From a row to a field question
What does this patch say about the corn crop?
A few good-looking ears can make a field seem promising. The useful question is more exact: how much grain do those ears represent over the ground they came from? If you have already harvested a small area, its shelled grain weight is a better starting point, but that weight changes with moisture.
This calculator keeps those two checks separate. Select US units for bushels per acre or Metric for tonnes per hectare, both on a 15.5% grain-moisture basis. Neither result is a guarantee for the whole field.
How to use the calculator
Choose the evidence you have
Select Count ears before harvest or Weigh grain when you have shelled a measured sample. Set US or metric units. Changing units converts valid entries.
Match the sample to its area
For ears, count a single row strip and enter its length, row spacing and average kernels per ear. For grain, enter shelled-grain weight, the exact area harvested and measured moisture. The measured area must be the area that produced that count or weight.
Read the yield, then judge the field
Select Calculate corn yield. The large result is bu/ac with US units or t/ha with Metric. The sample area and optional field projection follow the same choice. Open the optional section for a justified kernel-size assumption or a whole-field projection. Repeat the calculation at several representative spots before using a projected total.
What the ear count can tell you
Imagine 28 harvestable ears along 17.424 ft of one row with 30 in row spacing. That strip covers exactly 43.56 sq ft, or one-thousandth of an acre. Suppose sampled ears average 560 kernels each, perhaps 16 kernel rows with 35 kernels in each row.
That last step is an estimate. The default 90,000 kernels per bushel is a common planning factor, not a property of every hybrid or season. Heavier kernels mean fewer kernels make a 56-lb bushel, and estimated yield rises. Small kernels push it down. Count more than one part of the field rather than selecting only the best ears.
Check the formula behind the ear estimate
The row length and spacing turn a count into ears per acre. The kernel count turns ears into a grain quantity. These steps are visible so you can spot a misplaced decimal or a row spacing entered in the wrong unit.
Sample acres = row length × row spacing ÷ area of one acre
Ears per acre = sampled ears ÷ sample acres
Estimated bu/ac = ears per acre × average kernels per ear ÷ kernels per bushel
Use feet with feet or metres with metres in the area formula; the calculator converts inches or centimetres first. The 17.424 ft example gives 28,000 ears/ac. At 560 kernels per ear and 90,000 kernels/bu, that is 174.22 bu/ac, or about 10.94 t/ha.
Do not apply a moisture correction to this ear count. No grain mass was measured, so there is no observed water weight to remove. A later weighed sample can replace the estimate.
When you have a weighed grain sample
After harvest, shell the corn from a measured patch and weigh grain without cobs. Suppose the grain weighs 100 lb, covers 0.01 acre and tests at 20% moisture. To compare it with standard corn grain, keep its dry matter and express that same dry matter at 15.5% moisture.
Weight at 15.5% = measured grain weight × (100 − measured moisture %) ÷ 84.5
bu/ac = adjusted weight in lb ÷ 56 ÷ sampled acres
Here, 100 × 80 ÷ 84.5 = 94.67 lb at 15.5%. Divide by 56 and then by 0.01 acre: 169.06 bu/ac, or about 10.61 t/ha. The difference from the ear example does not mean one field lost exactly 5.16 bu/ac. They are separate illustrative samples with different evidence.
Moisture changes weight, not dry matter
Think of two bags with the same dry kernels. The wetter bag includes more water and weighs more. Comparing the bags as harvested would make wetter grain seem to yield more. The 15.5% adjustment levels that comparison.
If measured moisture is below 15.5%, the equivalent standard-basis weight can be higher than the actual scale weight. That is a mathematical comparison, not new grain. The tool does not predict the physical dried weight you can sell under a particular elevator policy, mechanical drying loss, handling shrink or price discount.
Use wet-basis grain moisture from the same shelled sample you weighed. Do not enter whole ears, stover or a bin-volume estimate as sample grain weight.
How far can one sample travel?
The optional field-area result applies the sampled yield to a larger block. In the ear example, 174.22 bu/ac across 10 acres projects about 1,742.22 bushels, or 44.25 tonnes. That multiplication is easy; deciding whether the sample represents all 10 acres is harder.
Suppose three spots indicate 150, 174 and 190 bu/ac. Keep that 150–190 range beside the location of each sample. The 190-bushel spot is useful evidence, but it is not a field-wide promise. An average only helps when your sampling plan represents the area you want to summarize.
Walk beyond the convenient field edge. Include stronger and weaker areas in a deliberate sampling plan, and keep each sample's area and moisture with its result. The Corn Planting Calculator helps plan stand density, but planted seed count is not a harvested ear count.
Before using this number in a crop plan
Five quick checks
- Was the ear strip or harvested patch measured, not guessed?
- Did the count include only ears likely to reach harvest?
- Were kernels per ear averaged across representative ears?
- Was the grain sample shelled and its moisture actually measured?
- Does the whole-field projection cover ground similar to the sample?
Small samples, uneven emergence, lodging and harvest losses can all separate this estimate from a final scale ticket. The Yield per Hectare and Acre Calculator can standardize a completed harvest by area. Use a measured final yield and actual sale terms when planning income with the Farm Profit Calculator.