Sample size has always been one of the first design choices a medical device sponsor has to make for a clinical study. But the calculation of sample size is not the most straightforward process and often leaves clinical teams wondering which method to use. What is the appropriate sample size for my medical device study/survey? How can I provide justification for sample size in a medical device study? Can I use a sample size calculator for my clinical trial? These are the most common questions regarding sample size for medical device studies that Jón Ingi Bergsteinsson at SMART-TRIAL will try to answer in this article.