Comment on Why can't I apply SPF50 sunscreen twice to get SPF100 protection?

slazer2au@lemmy.world ⁨1⁩ ⁨week⁩ ago

SPF rating is subjective at best and not a regulated term in many countries.

Australia is a place where it is a regulated term and a test by Choice showed that 16 of 20 products failed their rating and several have since been recalled.
www.choice.com.au/…/sunscreen-test

Back to your original question which is answered in the article

In percentage figures that means the difference between, say, an SPF 50 sunscreen and an SPF 30 sunscreen is less impactful than you might assume. An SPF of 50 protects you from all but 1/50th of UV rays (98%), while sunscreen with an SPF of 30 protects you from all but 1/30th of UV rays (96.7%).

source
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