Grain Shrink Calculator
Shrink wet bushels to dry bushels across moisture levels.
What it does
Drying removes water but keeps dry matter. Shrink compares wet bushels to dry bushels at the target moisture. A thousand wet bushels at 25 percent drying to 15 percent does not stay a thousand.
The tool above takes wet bushels plus initial and final moisture and returns dry bushels, shrink percent, and water share. The defaults 1000, 25, and 15 match the worked example, so the page opens showing 882.35 bu.
Dry matter is wet times (100 minus initial) over 100. Dividing by (100 minus final) over 100 rescales to the target moisture. Here 1000 times 75 over 85 is 882.35. Shrink is one minus dry over wet.
Use this for settlement, storage planning, and drying charges. Test weights, fines, and handling loss sit outside. Verify moisture with calibrated meters and probe multiple spots.
This page shows the formula, one full hand checked example at 1000 bu, a reference table, and practice checks that run through the tool.
How to use
- Type wet bushels at start moisture.
- Type initial moisture percent.
- Type final moisture percent below initial.
- Read Dry bushels as the main result.
- Read Shrink percent for settlement.
- Probe loads in several spots for true moisture.
Formula
- wet
- Bushels at initial moisture.
- in/out
- Moisture percents, out below in.
- dry
- Bushels at final moisture.
Moisture here is wet basis percent. Dockage and test weight shifts sit outside this water only math.
Worked example
Example: 1000 bu, 25 to 15 percent
Dry a thousand bushels from 25 to 15 percent moisture.
- Dry matter factor: (100 minus 25) = 75.
- Target divisor: (100 minus 15) = 85.
- Dry: 1000 x 75 / 85 = 882.3529 bu.
- Round: 882.35 bu.
- Shrink: 100 x (1 minus 0.88235) = 11.76 %.
- Water share: 1000 minus 882.35 = 117.65 bu.
Reference table
| To % | Dry of 1000 bu | Shrink |
|---|---|---|
| 20 | 937.50 bu | 6.25 % |
| 15 | 882.35 bu | 11.76 % |
| 13 | 862.07 bu | 13.79 % |
Limits
- Water only. Fines and handling loss excluded.
- Wet basis moisture assumed.
- Meter error carries straight into dry.
- No drying energy or cost here.
Common mistakes
- Subtracting moistures directly (25 minus 15 = 10 percent) instead of ratio math.
- Mixing dry basis with wet basis percents.
- Using one probe for a whole bin.
- Forgetting final must sit below initial.
- Billing wet bushels as dry.
Try it yourself
Quick checks. Answers sit tucked under each question.
500 bu, 20 to 15?
Dry 470.59 bu, shrink 5.88 %, water 29.41 bu.
1000 bu, 25 to 20?
Dry 937.50 bu, shrink 6.25 %.
Questions
1000 at 25 to 15?
882.35 bu dry.
Shrink?
11.76 % here.
Why not 10 percent?
Water base shifts. Ratio math, not subtraction.
Dry basis?
Not here. This tool is wet basis.
Probe?
Several spots. Single probes mislead.
Cost?
Multiply shrink bushels by price plus drying fees.