That's up for debate. In short, no not always. How often you use sunscreen and how much you use are more important than the SPF value. While SPF 15 is the FDA's minimum recommendation for protection against skin cancer and sunburn, the American Academy of Dermatology recommends choosing a sunscreen with an SPF of at least 30. https://www.skincancer.org/blog/ask-the-expert-does-a-high-spf-protect-my-skin-better/