Grain shrinkage is the reduction in grain weight that occurs when moisture is removed during drying. The amount of shrink depends on the grain’s starting moisture, target moisture, and any additional losses that occur during handling. Water loss is usually the main source of shrink, but fines, broken kernels, and other dry-matter losses can also reduce the amount of grain available for sale.
Understanding grain shrinkage helps farmers estimate how much grain will remain after drying and what that weight loss means for storage and marketing. Agri-Systems can help farmers plan grain drying, storage, and handling systems that manage moisture and reduce avoidable grain losses.
What Is Grain Shrinkage?
Grain shrinkage is the reduction in grain weight that occurs when moisture is removed, usually during drying. Wet grain contains both water and dry matter, so removing water makes the grain weigh less. However, the percentage of moisture removed is not the same as the percentage of grain weight lost. The amount of shrink depends on the grain’s starting and final moisture levels.
Grain is commonly brought to a standard moisture level before sale so buyers can compare grain weights on a consistent basis. A buyer’s shrink deduction may include more than water loss. Depending on the buyer’s policy, it may also account for handling or dry-matter losses such as fines, broken kernels, and other losses during drying and handling.
What Causes Grain Shrinkage?
Grain shrinkage can come from moisture removal as well as small losses of grain material during drying and handling. The amount of shrink depends on how much moisture the grain contains at harvest, how far it is dried, and how much grain is lost during the process.
Moisture Loss During Drying
Moisture loss is the main cause of grain shrinkage. A grain dryer removes water from the kernels to bring them to a target moisture level for storage or sale. Grain with a higher starting moisture contains more water, so it generally loses more weight when dried to the same final moisture level.
For example, grain dried from 25% moisture to 15% will lose more weight than grain dried from 18% to 15%. The difference is based on the amount of water that must be removed, not simply the number of moisture points reduced.
Handling and Dry-Matter Loss
Some shrink can also occur when grain is moved through dryers, conveyors, augers, elevators, and other handling equipment. Fines, broken kernels, dust, foreign material, and grain left behind in equipment can contribute to additional losses. These losses are usually smaller than moisture shrink, but they can add up across a large operation.
The amount of handling or dry-matter loss varies by the grain, equipment, operating conditions, and buyer’s calculation method. A commercial shrink factor may therefore be higher than the water loss calculated from moisture alone.
Overdrying and Extra Moisture Removal
Drying grain below its intended moisture level removes more water than necessary and increases weight loss. For example, drying grain to 13% when the intended target is 15% means removing additional moisture that could otherwise remain in the grain.
The goal is to reach the appropriate moisture level for the intended storage or sale, rather than removing as much moisture as possible. This helps limit unnecessary shrink while still meeting moisture requirements.
Grain Shrinkage vs. Moisture Loss
Moisture loss and grain shrinkage are related, but they are not the same thing. Moisture loss refers specifically to the water removed from grain during drying. Grain shrinkage refers to the resulting reduction in weight. Commercial grain buyers may also account for additional losses from handling, so the shrink shown on a grain settlement may be different from the calculated water shrink.
| Term | What it means |
|---|---|
| Moisture loss | Water removed from the grain during drying |
| Water shrink | Reduction in grain weight caused by removing water |
| Handling shrink | Additional loss from fines, broken kernels, dust, spillage, and other dry-matter losses |
| Total commercial shrink | The shrink factor a buyer applies when calculating the amount of grain accepted or paid for |
The key point is that there is no single commercial shrink factor that applies to every grain buyer. A buyer may use a water-shrink calculation alone or add an allowance for handling and other losses. Always check the buyer’s current shrink and discount schedule when estimating the final weight and value of dried grain.
What Research Says About Grain Shrinkage
Research from the National Corn Handbook shows that water removal is the largest part of grain weight shrinkage during mechanical drying. In one example, 1,000 pounds of corn at 25% moisture contained 750 pounds of dry matter and 250 pounds of water. After drying to 15.5% moisture, the grain weighed about 887.6 pounds, meaning 112.4 pounds of water had been removed. That equals an 11.24% water shrink, even though the moisture content dropped by 9.5 percentage points.
How to Calculate Grain Shrinkage
To calculate grain shrinkage from moisture loss, you need the grain’s starting moisture and its target moisture. The basic formula shows what percentage of the original grain weight is lost as water:
Moisture Shrink (%) = [(Initial Moisture − Final Moisture) ÷ (100 − Final Moisture)] × 100
This calculation is based on the amount of dry matter in the grain. Dry matter does not disappear when water is removed, so it provides a way to determine the grain’s expected weight after drying.
Grain Shrinkage Calculation Example
Suppose you have 1,000 pounds of corn at 20% moisture and dry it to 15% moisture.
First, calculate the amount of dry matter:
1,000 lb × (100% − 20%) = 800 lb of dry matter
The grain will still contain those 800 pounds of dry matter after drying. At 15% moisture, dry matter makes up 85% of the grain’s total weight:
800 ÷ 0.85 = 941.2 lb
The final grain weight is therefore about 941.2 pounds. The weight lost during drying is:
1,000 lb − 941.2 lb = 58.8 lb
The moisture shrink is:
58.8 ÷ 1,000 × 100 = 5.88%
So, drying 1,000 pounds of corn from 20% to 15% moisture results in about 5.88% water shrink, before any additional handling or dry-matter losses are considered. This shows why removing 5 moisture points does not mean losing exactly 5% of the grain’s weight.
How to Calculate Final Grain Weight
You can also calculate the final grain weight directly with this formula:
Final Weight = Initial Weight × (100 − Initial Moisture) ÷ (100 − Final Moisture)
Using the same example:
1,000 × (100 − 20) ÷ (100 − 15) = 941.2 lb
To convert the final weight into market bushels for corn, divide the weight by the applicable pounds per bushel. For example, using the standard 56-pound market bushel, 941.2 pounds equals about 16.8 bushels.
