DermUV
UV Index
The UV Index is a 0–11+ scale developed by the WHO and EPA that quantifies the strength of erythemally-weighted ultraviolet radiation reaching the Earth's surface.
UV Index explained
Each 1.0 of UV Index ≈ 25 mW/m² of erythemal UV. The scale is open-ended, but values above 11 are flagged 'Extreme' on every public dashboard. It is calculated from solar zenith angle, ozone column, altitude, surface albedo, and cloud cover. Most public providers update it hourly.
Related terms
Terms related to UV Index connect the UV and sunscreen topic cluster.
Related DermUV pages
Continue with calculators and city UV forecasts.