09/11/2026
What is Test Weight?
Test weight is a measurement of bulk density, or weight per volume. For corn specifically, test weight is determined by measuring the weight of shelled grain (at 15.5% moisture) required to fill the volume area equivalent to that historical, volume-based bushel (32 quarts). The USDA designates 5 grades by which yellow corn is categorized based on test weight. Grading of corn also
includes variables such as damaged kernels and foreign material, but for our purposes here we will focus on only test weight.
Test Weight & Grain Value
When corn test weight is below 54 pounds, the grain merchandiser may pay less for those bushels. This value reduction is referred to as “dockage,” and is applied to recover increased storage and
transportation cost for that grain, and to cover potential discounting (based on U.S. Grade) by the eventual purchasing party. The specific value of dockage will vary by merchandiser.
Test Weight & Grain Moisture
The test weight value used to determine U.S. Grade is a measure of corn bulk density (weight by volume) at 15.5% moisture. Corn is often sold at a grain moisture content above, or sometimes
below, 15.5% moisture. The test weight of grain at 15.5% moisture will be higher (heavier) than it is at higher grain moisture contents.
Test Weight & Yield
There is often confusion between test weight and yield, and the relationship between the two. Hybrid yield is defined as the number of bushels (56 pound increments) harvested per acre. There
is no correlation between hybrid yield and test weight. A hybrid with the capability to produce high yields may produce grain with a test weight that is exceptionally high, average, or very low.
Variables Impacting Test Weight
The physical kernel characteristics inherent to a hybrid greatly impact test weight. For example, a small, dense kernel that packs together tightly will contribute to a higher test weight than a large
starchy kernel that does not pack well. Also, kernels with a smooth cap will pack better (higher test weight) compared to kernels with a rough cap (average or lower test weight). stress during grain fill
can negatively impact the potential test weight of a hybrid in any individual field. This reduction may result from many different types of stress, including leaf diseases, root or stalk rots, poor soil
fertility, and/or drought, hail or early frost. These stresses reduce the amount of sugar produced by the plant and therefore how much is available to deposit as starch in the kernels during grain fill.
The net result of this sugar production deficiency, or “short-fall” will be both smaller kernels and reduced test weight, with more severe stress resulting in a greater reduction.