Agrimetra

Corn yield calculator

Thirty ears counted along 17.4 ft of a 30-inch row — a thousandth of an acre — averaging 16 kernel rows and 38 kernels to the row works out at 202.7 bu/ac, or 12.72 t/ha, from 30,000 ears per acre. Kernel weight is the honest uncertainty in this method: the same count comes to 243 bu/ac if the grain fills well and 174 bu/ac if the season turns hot and dry, which is why the page prints the band and not a single promise.

The answer updates as you type — there is no button to press.

No fields saved yet — measure one and save it below.

ac

e.g. 80 ac — for the whole-field totals on the job sheet.

in

e.g. 30 inches — the calculator tells you how far to walk.

Walk the row length shown below and count harvestable ears — e.g. 32.

Average of a few ears — e.g. 16.

Count one row, ignore the tip — e.g. 35.

Your answer

Estimated yield199.1 bu/ac

In tonnes per hectare
12.5 t/ha
Ears per acre
32,000
Row length to count along
17.4 ft (5.3 m)
The same field in a good, a typical and a poor season
239 / 199 / 171 bu/ac

Field job sheet

Type the field area above (or pick a saved field) to get the whole-field total, the last bag and a sheet to print or send.

How the answer is worked out

The yield-component method multiplies four counts and divides by one assumption:

ears per acre × kernel rows per ear × kernels per row ÷ kernels per bushel

Why the band is the answer

A single figure from this method implies a precision it does not have. Ears and kernels can be counted; kernel weight cannot be, until the combine goes through the field. Printing the same count against a good, a typical and a poor filling season shows the width of the real answer — in the example above, a spread of nearly 70 bu/ac on identical counts. Plan marketing and storage against the band, not against its middle.

Sampling beats precision

Three things move this estimate more than any arithmetic:

  1. Where you count. Headlands, end rows, a wet hole and a hill are not the field. Sample in representative places and count several sites.
  2. What counts as harvestable. Barren and nubbin ears are part of the stand and a part of the yield they do not contribute to; count them as they are.
  3. How many sites you average. Variability between sites is usually larger than the difference between two kernel weight assumptions.

Save the field above and the sheet turns the estimate into total bushels for that field, which is the figure that decides whether the bin has room.

A worked example

Every figure below is computed by the calculator above from this case — nothing here is typed in by hand:

Row spacing
30
Ears counted in 1/1000 acre
30
Kernel rows around an ear
16
Kernels along the ear
38
How the season has gone
Typical season

Estimated yield:202.7 bu/ac

In tonnes per hectare
12.72 t/ha
Ears per acre
30,000
Row length to count along
17.4 ft (5.3 m)
The same field in a good, a typical and a poor season
243 / 203 / 174 bu/ac

Worked by Agrimetra with the same engine the calculator above runs.

What this means in the United States

The yield-component estimate is what growers walk the field with before harvest: ears per acre, rows per ear, kernels per row, divided by a kernel-weight factor. The factor is the honest uncertainty — 90,000 kernels per bushel is the common default and a season with light kernels sits well above it.

Questions growers actually ask

How do I count a thousandth of an acre?
Measure the row length the calculator gives for your row spacing and count every harvestable ear along it — 17 ft 5 in in 30-inch rows, 26 ft 2 in in 20-inch rows. Do it in several places across the field and average them; one sample is a guess, five or six is an estimate.
What is the kernel weight factor?
Kernels per bushel. It is the one term you cannot count, so it is offered as three seasons rather than a number to type: about 75,000 when filling weather is good and kernels are big, 90,000 in a typical year, 105,000 when heat or drought during grain fill leaves them light.
When in the season is this estimate worth making?
Once the kernels are set — after pollination and blister stage — the ear and kernel counts stop changing and only kernel weight is still moving. Earlier than that you are counting potential, not grain. That is also why the band matters more than the headline: the remaining uncertainty is entirely in the weight.
How is the tonnes per hectare figure derived?
A bushel of corn is 56 lb by market convention at 15.5 % moisture, so bushels per acre × 56 lb, converted to kilograms and spread over a hectare instead of an acre, gives t/ha. It is the same estimate in the other trading system, not a second calculation.

Last updated:

Sources

Calculators that use the same field