I purchased one pair in size medium and one in large. I am a 5' tall female and normally about 135-140 lbs. But since becoming pregnant I gained weight and size, going up 1-2 pant sizes. The mediums still fit me very comfortably over my pants while working. I'm assuming I may need the larges for 3rd trimester. My biggest peeve is when coveralls/overalls are too snug, and I would say that these are perfect if you order the same size you usually wear in clothing sizes (I usually wear medium bottoms/pants, size 6 in most jeans pre-pregnancy)