen RL, Estimating Corn Grain Yield Prior to Harvest, Purdue University Corny News Network, August 2021 (bushels per acre = ears per acre × average kernels per ear ÷ a kernel weight factor in thousands; 17.4 ft of 30-inch row is 1/1000 acre; factors of 65, 75 and 85, or 90 to 100 under stress; 30 ears and 511 kernels per ear give 236, 204 and 180 bu/ac), https://www.agry.purdue.edu/ext/corn/news/timeless/yldestmethod.html (retrieved 2026-10-03); Iowa State University Extension, Ag Decision Maker C6-80, Metric Conversions (corn with a 56-pound bushel: 1 bushel per acre = 0.0628 metric tons per hectare), https://www.extension.iastate.edu/AGDm/wholefarm/html/c6-80.html (retrieved 2026-10-03).
2. w = 0.762, ears = 30, rows = 16, k = 31.9375, f = 85 gives yield = 180.352941, rowLength = 5.310835. Source: Nielsen RL, Estimating Corn Grain Yield Prior to Harvest, Purdue University Corny News Network, August 2021 (bushels per acre = ears per acre × average kernels per ear ÷ a kernel weight factor in thousands; 17.4 ft of 30-inch row is 1/1000 acre; factors of 65, 75 and 85, or 90 to 100 under stress; 30 ears and 511 kernels per ear give 236, 204 and 180 bu/ac), https://www.agry.purdue.edu/ext/corn/news/timeless/yldestmethod.html (retrieved 2026-10-03).
3. w = 0.9144, len = 6.096, ears = 25, rows = 16, k = 30, f = 85 gives earsPerAcre = 18,150, yield = 102.494118, tonnes = 6.433316. Source: Nielsen RL, Estimating Corn Grain Yield Prior to Harvest, Purdue University Corny News Network, August 2021 (bushels per acre = ears per acre × average kernels per ear ÷ a kernel weight factor in thousands; 17.4 ft of 30-inch row is 1/1000 acre; factors of 65, 75 and 85, or 90 to 100 under stress; 30 ears and 511 kernels per ear give 236, 204 and 180 bu/ac), https://www.agry.purdue.edu/ext/corn/news/timeless/yldestmethod.html (retrieved 2026-10-03); Iowa State University Extension, Ag Decision Maker C6-80, Metric Conversions (corn with a 56-pound bushel: 1 bushel per acre = 0.0628 metric tons per hectare), https://www.extension.iastate.edu/AGDm/wholefarm/html/c6-80.html (retrieved 2026-10-03).

## FAQ

### How do I estimate corn yield before harvest?

Count the harvestable ears in 1/1000 acre of row (17.4 ft of 30-inch rows). On every fifth ear in the row, count the kernel rows and the kernels per row. Then bushels per acre = ears per acre × kernels per ear ÷ (kernel weight factor × 1,000).

### What kernel weight factor should I use?

Purdue’s Bob Nielsen suggests working out the yield with factors of 65, 75 and 85 in a normal season; a lower factor means heavier kernels and a higher yield. After a stressful grain fill, use 90 to 100. The default here is 85, the cautious end of the normal range.

### How long a row is 1/1000 acre?

Divide 43,560 sq ft by the row width in feet, then by 1,000. For 30-inch rows that is 43,560 ÷ 2.5 ÷ 1,000 = 17.4 ft; for 36-inch rows, 14.5 ft; for 20-inch rows, 26.1 ft. Leave the length empty and the calculator uses this length.

### How accurate is the estimate?

Purdue says it is probably accurate only within about 20 bushels per acre, mostly because kernel weight is a guess until the grain is mature. Count several spots that stand for the whole field and average them.

### Which kernels should I count?

Purdue says to leave out the extreme butt and tip kernels: start and end where there are complete rings of kernels around the cob, and do not count aborted kernels. If the row number changes along a pinched ear, use an average.

### How do bushels per acre convert to tonnes per hectare?

A bushel of shelled corn weighs 56 lb, so 1 bu/ac is about 0.0628 t/ha. 200 bu/ac is about 12.55 t/ha.

## Sources

- Nielsen RL, Estimating Corn Grain Yield Prior to Harvest, Purdue University Corny News Network, August 2021 (the yield component method; 17.4 ft of 30-inch row is 1/1000 acre; fudge factors 65, 75 and 85, or 90 to 100 under stress; 30 ears and 511 kernels per ear give 236, 204 and 180 bu/ac; accurate within about 20 bu/ac). https://www.agry.purdue.edu/ext/corn/news/timeless/yldestmethod.html (retrieved 2026-10-03)
- Iowa State University Extension, Ag Decision Maker C6-80, Metric Conversions (corn with a 56-pound bushel: 1 bushel per acre = 0.0628 metric tons per hectare). https://www.extension.iastate.edu/AGDm/wholefarm/html/c6-80.html (retrieved 2026-10-03)