Sizing Help

[Outlaw]

So I'm new to the forum and the world of swim briefs. I have always worn board shorts and I am now ready to buy my first pair of swim briefs, to wear under shorts and then possibly on their own for some lap and exercise swimming.

My question is what size do I need to order? I am looking at both Speedo brand and TYR, and briefs and square cut. In shorts, I wear a 30' but when I measured (one inch below the belly button) I was getting around 31-32. I want them to be snug, but not restricting.

Any help and/or advice will be greatly appreciated! Thanks!