Timer SPF: quanto dura la tua protezione solare?

How Long Does Sunscreen Really Protect You?

SPF (Sun Protection Factor) measures how much longer you can stay in the sun before burning compared to unprotected skin. SPF 30 means it takes 30 times longer to burn than with no sunscreen — in theory. Real-world protection is affected by application amount, UV intensity, sweating, and time.

Our SPF timer combines your natural burn time (based on Fitzpatrick skin type), the SPF level of your sunscreen, and the current UV index to estimate how long your protection will last before you need to reapply.

Understanding SPF Numbers

SPF 15 blocks about 93% of UVB rays. SPF 30 blocks 97%. SPF 50 blocks 98%. The difference between SPF 30 and SPF 100 is only about 2% more filtration — the bigger factor is applying enough and reapplying on time.

Frequently Asked Questions

Does SPF 100 last twice as long as SPF 50?

No. Higher SPF filters more UV per unit time, it doesn't extend duration proportionally. All sunscreen should be reapplied every 2 hours regardless of SPF number. The photostability of the formula breaks down over time.

How does UV index affect sunscreen duration?

Higher UV index means more intense radiation per minute. At UV 10, your base burn time is roughly half what it is at UV 5. This means sunscreen's effective protection window shrinks proportionally with UV intensity.

Can I mix SPF products for better protection?

No. Layering SPF 15 moisturizer with SPF 30 sunscreen doesn't give you SPF 45. You get roughly the protection of the higher SPF product. Use a single product with adequate SPF applied generously.