There is no definitive answer to the question of how many ETFs you should own, as this will depend on several different factors. For one thing, your personal investment goals and risk tolerance will play a major role in determining how many ETFs are right for you. Additionally, the size and diversification requirements of your portfolio will also impact which types of ETFs make sense for you to own. That said, a general rule of thumb is that a well-diversified portfolio should contain several different types of ETFs in order to maximize risk-return tradeoffs. Whether you are just starting out or have years of investment experience under your belt, it is important to conduct adequate research and take an informed approach when deciding how many ETFs you should own.