I usually wear a large for comfort but am originally a medium. I sized up with the hopes of altering the dress if it came too big, since the reviews said to go 2 sizes up. And boyyy am I glad I did! The dress is amazing! NO ALTERATIONS NEEDED! I am 5’9 (tall girl friendly; drags on the floor) and weigh 170lbs (DD cup, slim waist, moderately thick thighs/hips). It’s like the dress was made on me, literally. Fits perfectly. Hope this helps. Definitely size up tho