bread recipes by weight

I assume you need to know how to convert volume measurements to weight/mass measurements?

If so, I have found these two sites helpful:

http://www.gourmetsleuth.com/cooking-conversions/calc.aspx

http://www.onlineconversion.com/weight_volume_cooking.htm

Just be careful about:

1. UK cups, Australian cups, and US cups are not the same. 
2. Check if the book, or author has a website to confirm what they mean by a "cup." Many cookbooks deliberately fudge the weight assuming their readers will measure wrong. Others use the "SPOON AND LEVEL" technique which usually tends to give too much. There is no use to knowing what the true weight "should" be if the author meant something else.
3. If a measure is given as (for example) 1 cup ((8oz) butter, multiply weight by 28.375 to get grams.
4. Be aware that ounces are not the same as fluid ounces. The first is weight, the second volume. For water, milk, etc no biggie, but again for example, 8 fluid ounces of dark corn syrup is 328g while 8 ounces is 227g.
5. Check nutrition labels, although they may only provide an approximation. So, if a serving is 1 cup (6oz.) your question is answerred.

Cheers