Sunscreen Reapplication Planner
Enter your skin type, SPF, UV index and activity to get a personal reapplication schedule, a protection-time estimate, and how much sunscreen to apply each time.
- Enter your details and press Build My Schedule.
| Time | Action |
|---|---|
| Your schedule will appear here. | |
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Frequently Asked Questions (FAQ)
How is my sunscreen reapplication interval calculated?
The planner starts from dermatology guidance: reapply every 2 hours when dry, every 90 minutes with heavy sweating, and every 60 minutes when swimming. It then caps the interval at your theoretical SPF protection time, which is estimated from your skin type and the UV index, so the schedule never exceeds what your sunscreen can plausibly deliver.
How do skin type and UV index change the result?
Each Fitzpatrick skin type has a base unprotected burn time at UV index 3, from about 10 minutes for type I to about 90 minutes for type VI. The planner scales that base time by 3 divided by the UV index you enter, then multiplies by your SPF to estimate theoretical protection time. Higher UV index means a shorter window.
How is the sunscreen amount estimated?
The planner uses the laboratory standard of 2 mg of sunscreen per square centimetre of skin. It estimates your body surface area from your height and weight with the Mosteller formula, then multiplies by that standard. For face and neck only it uses a fixed area of 600 square centimetres.
Why do I still need to reapply if I use SPF 100?
SPF 100 blocks about 99 percent of UVB rays compared with about 97 percent for SPF 30, so the gain is small. Sweat, rubbing, water and UV itself break the film down, which is why dermatology bodies recommend the 2-hour reapplication rule no matter how high the SPF is.
Is this planner medical advice?
No. It is an estimate for information only, not medical advice. If you have a skin condition, take medication that increases sun sensitivity, or burn very easily, talk to a doctor or dermatologist about sun protection.