I need the size to cut to make triangles
 

Please help ladies....to make two triangles sewed together to make a 5-1/2" block the way Jenny Doan does it....she sews a quarter inch around two squares and cuts and has 2 triangle blocks...do I make sense...what size would I start with...for it to come out a 5-1/2" block...thanks for all your help....I'm desperate...

Are you sure you want to make them that way? You end up with all your edges on the bias... Much better to cut 6.5" squares, mark a line in the middle and sew 1/4" on either side of your drawn line. Cut on the drawn line and square up. No bias edges to deal with.

If you do them the Jenny Doan way, make sure you starch your fabrics stiff that might help dealing with all that bias. I don't know what size to start with.
Personally I would probably do it the way Faintly Artistic suggested. jmho

A guess would be try squares of 8 - 8 1/4" using scraps (or even paper), may need trimming. You would get 4 HSTs. I agree with the starching before cutting.

There is a chart on this site for making hst two ways. The second method is the one you are looking for! Looks like 8.5 inch squares to get 5.5 inch hst.
I have found that sewing each side separately instead of around in a circle works better for me.
Good luck. Ann

http://www.blossomheartquilts.com/20...maths-formula/

This is is the way I do it (line down the center). And you end up with crisp, perfect HST's...

If you're going to be making a lot of HSTs, you may want to try making them with a grid, explained here. (It includes how to calculate the grid size.) This, like Faintly Artistic's method, puts the bias on the seam, not on the outer edges of the HSTs, which is usually preferable. So, you get the higher efficiency (fewer seams), but still avoid bias edges.

The math: (for 2 HSTs at a time, multiply the finished size you want by 2, then add 2" (many say 1 3/4" but easier to do 2" and trim).
So for a 5 1/2" block, cut a 13" square from each fabric. Draw diagonal line and sew 1/4" each side of line, then cut on drawn line. Makes 2 HSTs.

Google "making HSTs" and many tutes will be there.