FlourScaleWhy egg size matters in baking
Most American recipes assume large eggs, which weigh about 50 g out of the shell according to King Arthur Baking. In a cake with three eggs, switching to medium eggs removes almost 20 g of liquid, fat and protein — enough to make the crumb drier and the cake slightly smaller. Converting by weight fixes that.
US egg sizes are defined by minimum weight per dozen (in the shell) under USDA standards: small 18 oz, medium 21 oz, large 24 oz, extra-large 27 oz and jumbo 30 oz. Shell accounts for roughly 12% of an egg's weight, so this calculator uses approximate out-of-shell weights of 37 g (small), 44 g (medium), 50 g (large), 56 g (extra-large) and 62 g (jumbo). Individual eggs vary, so for precise work crack them into a bowl and weigh.
Be careful with recipes from other countries: size names are not universal. A UK or EU "large" egg is heavier than a US large, and Australian grading is different again. When in doubt, use weight — around 50 g per egg is a safe default for most recipes.
Worked example
A recipe calls for 3 large eggs, but you have medium.
- Egg needed: 3 × 50 g = 150 g
- 150 ÷ 44 g = 3.4 medium eggs
- Use 3 medium eggs (132 g), then beat a fourth and add about 18 g of it
Egg substitutes and when they work
Eggs bind, leaven, add moisture and emulsify. No single substitute does everything, so choose one that matches the egg's main job in the recipe:
- Flax egg (1 tbsp ground flaxseed + 3 tbsp water, rested 10 minutes): a good binder for muffins, quick breads, cookies and brownies. Adds a nutty flavour.
- Aquafaba (about 3 tbsp chickpea can liquid per egg, or 2 tbsp per white): whips like egg white, so it suits meringues, macarons and light cakes.
- Applesauce, mashed banana or yogurt (about ¼ cup / 60 g per egg): add moisture and some binding to dense cakes and quick breads, but little lift. Banana adds flavour.
- Commercial egg replacers: follow the packet. Usually reliable in cookies and cakes.
Substitutes work best when a recipe uses one or two eggs. In recipes where eggs are the structure — custards, soufflés, angel food cake, choux pastry — substitutes rarely give the same result, and it is better to find a recipe designed to be egg-free.