As important as it is to develop feel and instinct when making dough, there is a metric formula for making pasta all'uovo. The Bolognesi love them. For every 100 grams of flour, use 1 50–55 gram egg (net weight, i.e., without the shell), which corresponds to 1 USDA medium egg. Your kitchen scale is almost certainly bilingual, and it is much easier to use the metric system for this than fractions of ounces, but it works out to 1 3/4 to 2 ounces of egg for every 3 1/2 ounces of flour.