1. What is SPF Protection Time?

SPF (Sun Protection Factor) protection time estimates how long sunscreen will protect your skin from UVB rays before you start to burn, based on your skin's natural burn time without protection.

2. How Does the Calculator Work?

The calculator uses the SPF formula:

Where:

• \( base\_time \) — Time to burn without protection (minutes)
• \( spf \) — Sun Protection Factor (dimensionless)
• \( protection\_time \) — Estimated protection duration (minutes)

Explanation: The equation multiplies your natural burn time by the SPF rating to estimate protected sun exposure time.

3. Importance of SPF Calculation

Details: Proper calculation helps prevent sunburn, reduces skin damage risk, and guides sunscreen reapplication timing.

4. Using the Calculator

Tips: Enter your natural burn time (typically 10-30 minutes for fair skin) and the SPF of your sunscreen. All values must be valid (base_time > 0, spf ≥ 1).

5. Frequently Asked Questions (FAQ)

Q1: Is SPF protection time exact?
A: No, it's an estimate. Factors like sweating, swimming, and application thickness affect actual protection.

Q2: Should I reapply before the calculated time?
A: Yes, most experts recommend reapplying every 2 hours regardless of SPF.

Q3: Does higher SPF mean proportionally more protection?
A: No, SPF 30 blocks about 97% UVB, while SPF 50 blocks about 98%. The protection doesn't scale linearly.

Q4: What's a typical base time?
A: Fair skin often burns in 10-15 minutes, medium skin in 20-30 minutes, darker skin may take longer.

Q5: Does this account for UVA protection?
A: No, SPF only measures UVB protection. Look for "broad spectrum" sunscreens for UVA protection.