Test weight for Canadian grains
Test weight, or bushel weight, is a measure of a grain’s density, which is expressed as the weight of the grain packed in a specified volume. A grain’s test weight is commonly expressed in kilograms per hectolitre (kg/hL) or pounds per bushel (lb/bu).
Test weight is a grade-determining factor for many grains under the Canada Grain Act. The Official Grain Grading Guide specifies minimum test weights required to make grades for certain grains.
Determining test weight
In Canada, test weight is assessed after dockage is removed, as defined in the cleaning procedures for each grain. Test weight for corn is determined before removing cracked corn and foreign material.
In the Official Grain Grading Guide, test weight is expressed in kilograms per hectolitre (kg/hL), or the weight of 100 litres of grain. In practice, the determination of test weight uses a half-litre cylinder and grain samples weighed to the nearest gram. The gram-per-half-litre weight is converted to the kg/hL equivalent using the grain’s test weight conversion chart.
Samples are graded Sample Account Light Weight only if the test weight is lower than the minimum test weight established for the lowest grade of that grain, and in accordance with the Order of Precedence in the Official Grain Grading Guide.
Test weight calculators and conversion charts for Canadian grains
We develop calculators and conversion charts by collecting data from a wide range of grain samples and determining the mathematical relationships between the weight of uncompacted grain in a half-litre cylinder and the weight of compacted grain using a Schopper chondrometer. A specific equation is used for each grain to predict its approximate test weight in kg/hL using the half litre weight of a grain sample. Test weight calculators and conversion charts are also used to convert kg/hL to bushel weights. Additional calculators are available to convert units of measurement (for example, pounds to kilograms) and to help determine the volume of a lot of grain.
Using the test weight conversion charts
Charts are provided for converting uncompacted grain sample weights (g/0.5 L) to:
- official compacted hectolitre weights (kg/hL)
- bushel weights for compacted bushels-Avery (lb/bu-A)
- bushel weights for uncompacted bushels-Winchester (lb/bu-W)
For example, here’s a portion of the conversion chart for wheat:
| g/0.5 L | kg/hL | lb/bu-A | lb/bu-W |
|---|---|---|---|
| 297 | 61.2 | 49.1 | 46.1 |
| 298 | 61.4 | 49.3 | 46.2 |
| 299 | 61.6 | 49.4 | 46.4 |
| 300 | 61.8 | 49.6 | 46.6 |
| 301 | 62.0 | 49.7 | 46.7 |
| 302 | 62.2 | 49.9 | 46.9 |
Note that the conversion is strictly for uncompacted half-litre weights that are specific for the grain type.
Selecting the appropriate bushel weight
Grain test weight is commonly referred to as bushel weight and expressed as pounds per bushel (lb/bu). However, a bushel in Canada may not be equal to a bushel in the United States (U.S.). In Canada, the bushel is based on the British Imperial (Avery) bushel (36.37 L), which is slightly larger than the U.S. (Winchester) bushel (35.24 L).
Make sure you know which type of bushel is being used when making formal grain transactions. If you are selling your grain by contract to a company in the U.S., test weights specified in the contract are in pounds per bushel, which will usually mean the U.S. (Winchester) bushel (lb/bu-W). However, if you get a test weight measurement for your grain at a primary elevator in Canada, it will be in British Imperial (Avery) bushels (lb/bu-A) and will also include compaction. The difference between the 2 bushel weights could affect the end result of calculated tonnage.
Bushel weight in Canada
In Canada, the grain bushel weight is based on the British Imperial bushel and accounts for grain compaction. Canadian bushel weights are expressed as weight in pounds per bushel-Avery (lb/bu-A).
Bushel weight in the United States
In the U.S., the grain bushel weight is based on the U.S. bushel and does not account for compaction. U.S. bushel weights are expressed as weight in pounds per bushel-Winchester (lb/bu-W). The U.S. method of determining bushel weights uses dry quart measures similar to the half-litre cylinders, but the grain is not purposely compactedweight is not adjusted to reflect grain compaction.
Converting bushels to tonnes
If all crops had the same test weight or grain density, then one bushel taken from any crop will weigh the same. However, this is not the case and one bushel of a high-density crop will weigh more than one bushel of a low-density crop.
There is no single conversion factor, even for a specific grain. If you are converting from bushels to tonnes, you should use the specific test weight of the grain rather than assuming that one tonne is equivalent to a single standard number of bushels of that grain.
Example
1 tonne wheat: bushel weight 65 lb/bu-A
- Convert pounds to kilograms: (65 lb x 0.4536 kg/lb) = 29.48 kg/bu-A
- 1 tonne = 1000 kg contains 1000/29.48 = 33.9 bu-A
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