Pretty much a dozen egg whites of large eggs makes 1 1/2 cups.
So...6 would be 3/4 cup and 2 would be 1/4 cup....or pretty close.
Linda C

That's about right. Also, you can vary the amount of sugar. I have to do this since egg whites vary in size, too. After whipping the whites fully, I usually add the amount of sugar specified gradually, then check to see if it is stiff enough. The whipped whites with the incorporated sugar need to be very stiff to hold their shape in baking. If peaks are limp you will need to keep adding sugar. Thus you can adapt to the actual volume of your whites.