In summary: Choosing the right SPF is key to protecting your skin from sun damage, premature aging, and pigmentation. SPF (Sun Protection Factor) measures UVB protection: SPF 15 blocks 93%, SPF 30 blocks 97%, and SPF 50 blocks 98%. For most people, SPF 30 is ideal for everyday indoor and outdoor use, while SPF 50 is best for sensitive skin, prolonged sun exposure, or when using active ingredients like AHAs, BHAs, or retinoids. Reapplication every 2 hours, choosing a broad-spectrum formula, and checking expiry dates are just as important as the SPF number itself. While SPF in makeup can help, it’s not enough on its own—use a standalone sunscreen as your main protection and layer makeup with SPF on top. Consistency is key: daily application and regular reapplication make SPF an essential habit for healthy, protected skin.