Sunbathing Calculator: Safe Sun Exposure Time by Skin Type

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The Fitzpatrick scale rates how your skin responds to UV radiation on a scale of I (most sensitive) to VI (least sensitive).
Current UV index at your location. Check a weather app or UV forecast site. Ranges from 0 (night) to 11+ (extreme tropical sun).
SPF 1 means no sunscreen. SPF 30 means the sunscreen blocks about 97% of UVB rays.
UV intensity increases by roughly 10-12% for every 1,000 m of altitude because there is less atmosphere to absorb the radiation.
Reflective surfaces bounce UV back onto you, effectively increasing exposure. Snow is the most extreme at up to 80% reflection.
Most people apply far less sunscreen than test conditions assume, so the real protection is roughly 50% of the SPF on the bottle.
Time to burn (unprotected)High UV - protection essential
27 min

How long you can be in the sun before your skin starts to redden without any sunscreen

Safe tanning window20 min
Time with your SPF27 min
Vitamin D time10 min
SPF needed for 8-hour day36
Effective UV index6.2
6.2 UV index
Low<3Moderate3-6High6-8Very High8-11Extreme11+

Your safe sunbathing window is 20 min at current conditions.

  • With Type II (fair) skin at UV index 6.2, your unprotected burn time is 27 min.
  • Stay under 20 min for gradual tanning without redness.
  • For roughly 1,000 IU of vitamin D, you need about 10 min of unprotected midday sun exposure with arms and legs bare.

Next stepApply sunscreen 15-30 minutes before going outside, reapply every 2 hours, wear protective clothing, and seek shade between 10 AM and 4 PM when UV is highest.

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