Even there, I'm not too sure. I've found bread baking to be shockingly tolerant to variation— as long as I do 1tsp dried yeast per cup of water, and about 1.5 cups of water per loaf, it turns out beautifully. And if there's not enough yeast or it's rising slowly, whatever, just give it another hour to do its thing.

Anyway, that's across white, part whole wheat, part rye, and includes all kinds of additives like bran, wheat germ, cheese, herbs, roasted garlic, even tossing in a pot of leftover porridge from breakfast. Basic bread is almost impossible to screw up.