A standard bed frame is normally made from 1 3/8'' x 1/8'' angle. But it is a high carbon alloy steel that is heat treated to about like a spring. The real question is: Why not just buy one? https://hollywoodbed.com/product-cat...ts/bed-frames/
https://www.amazon.com/s?k=bed+frame&ref=nb_sb_noss_1
But if you insist on making one, then I would go with the 2'' x 1/8 angle, the extra width to make up for the lack of heat treat.