Alongside her apprenticeship as trainer and philologist she started a successful skiing career. In 1934 she won all titles at the German Championship. At the world championship in St. Moritz she won the slalom and the combined competition and was second in downhill (after Swiss Anny Rüegg). She won all titles at the world championships in 1937 (Chamonix ) and 1939 (Zakopane). To this day, Cranz remains the most successful competitor at Alpine World Skiing Championships with twelve gold and three silver medals.
At the 1936 Winter Olympics Cranz won the newly established alpine combined competition in a spectacular race. After a crash in the downhill competition Cranz was 19 seconds behind Laila Schou Nilsen (Norway), but after two outstanding slalom races she managed to win the combined ahead of Käthe Grasegger (Germany) and Schou Nilsen.
In 1943 Cranz married Adolf Borchers. After the end of the war she was arrested because of her collaboration with the Nazis and was forced to do farmwork for eleven months. Cranz fled into the American Occupation Zone in 1947. Later she founded a skiing school with her husband, which she led until 1987. Cranz was admitted to the Hall of Fame of International Women's Sports.
Cranz died at the age of ninety, in Oberstaufen-Steibis, Germany, in 2004.