Accurately calculate grain test weight (lbs/bu) from sample measurements and estimate financial dockage for corn, wheat, soybeans, and other crops.
Grain Test Weight Analysis
Enter your sample details below to calculate test weight and potential revenue loss.
Corn (Std: 56 lbs/bu)
Soybeans (Std: 60 lbs/bu)
Wheat (Std: 60 lbs/bu)
Oats (Std: 32 lbs/bu)
Barley (Std: 48 lbs/bu)
Custom Crop
Select the crop to set standard test weight baselines.
Grams
Lbs
Ounces
Weight of the grain in your test container.
Please enter a positive weight.
1 Quart (Standard Kettle)
1 Pint
1 Liter
Volume of the container used to measure the sample.
Total bushels you plan to sell.
Current base price per bushel.
Price reduction for every 1 lb/bu below standard.
Calculated Test Weight
0.0 lbs/bu
waiting for input…
Standard Target:56 lbs/bu
Deficit/Surplus:0.0 lbs
Est. Price Dockage:$0.00
Net Revenue:$0.00
Formula Used: Test Weight = (Sample Weight converted to lbs) × (Bushels per Container Factor). Financial adjustments are applied based on the difference from standard weight.
What is a Test Weight Calculator?
A test weight calculator is a critical agricultural tool used by farmers, grain elevators, and commodity traders to determine the density of grain, typically measured in pounds per bushel (lbs/bu). Test weight serves as a primary indicator of grain quality and directly impacts the sale price of crops like corn, soybeans, wheat, and oats.
Farmers use this tool during harvest to estimate the grade of their yield. If grain density falls below the United States Department of Agriculture (USDA) standards—for example, 56 lbs/bu for #1 yellow corn—buyers will apply a financial penalty known as "dockage." This calculator helps producers forecast these penalties and make informed decisions about storage, drying, or blending grain to maximize profitability.
Test Weight Calculator Formula and Explanation
The mathematical basis for calculating test weight involves scaling the weight of a known small volume sample up to the volume of a Winchester bushel (2,150.42 cubic inches).
The Core Formula:
Test Weight (lbs/bu) = (Weight of Sample in lbs) × Conversion Factor
The conversion factor depends on the container size used for the sample. For the industry-standard 1-quart kettle:
1 Winchester Bushel ≈ 32 Dry Quarts
Therefore, Test Weight = Weight of 1 Quart (lbs) × 32
Table 1: Key Variables in Test Weight Calculation
Variable
Meaning
Unit
Typical Range
Sample Weight
Mass of grain in the test cup
Grams (g) or Pounds (lbs)
300g – 1100g (per quart)
Standard TW
Target density for Grade #1
lbs/bu
32 (Oats) to 60 (Wheat)
Dockage Rate
Penalty per point under standard
$/point
$0.02 – $0.05
Pack Factor
Settling of grain in bin
Percentage
1.02 – 1.05
Practical Examples (Real-World Use Cases)
Example 1: The Wet Corn Harvest
A farmer harvests corn with high moisture. They take a 1-quart sample which weighs 800 grams.
Step 2: Scale to bushel (Quart is 1/32 of a bushel). 1.7637 lbs × 32 = 56.4 lbs/bu.
Result: The corn meets the 56 lbs/bu standard. No dockage applies.
Example 2: Light Wheat Penalty
A producer has 10,000 bushels of wheat. The standard is 60 lbs/bu. Their sample tests at 57 lbs/bu (3 points under). The elevator charges $0.04 per point discount.
Deficit: 60 – 57 = 3 points.
Discount Per Bushel: 3 points × $0.04 = $0.12/bu.
Total Loss: 10,000 bushels × $0.12 = $1,200 lost revenue.
How to Use This Test Weight Calculator
Select Commodity: Choose your crop (Corn, Wheat, etc.) to automatically load the USDA standard weight.
Weigh Your Sample: Fill a container (standard quart kettle recommended) until it overflows, level it off with a striker, and weigh the contents.
Enter Data: Input the weight in grams, ounces, or pounds, and select your container size.
Financials (Optional): Enter your total bushels, current market price, and the buyer's discount rate to see the net financial impact.
Analyze: Check the "Net Revenue" and the chart to see how much value you might be losing due to low density.
Key Factors That Affect Test Weight Results
Several biological and environmental factors influence the final test weight of your grain:
Moisture Content: Generally, as grain dries, test weight increases because kernels shrink and pack more tightly. However, artificial drying at high heat can damage kernels and lower test weight.
Kernel Damage: Cracked or broken kernels occupy more space relative to their weight compared to whole kernels, reducing overall density.
Foreign Material (FM): Trash, husks, or weed seeds usually have a lower density than the grain itself, dragging down the test weight average.
Variety/Genetics: Specific hybrids are bred for higher density. Choosing the right seed is the first step in managing test weight.
Growing Conditions: Stress during the "fill" period (drought, frost, or disease) prevents kernels from reaching full starch accumulation, resulting in "light" grain.
Handling: Excessive auguring or dropping of grain can increase breakage, inadvertently lowering test weight before the point of sale.
Frequently Asked Questions (FAQ)
What is the standard test weight for corn?
The USDA standard for U.S. No. 1 Yellow Corn is 56 lbs/bu. If your corn tests below this, you may be subject to price discounts at the elevator.
Does test weight change during storage?
Yes. As grain dries (loses moisture) in storage, the volume shrinks slightly more than the weight loss, often resulting in a slight increase in test weight ("phantom gain"). However, spoilage will reduce it.
Why does test weight matter for farmers?
It is a measure of quality. Higher test weight implies more starch/meat per bushel, which is valuable to end-users (ethanol plants, feed mills). Low test weight reduces the quantity of usable product, leading to financial penalties.
How do I convert grams per quart to lbs per bushel?
The simplified factor is: (Grams per Quart / 453.6) × 32. Alternatively, multiply Grams per Quart by approximately 0.0705 to get lbs/bu.
Can I blend grain to improve test weight?
Yes, blending high-test-weight grain with lower-quality grain is a common strategy to meet the elevator's minimum standard and avoid dockage.
Is test weight the same as bushel weight?
Yes, these terms are often used interchangeably in the industry to describe the volumetric density of the grain.
Does test weight affect yield calculations?
Indirectly. Yield monitors measure mass flow, but sold bushels are volume-adjusted. If your corn is 54 lbs/bu, you need more cubic volume to equal one standard 56-lb bushel.
What tools do I need to measure this manually?
You need a calibrated scale, a standard volume measure (usually a Winchester quart or pint), and a striker stick to level the grain flat across the top of the container.
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