After using the sizing guide and taking my measurements I was instructed to order a 22. However, having ordered and been fitted numerous times over the last several years for bridesmaid dresses I knew not to order this large. I always measure around 20-22 and have always ordered an 18. All of which have had to still be altered smaller in areas. I do know that material plays a part in sizing and fit. I had a size 18 chiffon dress in a similar style I had been fitted for and ordered from David's bridal approx 5yrs ago that I know had also been altered after order and it still fit. So, I took a risk, ordered the 18, and it fit like a glove other than the sleeves being a little tight under my arm pits and a little long. I am very happy with my purchase.