How it works
Drying removes water and nothing else, so the dry matter stays constant. The weight after drying is the dry matter divided by (1 − final moisture); before drying it was the dry matter divided by (1 − initial moisture). The ratio gives the water shrink.
Shrink per point of moisture is not exactly constant: it is 100 ÷ (100 − final moisture), about 1.18% per point when drying to 15.5%. Grain buyers may charge more than water shrink for handling and drying.
Worked example
10,000 bushels of corn dried from 25% to 15.5% moisture:
- Water shrink = (25 − 15.5) ÷ (100 − 15.5) × 100 = 11.24%
- Per point = 100 ÷ (100 − 15.5) = 1.183% per point
- Start = 10,000 bu × 56 lb = 560,000 lb; end = 497,041 lb (8,876 bu)
| Input | Value |
|---|---|
| Crop | Corn (shelled), 56 lb/bu |
| Wet grain (bushels at standard weight) | 10000 bu |
| Initial moisture | 25 % |
| Final moisture | 15.5 % |
| Result | Value |
|---|---|
| Water shrink | 11.24 % |
| Shrink per point of moisture | 1.183 % per point |
| Weight after drying | 497,041 lb |
| Bushels after drying | 8,876 bu |
| Water removed | 62,959 lb |
Assumptions and limits
- Moistures are wet basis, as grain meters read. Wood moisture content is usually quoted dry basis; do not mix them.
- Only the water leaving the grain is counted: no handling loss, foreign material, kernel breakage, or drying fuel.
- Bushels after drying use the standard bushel weight for the crop, an approximation when test weight changes.
Common questions
How much shrink is corn dried from 25% to 15%?
About 11.8% at a 15% final moisture: (25 − 15) ÷ 85. Drying to 15.5% gives 11.2%.
Why is shrink about 1.18% per point?
Each point removes 1% of the wet weight as water, but the remaining grain weighs less, so per point it is 100 ÷ (100 − final moisture).
Is elevator shrink higher than water shrink?
Often, since elevators add a handling allowance. Ask what your buyer charges.
Does the formula work for other grains?
Yes; it is just conservation of dry matter. Choose the crop for standard bushel weights.
Sources
- Moisture shrink = (M_i − M_f) ÷ (100 − M_f), from conservation of dry matter (South Dakota State and University of Wisconsin Extension shrink guides).
- Standard bushel weights: corn 56, soybeans and wheat 60, barley 48, oats 32 lb (USDA grain standards, OSU Extension).
- Read them: SDSU Extension: Corn grain moisture discount
Updated 2026-09-30