Jackets should not fit snugly. You will want some room inside the jacket should a honey bee end up inside with you!
Small: 46"-48" chest (Fits most people 5'0"-5'7", 110-145lb)
Medium: 50"-52" chest (Fits most people 5'5"-5-9", 135-165lb)
Large: 54"-56" chest (Fits most people 5'8"-6'1", 155-200lb)
Extra Large: 58"-60" chest (Fits most people 6'+, 230lb+)
Extra Extra Large: 62"-64" chest (Fits most people 6'0"-6'5", 200-250lb)