This question must be seriously important, because I get it frequently. It’s also important to Tootsie Roll Inc. They have compiled a review of the literature (including results of “licking machine” studies): bit.ly/TootsieLicking. Short answer, somewhere in the low hundreds of licks.
This question has been researched thoroughly by parties ranging from high school students to engineering doctorate students. Interestingly enough, results vary drastically. A licking machine (oh yeah, a licking machine!) developed at Purdue University took an average of 364 licks to get to the center of a Tootsie Pop. At the same institution, 20 individuals conducted the same experiment and averaged 252 licks to complete the task. Another licking machine, developed at the University of Michigan required 411 licks to reach the center of a Tootsie Pop; and a group of high school students from Swarthmore Schools averaged 144 licks to achieve the goal So, to answer your question: Getting to the center of a Tootsie Pop takes between 144 to 411 licks, depending on whether you are a teenager or a licking machine.