I'd lost some weight so I needed a new belt.  First I ordered a large, based on my hip measurement.  It was too big, but I decided to keep it because some of my shorts & jeans ride lower on my hips than at my waist so I'd keep & wear with those.  So you'd think by just ordering the medium it would be perfect.  NOT.  Turns out that in my opinion these belts run large.  Yes, I lost some weight, but not 10 pounds is just not that much.  No I'm not a very "hippy" shape so that does not explain it either.  I've never worn a size small in my life - I'm on the tightest setting on the medium and it's still loose.  We'll see where I go from here.