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How Mushrooms Are Graded

How Mushrooms Are Graded

Grading mushrooms is a way of applying a standardized measurement when looking at mushrooms. There are different standards by which mushrooms can be judged as a lot.

As an example, the USDA has its specific standards by which mushrooms are graded.

On the other hand, mushrooms are inspected only by the United States Food and Drug Administration (FDA).

A general aspect of grading mushrooms defined by the USDA is that they are of similar size, age and are free from diseases, injuries, and damages.

And they need to be fresh and should be free of decay.

They need to be trimmed neatly, have a nice shape, and have to be free from open veils.

These are the general requirements for grading mushrooms.

The USDA defines two numbers or grades. U.S. No 1 and U.S No 2.

How Mushrooms are graded

Mushrooms are graded by their size and by meeting certain tolerance levels. These tolerance levels are defined as percentage levels. As an example, the percentage of mushrooms meeting the requirements in terms of size, age, being free from diseases, injuries, and damages need to be 97.5% for U.S No 1 and 90% for U.S No 2 grade.

Grading Mushrooms

In this section, I will go into the different variables that are taken into account when grading mushrooms defined by the US Department of Agriculture as well as the needed values for the U.S No. 1 grade.

U.S No. 2 grade uses the same requirements but has a bigger tolerance for open veils and defects.


When looking at the size of mushrooms, their diameter is relevant. The size classification is as follows:

Small to medium: 1-5/8 inches (diameter)

Large: >1-5/8 inches (diameter)


Tolerances in mushrooms are used to define the percentage value of mushrooms in a lot that are allowed to not meet certain grading requirements. It is defined by weight.

At Shipping Point

At shipping point. 10% of mushrooms are allowed to have open veils. In addition, 10% are allowed to fail the requirements in terms of this grade, however, no more than 1% can be affected by diseases, spots, and decay.

En route or already at the destination

Here, 25% are allowed to have open veils. But no more than 10% can fail.

For off size

10% of mushrooms are allowed to fail the very specific size requirements.

As mentioned above these are the requirements for U.S No. 1. U.S No. 2 has higher tolerance levels and is using the same categories.

Why grading Mushrooms is important

There are grading standards for all fresh and processed fruits, vegetables and speciality crops.

Grading allows judging the overall quality of eg. a lot and defines concrete measurement factors.

Grading is specifically important in food processing and needs trained operators. Apart from crops, vegetables and fruits also meat and cheese are graded among many other foods and beverages.

The purpose here is to allow for a clear and accurate measurement that is consistent. Furthermore, grading allows for better compliance in terms of food safety and regulations.

In general graded food means that it can be eaten by humans and is thus ready for consumption.

In some cases, it also simply means that humans can come in contact with certain food safely.