Calculadora de Fator de Protetor Solar (FPS)
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
proteção = FPS × tempo_base; reaplicar a cada 2h independentemente
About this calculator
The Sun Protection Factor (SPF) Calculator estimates how long your skin is protected against UVB rays based on the SPF of the sunscreen you use. The calculation is simple: multiply the SPF by the time your skin takes to burn without protection. For example, if your skin burns in 10 minutes without sunscreen, an SPF 30 offers about 300 minutes (5 hours) of theoretical protection. Remember that this is an estimate, as factors like sweat, water contact, and improper reapplication reduce effectiveness.
Use this calculator when planning sun exposure, whether at the beach, pool, hiking, or outdoor activities. It helps determine when to reapply sunscreen and choose the appropriate SPF for your skin type and exposure time. Note that SPF only indicates protection against UVB, not UVA. For broad protection, choose broad-spectrum sunscreens and reapply every 2 hours or after heavy sweating or swimming.
Important precautions: the burn time without protection varies by skin phototype. Very fair skin burns in 5 to 10 minutes, while darker skin may take up to 30 minutes. The calculator considers this base time, but each person should know their own sensitivity. Also, never rely solely on SPF: wear a hat, sunglasses, and avoid sun between 10 a.m. and 4 p.m. Regular reapplication is essential, even on cloudy days.
Frequently asked questions
What does SPF 30 or SPF 50 mean?
SPF indicates the sun protection factor against UVB rays. SPF 30 blocks about 97% of UVB rays, while SPF 50 blocks approximately 98%. The difference is small but important for very sensitive skin.
Do I need to reapply sunscreen even if I don't go in the water?
Yes, reapplication every 2 hours is recommended even without water contact, as sweat and friction from clothing or towels reduce protection.
Is the calculated SPF the same for children?
No, children have more sensitive skin. A minimum SPF of 30 and more frequent reapplication are recommended. Consult a pediatrician for specific guidance.
Can I use the same sunscreen on my face and body?
Yes, but facial sunscreens usually have a lighter, less greasy texture. For the face, prefer specific products to avoid clogging pores.
Does expired sunscreen still work?
No, expired sunscreens lose effectiveness. Always check the expiration date and discard products after the date.