The alcohol by volume of Fernet is between 16% - 40%, and changes based on the production method or location where it is sold.
About the ingredients
Fernet: Fernet is an Italian type of amaro, a bitter, aromatic spirit. Fernet is made from a number of herbs and spices which vary according to the brand, but usually include myrrh, rhubarb, chamomile, cardamom, aloe, and especially saffron, with a base of distilled grape spirits. Fernet is usually served as a digestif after a meal but may also be served with coffee and espresso or mixed into coffee and espresso drinks. It typically contains 45% alcohol by volume. It may be served at room temperature or with ice. The Italian liqueur has a cult following in the international bartending community and is immensely popular in Argentina. The South American country consumes more than 75% of all fernet produced globally and, due to the product's popularity, also has Fratelli Branca's only distillery outside of Italy. As it is traditionally mixed with Coke, fernet has also contributed in making Argentina one of the biggest consumers of Coca-Cola in the world. Fernet and Coke (Spanish: fernet con coca) is so ubiquitous in Argentina that it has been described as "the country's unofficial drink".