What Craig says in Reply 138 is especially true of flour and, to a lesser degree, water (in the sense that the variations in flour are typically greater than for water in my experience). What he says is also true of other ingredients, since one might measure out, say, a teaspoon of a particular ingredient, using a level teaspoon, a rounded teaspoon or a scant teaspoon. Each will produce a different result. If I need to convert a given volume of an ingredient to a weight, I will usually weigh a level teaspoon of the ingredient five times and take the average. In the various dough calculating tools on the forum, there are no conversions of flour, water or cake yeast to volume measurements. The rest of the conversions are based on government data, or conversions based on data found on labels, or weighings such as mentioned above. In some cases, as where there are many brands of an ingredient, I have sometimes taken the average of the multiple brands to use as conversion factors in the dough calculating tools.