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Each toroid core has an A_sub_L value which is the inductance in mH for 1000 turns squared or nH per turn squared. You start out with the required inductance. Divide this value ( in nH) by A_sub_L to get the number of turns squared. Take the square root of the number of turns squared to get the number of turns.
Ferroxcube has a 950 page application handbook with all of the details for may ferrite transformers. http://www.ferroxcube.com/ select applications on the left menu and then the handbook link.