I am 24 years old and weigh 165 lbs. 5'9. I usually go for a large boy size but after reading the reviews and seeing some people saying they were too big I decided to size down to a medium. The seat was tight but comfortable. I needed it to be tight because I was wearing it with a jumpsuit. So everything turned out perfect. Well if I made this shirt with jeans I would make a big one. Here's a little detailed review to help someone contemplating sizing as some of the reviews I've read have been helpful and some have not. Hope that helps.
Boys' Long-Sleeve Disney Star Wars Marvel T-Shirts by Spotted Zebra
46 Review
Kid Nation Kids' Tagless Long Sleeve V π Neck T-Shirts 4-12 Years - 2 Packs and 3 Packs
45 Review
Boys 3D Graphic Hawaiian Aloha Short Sleeve Dress Shirt Tops with Button Down - Sizes 2-8 Years by Uideazone
47 Review
The Good Day Lab Clean Shield: Ultimate Comfort and Breathability in Tagless 4-Way Stretch Polo
43 Review
Waterproof Cozy-Dry Rain/Snow Pants for π§ Kids by JAN & JUL, with Fleece Lining
64 Review
π Bold Pack Sleeve Active Hoodie Sweatshirt Set for Boys' Clothing - Stylish and Comfortable!
47 Review
Funny Guy Mugs Tearaway Sweatpants: Playful Boys' Clothing for Fun and Active Days
49 Review
π₯ Stay Warm and Active with Rocky Fleece Thermal Underwear Bottoms for Boys
44 Review