I usually wear a 6. I ordered a 6 it was way too small. I returned it for 6.5 it was still small. Other than it runs small, the shoes are really well constructed and good workmanship. I returned it one more time for a 7.5 but it was then too big. My conclusion is that if you wear a 4 with Supadance, you probably need a 7 with this brand.
The description of this shoe said that all Bloch ballroom shoes run wide, and advised buyers to order 1/2 size down, so I ordered a 6.5 instead of 7. As soon as I got it out of the box I could see that it was tiny, and very narrow. My foot fit inside with some squeezing, but they were far too tight to consider dancing in, and my toes were completely squashed in the point. They looked like reasonably well-made and comfortable shoes (and are definitely pretty) but don't order half a size down! If I buy another pair after returning these, I'll probably even order a 7.5.
Another note - these don't come with heel covers, so you'll need to use some from another brand.