Wet grain weighs more than dry grain. That difference matters at the elevator, because buyers adjust what they pay based on how much weight will disappear when they dry your load to a standard moisture. That adjustment is called moisture shrinkage or pencil shrink, and getting it wrong costs money on both sides of the transaction.
The Grain Moisture Shrinkage Calculator shows you the exact percentage of weight your grain will lose when dried from its current moisture to any target moisture level. Enter your initial moisture content, your target moisture, and your grain weight, and the calculator returns the moisture shrink percentage, the weight after drying, and the pounds of water removed.
What Is Grain Moisture Shrinkage Calculator
Grain is made up of two components: water and dry matter. Dry matter is the actual grain. When you dry grain, the water leaves but the dry matter stays. Because moisture is expressed as a percentage of total weight, removing water changes both the numerator and the denominator at the same time. That is why a nine-point moisture reduction does not produce a nine-percent weight loss.
When grain dries from 25% moisture to 15.5%, the moisture shrinkage is 11.24%, not 9.5%. The difference matters when you are selling thousands of bushels. Grain buyers account for this by pencil shrinking wet grain: they calculate how many dry bushels the wet load contains before pricing it.
Standard Moisture Content by Grain Type
The grain trade uses established base moisture levels to set a consistent pricing standard.
These are the standard moisture contents and test weights used in commercial grain transactions in the United States:
| Grain | Standard Moisture Content | Standard Test Weight |
|---|---|---|
| Corn (shelled) | 15.5% | 56 lb per bushel |
| Soybeans | 13.0% | 60 lb per bushel |
| Wheat | 13.5% | 60 lb per bushel |
| Grain sorghum | 14.0% | 56 lb per bushel |
| Barley | 14.5% | 48 lb per bushel |
Any grain delivered above these moisture levels will be adjusted for the excess water. Grain delivered below these levels is generally still priced at the standard, so drying too far past the target costs you weight without a compensating price improvement.
The Grain Moisture Shrinkage Calculator Formula
The core formula for moisture shrinkage calculates the percentage of the original weight that will be lost when grain is dried from an initial moisture content to a final moisture content.
Moisture Shrink (%) = [1 − (100 − Initial MC) ÷ (100 − Final MC)] × 100
Where:
- Initial MC = moisture content of the grain before drying (%)
- Final MC = target moisture content after drying (%)
This formula works from the principle that dry matter is constant. It calculates the final weight that contains the same dry matter at the lower moisture level, then expresses the weight reduction as a percentage of the original weight.
The same relationship expressed as a weight multiplier:
Weight After Drying = Original Weight × (100 − Initial MC) ÷ (100 − Final MC)
This version directly gives you the weight of grain remaining after drying.
What Each Variable Represents
Initial Moisture Content (Initial MC) The moisture content of your grain at the time of measurement, expressed as a percentage of total weight. This is the wet-weight basis used throughout the grain industry. Corn at harvest commonly runs from 18% to 30%, depending on variety and harvest timing.
Final Moisture Content (Final MC) The target moisture level after drying. This is usually the elevator’s standard moisture for the grain you are selling, or the recommended storage moisture for your intended storage duration. Purdue University Extension recommends 15.5% for corn stored up to six months, 14% for up to twelve months, and 13% for storage beyond one year.
Original Weight The total weight of wet grain before drying, in pounds, kilograms, or tonnes depending on your preferred unit. The shrink percentage applies proportionally regardless of unit.
Worked Example 1: Corn
Scenario: You harvest 50,000 lb of corn at 25% moisture. The elevator prices corn at 15.5% moisture. How much will the load weigh after shrinkage?
Step 1: Calculate dry matter in the original load
Dry matter = 50,000 × (1 − 0.25) = 50,000 × 0.75 = 37,500 lb
Step 2: Calculate the weight at 15.5% moisture
At 15.5%, dry matter is 84.5% of total weight.
Weight after drying = 37,500 ÷ 0.845 = 44,379 lb
Step 3: Calculate moisture shrink percentage
Moisture Shrink = [1 − (100 − 25) ÷ (100 − 15.5)] × 100 = [1 − 75 ÷ 84.5] × 100 = [1 − 0.88757] × 100 = 11.24%
Step 4: Confirm weight loss
Weight removed = 50,000 − 44,379 = 5,621 lb of water removed
Interpretation: Your 50,000 lb load loses 5,621 lb before it is priced. At 56 lb per bushel, you started with 892.9 wet bushels and end with 792.5 dry bushels. That 100.4-bushel difference represents moisture shrinkage alone, before any handling loss.
Worked Example 2: Wheat
Scenario: You deliver 20,000 lb of wheat at 18% moisture. The elevator prices wheat at 13.5% moisture. What is the moisture shrink?
