Here are the Youth T-shirt Size Specs -
Product Specifications
Body Length Body Width Sleeve Length
YXS 19 14 6.5
YS 20.5 15.5 6.75
YM 22 17 7
YL 23.5 18.5 7.25
YXL 25 20 7.5
How to measure:
BODY LENGTH: Lay garment flat (face down). Measure from center back neckline seam straight down to bottom of the front hem.
BODY WIDTH: Lay garment flat. 1" below the armhole flat measure the garment across the chest.
SLEEVE LENGTH: Lay garment flat(face down). Measure from center back neck to outer edge of shoulder seam, then along outer edge to sleeve end.