I first bought this in a L, but it was too big on me. The dress is actually a little stretchy, so I would follow your waist measurement for sizing (I followed my bust size and ended up having to size down, a M is still a little loose on me but the bust fits perfectly (37bust/29waist). I bought this dress for an upcoming trip and was worried the exchange couldn’t come on time and reached out to the customer service, and they were so quick and understanding with their reply! They even expedited the exchange process for me, I couldn’t be more thankful. The dress is so beautiful and heavy and feels so well-constructed, I couldn’t stop twirling in the dress LOL