Sun Protection

Spec Sheet

Broad Spectrum

In the US, a sunscreen can only be labeled 'Broad Spectrum' if it passes the FDA's critical wavelength test: measured on an in vitro spectrophotometer, the product must show a mean critical wavelength of at least 370 nanometers, meaning it absorbs UV radiation across the UVA range as well as UVB, not just UVB alone.

Comparison Table

SPF Rating Scale

SPF ratings measure UVB protection on a non-linear scale: SPF 15 blocks about 93% of UVB rays, SPF 30 blocks about 97%, and SPF 50 blocks about 98%. No sunscreen blocks 100% of UVB radiation, and the SPF number does not measure UVA protection or how long protection lasts in sunlight.