Pasta by the percentage
Like bread, pasta dough is easiest to scale as percentages of the flour. King Arthur's fresh pasta — 280 g of flour and 3 large eggs (150 g) — is about 54% egg. Keep the percentages and the calculator scales it to any number of servings.
Start from your eggs
Many cooks begin with the eggs they have. Weigh them out of the shell and the calculator works out the flour and salt to match: 150 g of eggs at King Arthur's 54% needs 280 g of flour. A large egg is about 50 g (King Arthur), but sizes vary — weighing is what makes it repeatable.
Egg, yolk and water doughs
Eggs are mostly water, so an egg dough's hydration counts the water inside them: a whole egg is 76.15% water and a yolk 52.31% (USDA FoodData Central). That's why a yolk-rich dough feels stiffer than the same weight of whole egg. King Arthur's fresh pasta works out at about 41% hydration.
Southern Italian shapes like orecchiette and cavatelli are often just semolina and water. America's Test Kitchen's version is 326 g of fine semolina to ⅔ cup (about 158 g) of warm water — about 48%.
Sources: King Arthur Baking, Fresh Pasta; King Arthur Baking, Golden Durum Pasta; America's Test Kitchen, Fresh Semolina Orecchiette; King Arthur Baking, Ingredient Weight Chart; USDA FoodData Central, Egg, whole, raw, fresh (FDC 171287); USDA FoodData Central, Egg, yolk, raw, fresh (FDC 172184). All sources and how we use them.