Ranko was born in Belgrade, Serbia, where he attended Matematicka gimnazija and Petnica, and was a member of Arhimedes. From 1992, he spent 8 years at Oxford University, obtaining a BA in Mathematics and Computation (1994) and a DPhil in Computing (1999), and as a Junior Research Fellow. During that time, his colleges were University College, Merton College and Christ Church. At Warwick University, he has been a Lecturer (since 2001), Associate Professor (2006), Reader (2015), and Professor (2018).