Enter your sunlight intensity, altitude, skin phototype, and SPF level to estimate your UV Index and calculate the maximum safe sun exposure time. You'll get a personalized sun protection recommendation, risk level, and suggested SPF — so you can enjoy the sun without the burn.
Estimated UV Index
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UV Risk Level
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Max Safe Sun Exposure
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Recommended Minimum SPF
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Protection Advice
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The UV Index (UVI) is an international standard measurement of the strength of ultraviolet (UV) radiation from the sun at a specific location and time. It ranges from 0 (no UV exposure) to 11+ (extreme). The higher the number, the faster unprotected skin can burn and the greater the risk of long-term damage like skin cancer.
A UV Index of 3–5 (moderate) is generally considered the safest range for tanning, as it allows gradual melanin production without rapid burning. At UV Index 6 or above, unprotected skin — especially fair skin types — can burn within minutes. Always apply sunscreen and limit exposure regardless of UV level.
UV intensity increases approximately 6% for every 1,000 metres (3,280 ft) of altitude. This is because thinner atmosphere at higher elevations absorbs less UV radiation. Skiers, hikers, and mountaineers are therefore at significantly higher risk of UV damage than people at sea level, even on cloudy days.
UV rays damage the DNA in skin cells. Repeated exposure causes cumulative damage that can lead to premature aging, cataracts, immune suppression, and skin cancer — including melanoma, one of the most dangerous forms of cancer. Each sunburn, especially in childhood, increases lifetime cancer risk significantly.
The Fitzpatrick scale classifies skin into five types (I–V) based on how it reacts to sun exposure. Type I (very pale) burns almost immediately and never tans, while Type V (dark brown) has more natural melanin protection and rarely burns. Knowing your type helps determine how long you can safely stay in the sun and what SPF you need.
Safe exposure time is estimated using the formula: Max Time (minutes) = (Skin Type Factor × SPF) / (UV Index × Altitude Factor × Reflective Surface Factor). A higher SPF and darker skin type extend safe time, while higher UV index, altitude, or reflective surfaces reduce it. This calculator handles all of that automatically.
SPF (Sun Protection Factor) indicates how much longer sunscreen lets you stay in the sun without burning compared to unprotected skin. SPF 15 blocks about 93% of UVB rays, SPF 30 blocks ~97%, and SPF 50 blocks ~98%. No sunscreen blocks 100% of UV rays, and reapplication every 2 hours is essential — especially after swimming or sweating.
Yes. Sand, snow, and water can reflect 80–90% of UV rays back at you, effectively nearly doubling your UV exposure. Even in the shade near these surfaces you can receive significant UV radiation. Concrete and pavement reflect around 25%, which is still meaningful. This calculator accounts for reflective surfaces in your safe time estimate.