Reading a sunscreen label: SPF, broad spectrum and the numbers that matter
SPF measures only part of the sun's damage. The word next to it decides whether you are protected against the rest.
Meridians Desk
Published 30 June 2026 · Updated 30 June 2026 · 5 min read
HealthThe short answer
- SPF indicates protection against UVB, the burning rays — it does not measure UVA, which drives ageing and deeper damage.
- Broad spectrum is the label term that signals meaningful UVA protection alongside the SPF number.
- Very high SPF numbers offer only marginally more protection than high ones, and can encourage under-application.
- How much you apply and how often you reapply matters more than squeezing out the last few SPF points.
A sunscreen label carries one number people fixate on and one phrase they ignore. The phrase is the more important of the two.
What SPF actually measures
SPF — sun protection factor — describes protection against UVB radiation, the part of sunlight mainly responsible for sunburn. It says nothing about UVA, which penetrates more deeply and drives skin ageing and other long-term damage. A high SPF with no UVA protection leaves a large gap.
Why ''broad spectrum'' is the word to find
Broad spectrum is the labelling term that indicates a product protects against UVA as well as UVB to a defined standard. Without it, the SPF number is only telling you about burning, not about the fuller range of damage.
Read the label as two pieces: a broad-spectrum claim for range, and an adequate SPF for strength. Then apply enough, and reapply — that is where most protection is won or lost.
Sources
Every factual claim above is traceable to these documents. Check them — that is why they are here.
- Sunscreen: how to help protect your skin from the sunUS Food and Drug Administration
- Ultraviolet (UV) radiation — questions and answersWorld Health Organization
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Meridians Desk is an editorial desk at Meridians, not an individual. A desk byline means the article was produced and fact-checked to that desk's published standards. Read our editorial standards and corrections policy.
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