The two systems side by side
The USDA grades eggs by minimum weight per dozen, so each size is a floor, not a band. The EU grades by weight bands per individual egg. Put them together and the mismatch is obvious: a UK “large” is heavier than a US “large,” and a UK “medium” is the closest match to the American default.
| US size (USDA) | Min. per dozen | UK/EU size | Weight band per egg |
|---|---|---|---|
| Jumbo | 30 oz (850 g) | XL | 73 g and over |
| Extra-large | 27 oz (765 g) | Large | 63–73 g |
| Large | 24 oz (680 g) | Medium | 53–63 g |
| Medium | 21 oz (595 g) | Small | Under 53 g |
| Small | 18 oz (510 g) | — | — |
| Peewee | 15 oz (425 g) | — | — |
What this means for a recipe
An American cake recipe calling for 3 large eggs expects about 150 g of egg without shell (3 × 50 g). Baked with 3 UK large eggs, the same recipe gets about 180–200 g of egg — up to a third more liquid and fat. The cake may rise then sink, or stay damp in the middle. The reverse swap — UK recipe, US large eggs — gives a drier, tighter crumb. Neither failure looks like an egg problem, which is why it is so often misdiagnosed as an oven problem.
Substitution by weight, not by count
The reliable fix is to weigh eggs out of the shell. A standard US large egg gives about 50 g of edible egg; three of them give 150 g. To hit 150 g with medium eggs (about 44 g edible each), use three and a half — or four, and hold back a tablespoon of another liquid. For most home baking, the rule of thumb is: 4 medium = 3 large, and 3 medium = 2 large, with a tablespoon of milk added or withheld to compensate.
When size does not matter
Scrambled eggs, omelettes, frittatas and egg washes are forgiving — the cook adjusts by eye and the extra liquid cooks off. Size matters most in cakes, soufflés, custards, enriched breads and anything where eggs are the main liquid or the main structure. For those, weigh the eggs, and write the gram weight on the recipe card so the next bake is identical whatever size the box says.
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