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Estimate safe sun exposure time with SPF recommendations by skin type and UV level.
The UV index is a standardized scale measuring the intensity of ultraviolet radiation. This calculator estimates safe sun exposure time based on UV index, skin type, and altitude.
| UV Index | Level | Protection |
|---|---|---|
| 0–2 | Low | Minimal needed |
| 3–5 | Moderate | SPF 30+, hat |
| 6–7 | High | SPF 30+, limit midday exposure |
| 8–10 | Very High | SPF 50+, avoid 10am–4pm sun |
| 11+ | Extreme | SPF 50+, stay in shade |
Formula
Safe Time (min) = MED / (UV_eff × 2.5), where UV_eff = UV × (1 + altitude/10,000)Safe Time = Minutes of unprotected sun exposure before erythema (sunburn)
MED = Minimal Erythemal Dose — varies by Fitzpatrick skin type
UV_eff = Effective UV index, adjusted for altitude
2.5 = Standard erythemal conversion factor
Worked Example
UV index 6, Skin Type II, sea level
Did you know? Australia has the highest rate of skin cancer in the world, with UV index values regularly exceeding 11. Their 'Slip-Slop-Slap' sun safety campaign has been running since 1981 (source: Cancer Council Australia).
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