Corn Moisture Calculator
Adjust wet corn yield to standard 15.5% moisture. Calculate shrink percentage and accurately convert field yield to marketable bushels.
Moisture Adjustment Inputs
Convert wet yield to standard moisture
Yield at field moisture
Measured grain moisture
US standard: 15.5%
Take multiple samples from different field locations and average them for the most accurate results. Avoid border rows and unusual spots.
All calculations use USDA-standard formulas. No registration required, works on mobile, tablet, and desktop.
What Is a Corn Moisture Calculator?
A corn moisture calculator converts wet-weight corn yield to the standard 15.5% moisture basis used for grain marketing, USDA reporting, and yield comparisons. Because corn is bought and sold at standard moisture, knowing how to adjust your field yield to standard moisture is essential for accurate record-keeping and fair grain transactions.
When you harvest corn at 25% moisture, you're hauling water along with grain. A 200-bushel wet yield at 25% becomes about 181 bushels at 15.5% moisture — a 9.5% shrink. This calculator handles that math instantly.
The same calculation applies to other grains: wheat standard is 13.5%, soybeans 13%, sorghum 14%. Just change the standard moisture value in the calculator.
Corn Moisture Adjustment Formula
The moisture adjustment formula is based on the dry matter content of grain:
Adjusted Yield = Wet Yield × (100 − Actual Moisture) ÷ (100 − Standard Moisture)
This works because dry matter is conserved. If you have 100 lb of grain at 25% moisture, that's 75 lb dry matter. At 15.5% moisture, those 75 lb of dry matter weigh 88.76 lb total (75 ÷ 0.845).
Example
You harvest 220 bu/ac at 22.5% moisture. Adjusting to 15.5% standard:
220 × (100 − 22.5) ÷ (100 − 15.5) = 220 × 77.5 ÷ 84.5 = 201.8 bu/ac
So your 220 wet bushels shrink to about 202 standard bushels — an 8.3% shrink.
Why 15.5% Moisture for Corn?
The 15.5% moisture standard for corn was established by the USDA decades ago and represents the equilibrium moisture content of corn stored at moderate temperature and humidity. Below 15.5%, corn is safe for long-term storage. Above 15.5%, mold and insect activity increase, and corn must be dried before storage.
Other grains have different standards because of differences in oil content, kernel structure, and storage characteristics:
- Corn: 15.5% moisture
- Soybeans: 13.0% moisture
- Wheat: 13.5% moisture
- Grain sorghum: 14.0% moisture
- Oats: 14.0% moisture
- Barley: 14.5% moisture
Harvest Moisture & Drying Costs
Harvesting at higher moisture and drying grain is sometimes economically preferable to waiting for field dry-down:
Drying Cost
Each point of moisture removed costs about 2-3 cents per bushel in propane/electricity. Drying 25% to 15.5% = ~$0.20/bu.
Field Loss
Waiting to dry in field risks lodging, ear drop, and storm damage. Each week past maturity loses 0.5-2 bu/ac.
Mold & Mycotoxins
Wet corn in field attracts insects and develops molds. Aflatoxin risk increases dramatically above 22% moisture.
Test Weight
Corn harvested at 22-25% and dried gently often has higher test weight than corn left to field-dry.
Frequently Asked Questions
Everything you need to know about corn yield calculation
The USDA standard moisture content for corn is 15.5%. All grain transactions, yield reports, and storage calculations are based on this moisture level. Corn harvested at higher moisture must be dried down to 15.5% before storage or sale.
Corn shrink is calculated as: Shrink% = (Wet yield − Dry yield) ÷ Wet yield × 100. Or directly: Dry yield = Wet yield × (100 − actual moisture) ÷ (100 − 15.5). A 200 bu wet yield at 25% moisture shrinks to 181.1 bu at 15.5% — about 9.5% shrink.
Ideal harvest moisture is 22-25% for minimal field loss and good grain quality. Harvesting above 28% increases drying costs and kernel damage. Below 18% risks lodging, ear drop, and weather damage. Most farmers target 23-25% for optimal balance.
Yes. After physiological maturity (black layer, R6), corn loses about 0.5-1.0 moisture point per day in warm, dry conditions. In cool, humid weather, dry-down is much slower (0.25-0.5 points/day). Field drying is free but risks lodging and weather losses.
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