Step 1: Apply the formula
Moisture Shrink = [1 − (100 − 18) ÷ (100 − 13.5)] × 100 = [1 − 82 ÷ 86.5] × 100 = [1 − 0.94798] × 100 = 5.20%
Step 2: Calculate adjusted weight
Weight after shrinkage = 20,000 × (100 − 18) ÷ (100 − 13.5) = 20,000 × 82 ÷ 86.5 = 18,960 lb
Interpretation: Your 20,000 lb wheat load shrinks to 18,960 lb at trade moisture. The elevator will price 18,960 lb rather than your delivered weight of 20,000 lb.
The Water Shrink Factor
Grain buyers and drying tables use a simplified version of the shrinkage calculation called the water shrink factor. This is a per-point multiplier that tells you how many percent of original weight is lost for each percentage point of moisture removed.
Water Shrink Factor = 100 ÷ (100 − Final Moisture Content)
The factor is constant for a given final moisture level. It changes when the target moisture changes.
| Final Moisture (%) | Water Shrink Factor (% loss per point) |
|---|---|
| 15.5 | 1.183 |
| 15.0 | 1.176 |
| 14.0 | 1.163 |
| 13.5 | 1.156 |
| 13.0 | 1.149 |
| 12.0 | 1.136 |
To use the factor, multiply points of moisture removed by the factor for your target moisture:
Total Water Shrink (%) = Points of Moisture Removed × Water Shrink Factor
Example: Drying corn from 25% to 15.5% removes 9.5 percentage points. Total Water Shrink = 9.5 × 1.183 = 11.24%
This matches the direct formula result above, confirming both methods produce the same answer.
Moisture Shrink vs. Total Shrink
The moisture shrink formula shown above accounts only for water loss. Buyers often apply a slightly higher shrink figure called total shrink, which includes a small handling loss allowance on top of the water shrink.
Total Shrink (%) = Water Shrink + Handling Loss
Handling loss covers dry matter removed through the drying process itself. It includes volatile compounds such as oils, broken kernels, and fine material. Research at Iowa State University found on-farm handling losses ranged from 0.22% to 1.71%, with a three-year average of 0.82%. Commercial drying facilities showed a range of 0.64% to 1.33%.
Grain buyers express total shrink as a constant shrink factor applied per point of moisture removed. Common constant shrink factors range from 1.2% to 1.5% per point, compared to the pure water shrink factor of about 1.18% per point at 15.5% moisture. The difference between the constant factor and the water shrink factor represents the handling loss assumption embedded in the buyer’s pricing.
What this means when selling: If a buyer quotes a 1.3% constant shrink factor on 28% corn going to 15.5%, the handling loss assumption is 1.46%. The Iowa State research average was about 0.82%. Ask buyers what shrink factor they use so you can compare the embedded handling loss against this reference range. Factors above 1.5% per point deserve scrutiny.
How to Measure Initial Moisture Content
The moisture shrink result is only as accurate as your moisture reading. Two measurement approaches are common.
Portable moisture meters use electrical resistance or capacitance to estimate moisture content. They are fast and practical at harvest. Accuracy depends on calibration, grain temperature, and grain cleanliness. Read the manufacturer’s guidance for your specific meter and grain type.
Commercial elevator moisture testing uses approved equipment and USDA-standardized procedures. The elevator’s reading is the one that determines your shrink calculation for pricing. If your portable meter reads differently from the elevator’s meter, the elevator’s certified reading governs the transaction.
For storage planning rather than sale pricing, take several measurements from different locations in a load and average them, since moisture can vary across a delivery.
How to Interpret the Calculator Output
Moisture Shrink (%): The percentage of original weight that will be lost when dried to the target moisture. This is the pure water-loss shrinkage figure.
Adjusted Weight: The weight of grain remaining after drying, in the same unit you entered.
Water Removed: The pounds or kilograms of water that will leave the grain during drying. This determines how hard your dryer works and how much fuel or LP is consumed.
Dry Bushels: If you enter your grain type, the calculator converts adjusted weight to dry bushels using the standard test weight. This tells you how many priced bushels your load represents at trade moisture.
Use these outputs to:
- Compare what a buyer’s pencil shrink calculation will produce versus the actual water shrink
- Evaluate whether to sell wet, dry on-farm, or use custom drying
- Estimate storage weight after expected field dry-down
- Plan drying fuel usage based on water to be removed
Accuracy and Limitations
The moisture shrink formula assumes that all weight loss during drying is water. In practice, a small portion of dry matter also leaves with the grain exhaust. The calculator returns moisture shrink only; it does not calculate handling loss, drying fuel cost, or dryer efficiency.
The result depends entirely on the accuracy of your moisture readings. A one-point error in initial moisture content changes the shrink result meaningfully on large loads. On 100,000 lb of corn at 25% moisture going to 15.5%, a one-point moisture error changes the shrink by about 1,183 lb, which equals roughly 21 bushels.
