I'm inspired by Bozenka's outfit done (in my tiny size) in warm or hot tie dye colors... I wish I could just post the pic.
www.youtube.com/watch

I would think a yard would do it if you were conservative. However, I would probably get a yard an a half to two yards, I'll always find a use for the leftovers...

Love, LOVE, Dharma Trading! Now I'm going to have to go look. Got their online newsletter yesterday but didn't look closely - have spent too much money with them recently. Arrrrrrgggggghhhhhhh!

The rule of thumb is from your nose to finger tip is about 1 yard.

Assume the fabric stretches in both directions or lengthwise (parallel to the selvages) only

If the fabric is 36" or wider, you'll have enough length for full length gloves or sleeves. So, measure around the largest part of your arm, add 2 or 3 inches. Now double that number, and that's about how many inches you'll need to make one pair of fitted sleeves or gloves.

If your arm is 11" around then add 2" = 13", doubled is 26", so you'd need at least 26" of 36" or wider fabric to make one pair of fitted sleeves or gloves. That's about 5/8 yd, and the pieces are cut with the top at one selvage and the bottom at the other.

If the stretch only goes crosswise (selvage to selvage), not lengthwise, you'll need to get at least 7/8 to 1 full yard for a set of full length sleeves or gloves. The selvage will parallel with the arm, up and down the glove.

1/2 yard of 36" or wider fabric should be enough to cover a bra, with extra scraps for headbands or small or ankle bands.

So if the stretch silk stretches in both directions and is 36" or wider, one full yard should give you plenty for a bra, one set of full length sleeves or gloves, and enough scraps for head and ankle bands.