Egg grading sorts eggs two ways: by quality, AA, A or B, and by size, from Peewee to Jumbo. Quality is judged by candling, holding the egg to a bright light: an AA egg has a clean, normal shell, an air cell no deeper than 1/8 inch, a firm white and a yolk you can barely see; an A egg allows an air cell to 3/16 inch, a reasonably firm white and a yolk outline that's fairly well defined; anything past that, or with an abnormal shell, is B. Size is by weight, per dozen: Large is at least 24 ounces a dozen, Extra Large 27, Jumbo 30. These are USDA's standards; the USDA grade shield on a carton means USDA's grading service graded them, while your state's egg law decides what a small farm may print otherwise. In the example below, a 400-hen farm candles a morning's eggs. Below are the qualities, the sizes, candling, the example, and a free grading log.
The short version
- Two scales: quality (AA, A, B) and size (Peewee to Jumbo).
- AA: clean, practically normal shell; air cell 1/8 inch or less; firm white; yolk outline slightly defined.
- A: clean, practically normal shell; air cell 3/16 inch or less; reasonably firm white; yolk fairly well defined.
- B: an air cell past 3/16 inch, a weak white, a plainly visible yolk, or an abnormal shell.
- Sizes by net weight per dozen: Jumbo 30 oz, Extra Large 27, Large 24, Medium 21, Small 18, Peewee 15.
- A carton of U.S. Grade AA eggs at origin is at least 87% AA quality.
- The USDA grade shield means USDA graded them; your state's law covers other grade claims.
- TaroStack keeps each day's eggs as a lot with their grade and size. More below.
The qualities
| Factor | AA | A | B |
|---|---|---|---|
| Shell | Clean, unbroken, practically normal | Clean, unbroken, practically normal | Unbroken; may be abnormal or slightly stained |
| Air cell | 1/8 inch or less | 3/16 inch or less | Over 3/16 inch |
| White | Clear and firm | Clear and reasonably firm | Weak and watery |
| Yolk | Outline slightly defined, practically free from defects | Outline fairly well defined | Outline plainly visible; may be enlarged and flattened |
The air cell is the space at the large end of the egg; it grows as the egg ages, so a fresh egg candles AA more often. The full standards are USDA's Standards, Grades, and Weight Classes for Shell Eggs, AMS 56.
The sizes
| Size | Minimum net weight per dozen | Minimum for a single egg, at the rate per dozen |
|---|---|---|
| Jumbo | 30 oz | 29 oz |
| Extra Large | 27 oz | 26 oz |
| Large | 24 oz | 23 oz |
| Medium | 21 oz | 20 oz |
| Small | 18 oz | 17 oz |
| Peewee | 15 oz |
A dozen is sized by its total weight, and a single egg can weigh a little less than a twelfth of that, the third column. USDA's grades and standards page describes the voluntary grading service. This is general information, not legal advice; check your state's egg law before printing a grade.
Candling
In a dark room, hold each egg's large end to a bright light and turn it. You're looking at the air cell's depth, how the yolk moves and how clearly its outline shows, the shell's shape and cracks, and any blood or meat spots. Weigh each egg, or each dozen, for size. What goes on the carton besides the grade is in egg business license, and the date code in julian date code format.
An example: a morning's candling
Clover Hollow Farm, the made-up egg farm in Franklin, Tennessee, I use in these examples, candles and weighs a sample from each morning's collection:
| Egg | Weight | Air cell | White | Yolk | Shell | Quality | Size |
|---|---|---|---|---|---|---|---|
| 1 | 2.18 oz | 0.10 in | Firm | Slightly defined | Clean and normal | AA | Extra Large |
| 2 | 2.05 oz | 0.15 in | Reasonably firm | Fairly well defined | Clean and normal | A | Large |
| 3 | 2.45 oz | 0.12 in | Firm | Slightly defined | Clean and normal | AA | Jumbo |
| 4 | 1.95 oz | 0.22 in | Weak and watery | Plainly visible | Clean and normal | B | Large |
| 5 | 2.20 oz | 0.11 in | Firm | Slightly defined | Abnormal | B | Extra Large |
| 6 | 1.90 oz | 0.09 in | Firm | Slightly defined | Clean and normal | AA | Medium |
Egg 4 was an older egg missed in a nest box, which is why the farm collects twice a day. The B eggs go to the farm's own baking. How the eggs are priced is in how to price eggs.
Get the grading log
Download the egg grading log. Two sheets: a candling log that grades each egg AA, A or B from its air cell, white, yolk and shell and sizes it from its weight, with the share of AA; and a dozens sheet that sizes a carton from its net weight. It's an ordinary Excel file with no macros, and it works in Google Sheets, LibreOffice and Numbers.
Where this stops working
Every day's collection has its grades, sizes and pack date, and the grocers want Large and Extra Large, not whatever came in. A candling sheet doesn't say how many Large dozens are in the cooler, or how old they are.
How TaroStack does it
TaroStack keeps each day's eggs as a lot with their grade and size.
Each day a lot. A day's collection is a batch with a lot and its pack date, and fields of your own on the batch record hold the share of AA and the candling notes.
Sizes as items. Large, Extra Large and Jumbo dozens can be separate items, each with its own stock, so a grocer's order for Large comes from Large.
Oldest first. First-expired-first-out is the default, so the oldest lot goes out first.
| The job | Candling sheet | In TaroStack |
|---|---|---|
| A day's grade results | A sheet in a binder | Fields on the batch record |
| Large dozens in the cooler | Counted | Stock by item and lot |
| Which eggs go out first | Remembered | First-expired-first-out |
Lots, batches and expiry are on every plan, from $49 a month. The first 30 days are free, with no credit card. If you'd like a hand setting up, ask, and we'll do it with you.