Thread sizes

I have several balls of Aunt Lydia's Giant Crochet, 400 yards, 100% Mercerized Cotton, ART. 150 and I am trying to determine the actual thread size. Is there a chart somewhere that tells you the size of various manufactures and types of of threads? Or does anyone know this information?

Forums: 

http://www.anniescatalog.com/yarn_and_thread/list.html?cat_id=1385&sourc...

Just type in the Search block on your box for sites about Thread/Yarn Co. sizes !
Mother Hen <><