I'm a big guy that usually wears XXL T-Shirts and Athleisure but these run a bit small so I went with the XXXL Swoveralls. They are a little snug when you first get them so do be aware that they stretch out a little as you wear them. For me this was a good thing as when I tried them on they were a bit tight and I was so sad they didn't fit but as I wore them throughout the day they stretched a bit to the perfect fit.