How Much Does Grain Shrink Per Point of Moisture?
The amount of grain lost for each moisture point depends on the final moisture level. As grain is dried to a lower moisture level, each additional percentage point of moisture represents a slightly larger loss of grain weight.
The water shrink factor can be calculated with this formula:
Water Shrink Factor = 100 ÷ (100 − Final Moisture)
For example, at a final moisture level of 15%, the calculation is 100 ÷ 85 = 1.176%. This means each percentage point of moisture removed represents about 1.18% of the original grain weight.
| Final Moisture | Approx. Water Shrink Per Point |
|---|---|
| 15% | 1.18% |
| 14% | 1.16% |
| 13% | 1.15% |
These figures represent water shrink only. They do not include additional losses from handling, fines, broken kernels, or other dry-matter losses. A grain buyer may use a higher commercial shrink factor if its pricing or settlement policy includes these additional allowances.
How Grain Shrink Affects Grain Sales
Grain shrink affects how much grain remains for sale after drying. When moisture is removed, the grain weighs less, which reduces the final amount available for sale. The cost of drying and the buyer’s deductions can also affect the final value of the load. A shrink deduction reduces the amount of grain credited based on the buyer’s shrink factor, while a drying charge is a fee for removing excess moisture. A moisture discount is a price adjustment for grain delivered above the buyer’s preferred moisture level, while a foreign-material deduction accounts for material that does not meet the buyer’s quality requirements.
These adjustments can vary between grain buyers, so there is no single shrink or discount rate that applies to every sale. Farmers should check the buyer’s current shrink factor, drying charges, moisture discounts, and quality deductions before selling. This helps provide a more accurate estimate of how much grain will remain after drying and what it will be worth at sale.
How to Reduce Avoidable Grain Shrink
Some grain shrink is unavoidable because moisture needs to be removed to reach the right level for storage or sale. However, farmers can reduce additional losses by drying grain only to the intended moisture target and using accurate moisture measurements before and after drying. Keeping augers, conveyors, bucket elevators, and other handling equipment in good condition can also help reduce grain damage, fines, and losses during movement.
It also helps to compare the cost of on-farm drying with the buyer’s drying charges and shrink deductions before deciding where to dry grain. Tracking the grain’s weight and moisture before and after drying can show how much shrink is occurring and help identify unexpected losses. Over time, this information can help farmers make better drying and handling decisions.
Grain Shrinkage Calculation: Quick Example
A quick example can make grain shrinkage easier to understand. Suppose you have 1,000 pounds of corn at 20% moisture and dry it to 15% moisture. The grain contains 800 pounds of dry matter, which remains after the water is removed. At 15% moisture, that 800 pounds of dry matter represents about 941.2 pounds of finished grain.
| Calculation | Result |
|---|---|
| Starting weight | 1,000 lb |
| Starting moisture | 20% |
| Final moisture | 15% |
| Final weight | 941.2 lb |
| Weight lost | 58.8 lb |
| Moisture shrink | 5.88% |
So, drying the 1,000 pounds of corn from 20% to 15% moisture results in about 58.8 pounds of water loss, or 5.88% moisture shrink. This calculation represents water shrink only and does not include any additional handling or dry-matter losses that a buyer may include in its commercial shrink factor.
Need a Better Grain Drying and Handling Setup?
Managing grain moisture starts with the right drying and handling equipment. Agri-Systems can help you select and plan grain dryers, conveyors, elevators, storage systems, and other equipment based on your operation and capacity needs.
If you’re planning a new grain system or upgrading an existing one, talk with the Agri-Systems team about your project. Contact Agri-Systems to discuss your grain drying, handling, and storage needs.
Conclusion
Grain shrinkage is a normal part of drying grain because removing moisture reduces its weight. The key is to understand how much weight will be lost before drying and how the buyer calculates shrink, drying charges, and other deductions. Using the starting and final moisture levels makes it possible to estimate final grain weight and water shrink accurately.
For farmers, tracking moisture, weight, and handling losses can help reduce avoidable shrink and make drying decisions easier. Agri-Systems can help with grain drying, handling, and storage systems designed to move and condition grain efficiently while maintaining grain quality.
Frequently Asked Questions
What is grain shrinkage?
Grain shrinkage is the reduction in grain weight that occurs when moisture is removed during drying. Additional losses from handling, fines, broken kernels, and other dry-matter losses may also be included in a buyer’s commercial shrink calculation.
How do you calculate grain shrinkage?
You can calculate moisture shrink by comparing the starting and final moisture levels. The formula is Moisture Shrink (%) = [(Initial Moisture − Final Moisture) ÷ (100 − Final Moisture)] × 100. This calculates the percentage of the original grain weight lost as water.
How much does corn shrink when dried?
Corn shrink depends on its starting and final moisture levels. For example, drying 1,000 pounds of corn from 20% to 15% moisture results in about 58.8 pounds of water loss, or approximately 5.88% moisture shrink. The actual commercial shrink may be higher if the buyer includes handling or other allowances.
Does grain shrinkage include handling loss?
Not always. Moisture shrink refers specifically to the weight lost when water is removed. Handling losses, such as fines, broken kernels, dust, or spillage, are separate losses, although a buyer may include an allowance for them in its commercial shrink factor.
Is grain shrink the same as a drying charge?
No. Grain shrink is a reduction in the amount of grain credited or sold after moisture and other applicable losses are accounted for. A drying charge is a fee for removing excess moisture. A buyer may apply both a shrink deduction and a drying charge, depending on its pricing and discount schedule.
