His Old Norse textbook Altnordisches Elementarbuch remains a standard, and all literature concerning Gottfried von Strassburgs Tristan und Isold uses Ranke's line numbering for references to the text.

Graduating from the Katharineum at Lübeck, he studied German, English and Nordic philology at the universities of Göttingen (1902/03), Munich (1903/05) and Berlin (1905/07).

His term at the University of Strassburg produced his work of German folktales, Der Erloser in der Wiege; ein Beitrag zur Deutschen Volkssagenforschung ("The Redeemer in the cradle: a contribution towards German folktale research", 1911).

From 1912 Ranke was occupied as a tutor in Göttingen, After returning from his service at the front in World War I he was appointed assistant professor there in German philology, and then in 1921 full professor in German philology at the University of Königsberg; in 1930 he occupied the same position at the University of Breslau, whence, silenced by the Nazis in 1937, he removed to the University of Basel, Switzerland, as professor of German philology, where he remained until his death.

There are detailed accounts of Ranke, by Hartmut Freytag in Alken Bruns, ed.Lübecker Lebensläufe, (Neumünster: Karl Wachholtz Verlag) 1993, ISBN 3-529-02729-4, S. 317-320; and by Rolf-Wilhelm Brednich in Enzyklopädie des Märchens vol 11 (2004), pp203–207.