Most of my measurements fit into one smaller dress size, but I was off a 1/2 inch in my hips and waist. I opted to buy the smaller size because I recently moved states and was off my typical diet and exercise programs. I am typically smaller but in my last month in my old state, I kept going out to eat because it was "the last time I could eat there for a while," and I was constantly skipping the gym to spend time with family and friends.
I am now back on track and even have a trainer. I texted my trainer from the bridal salon and asked her if I could lose 1/2 inch in my hips and waist in 6 months (I have no feel for measurements), and she said definitely! I actually have not lost any weight, but am getting measured again Thursday and am excited/nervous to see how far I've come.