I would recommend taking a guess. After reading the reviews I ordered the XL for my average size 10 and they fit perfectly! He loves shirts and materials that speak volumes. Definitely great value for money!
Kid Nation Kids' Tagless Long Sleeve V 👕 Neck T-Shirts 4-12 Years - 2 Packs and 3 Packs
45 Review
Soft Brushed Fleece Crewneck Sweatshirt for 👕 Boys and Girls 4-12 Years - Kid Nation Kids
42 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 💧 Kids by JAN & JUL, with Fleece Lining
64 Review
🍉 Fruit of the Loom 6 Pair Cushion Ankle Boys' Clothing: Comfy and Stylish Selection for Active Boys
57 Review
🔥 Stay Warm and Active with Rocky Fleece Thermal Underwear Bottoms for Boys
44 Review
👖 Boys' Outdoor Climbing Convertible Trousers - Waterproof | Clothing
47 Review