I always did 2 x the width of the space to be covered plus hems. You can get by with 1.5x the width to be covered if necessary.
The tabs in your photo look further apart than the tucks made at the top of curtains, but I suppose that they might be the same distance as the tucks to hang the curtains since there are no tucks at the top of these photos. On my drapes, the hangers are every 7 inches. I would think that an inch or so either way would probably work.