The calculator uses the wet-weight moisture basis, which is standard in the U.S. grain industry. Some international markets use the dry-weight basis. The two are not interchangeable; confirm which basis your contract uses before entering values.
Common Calculation Mistakes
Using percentage points as the shrink percentage. A nine-point moisture reduction is not a nine-percent weight loss. The actual shrink is always larger than the moisture point difference because the formula accounts for the changing relationship between water and dry matter.
Confusing moisture shrink with total shrink. Buyers add a handling loss to moisture shrink when they pencil shrink. The number on your settlement sheet reflects total shrink, which is higher than the water-shrink-only figure this calculator produces.
Not accounting for grain drier than standard. If soybeans come in at 11% moisture and the trade moisture is 13%, you hold more dry matter per bushel than the standard. Most buyers will not pay extra for that extra dry matter. Delivering grain at or close to the target moisture prevents this loss of value.
Rounding intermediate results. For large loads, round only the final answer. Rounding intermediate values across a multi-step calculation introduces compounding errors that become meaningful at commercial scale.
Frequently Asked Questions
What is moisture shrinkage in grain?
Moisture shrinkage is the percentage of weight that grain loses when dried from a higher to a lower moisture content. Because dry matter stays constant while water leaves, the weight loss is always greater than the simple difference between the two moisture levels. A 10-point moisture reduction produces roughly 11 to 12 percent weight loss, depending on the starting and ending moisture values.
What is the formula for grain moisture shrinkage?
The moisture shrink formula is: Moisture Shrink (%) = [1 − (100 − Initial MC) ÷ (100 − Final MC)] × 100. This calculates the share of original weight that will be removed as water during drying. An equivalent form for weight after drying is: Final Weight = Original Weight × (100 − Initial MC) ÷ (100 − Final MC).
What is the standard moisture content for corn, wheat, and soybeans?
The U.S. standard moisture contents are 15.5% for corn at 56 lb per bushel, 13.5% for wheat at 60 lb per bushel, and 13.0% for soybeans at 60 lb per bushel. These are established by USDA grain standards and are used by elevators to set a consistent pricing basis. Grain above these levels is discounted for the excess moisture.
What is a water shrink factor and how is it calculated?
The water shrink factor is the percentage of original weight lost per percentage point of moisture removed, at a given final moisture level. It is calculated as: Water Shrink Factor = 100 ÷ (100 − Final Moisture Content). For corn dried to 15.5%, the factor is 1.183% per point. For 13.5% wheat, it is 1.156% per point. Multiply this factor by the points of moisture removed to get total water shrink.
What is the difference between moisture shrink and total shrink?
Moisture shrink covers only the weight of water removed. Total shrink also includes a handling loss allowance for dry matter that leaves the grain during the drying process (through broken kernels, fine material, and volatile compounds). Buyers express total shrink as a constant shrink factor, typically 1.2% to 1.5% per point, compared to the pure water shrink factor of about 1.18% per point at 15.5% corn moisture. The difference between the buyer’s factor and 1.18 is the embedded handling loss assumption.
How much weight does corn lose when dried from 25% to 15.5%?
Corn at 25% moisture loses 11.24% of its original weight when dried to 15.5%. For every 1,000 lb of wet corn, 112.4 lb of water is removed, leaving 887.6 lb of corn at 15.5% moisture. The dry matter (750 lb) remains unchanged throughout the drying process.
Does this calculator apply to grain stored on-farm?
Yes. The formula applies to any situation where grain moisture changes: drying, field dry-down, or storage dry-down. Enter the initial moisture at the time of measurement and the target moisture you plan to reach or store at. The output shows the weight you will have after reaching that moisture level. This is useful for estimating bin inventory after storage conditioning.
What is pencil shrink?
Pencil shrink is the grain buyer’s calculation that adjusts the gross weight of a wet load to the equivalent weight at the buyer’s target moisture. Buyers apply a shrink factor (either a water shrink table or a constant factor per point) to determine how many dry bushels they are actually purchasing. Growers should understand pencil shrink because the shrink method and the final moisture target both affect the net bushels and the price received.
Why is my weight loss larger than the point difference in moisture?
Because moisture is expressed as a fraction of total weight, removing water changes the total weight, which changes the denominator in the moisture calculation. As water leaves, the same amount of dry matter now makes up a larger fraction of the lighter load. That is why a 10-point moisture reduction always produces a weight loss greater than 10 percent of the original weight.
Sources and Methodology
- Hicks, D.R., and H.A. Cloud
- University of Wisconsin.
- Purdue University Extension
- USDA Grain Standards
Formula verification: All worked examples were independently recalculated. Moisture shrink formula and water shrink factor table values were cross-checked against NCH-61 and FSA-1078 source documents.