If you are a chest 32-34, the recommended size is S. If you are a chest 34-36, the recommended size is M. If you are chest 36-38, the recommended size is L. If you are chest 38-40, the recommended size is XL. If you are a chest 40-42, the recommended size is XXL.
Size Chart in Inches: (These are the garment ready measurements not body measurements)