Skincare · 3 min read ·
What does the SPF number actually mean?
SPF 30 versus SPF 50, star ratings and UVA protection explained simply.
Quick answer: SPF measures protection from UVB burning. SPF 30 blocks about 97% of UVB and SPF 50 about 98%. In the UK, the UVA star rating shows protection against ageing UVA rays, so look for both.
SPF and UVB
The number refers to burning rays. The jump from 30 to 50 is small but worthwhile for fair or treated skin.
UVA stars
UK sunscreens may carry a UVA star rating, with five stars the highest. Broad-spectrum products protect against both.
How much
Most people apply half the tested amount, so use around half a teaspoon for face and neck.
Reapply
Every two hours outdoors and after swimming or sweating.
Common questions
Is SPF 15 enough?
For daily life most dermatology guidance recommends at least SPF 30.
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Written by the Skin Deep Aesthetics clinical team, 6 Carlisle Road, Derry. This article is general information, not medical advice. Book a consultation for advice about your own skin.
