What size letterman jacket can fit a 12 year old boy?

A 12-year-old boy typically wears a letterman jacket in sizes ranging from youth large (L) to adult small (S), depending on his height and build. Youth large generally fits boys around 5'0" to 5'5" tall and weighing between 90 to 120 pounds. It's best to check specific brand sizing charts as they can vary. For the most accurate fit, measuring the boy's chest and comparing it to the jacket's size chart is recommended.