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SPF Ratings Explained: What They Really Mean For Your Skin

SPF Ratings Explained: What They Really Mean For Your Skin

What does SPF actually mean?

SPF stands for Sun Protection Factor. It's a measure of how well a sunscreen protects your skin from sunburn caused by UV radiation

But here's the truth: SPF doesn't block all UVB. It simply delays how quickly your skin would burn without it.

If it takes you 10 minutes to start burning without protection, SPF 30 (in theory) gives you 30 times longer — about 300 minutes — before the same damage occurs.

But real life doesn’t happen in a lab.

Firstly, UV radiation in an equatorial desert is very different to a lake in Scotland or the top of an Alpine mountain. The situation is always unique.

On top of that, what you're doing matters. Sweat, water, rubbing your skin, or not applying enough means you never get that full SPF rating. In fact, most people apply half of what’s needed — instantly halving the protection. That's why dermatologists always recommend SPF 30 or higher, and why we always say: don’t just apply it — reapply it.

SPF 15 vs SPF 30 vs SPF 50+: What’s the difference?

You’d think SPF 30 is twice as strong as SPF 15. It’s not.

  • SPF 15 blocks about 93% of UVB rays
  • SPF 30 blocks about 97%
  • SPF 50+ blocks around 98–99%

This is best shown as a chart. As you can see, there is only a very slight difference between SPF 30 and SPF 50. 

The extra 1–2% might not sound like much, but over a full day outdoors — especially if you're active or exposed to strong sun — that difference adds up. That extra percentage could be the difference between protection and damage.

And remember: SPF only covers UVB. To protect against UVA (which penetrates deeper, causes ageing and contributes to skin cancer), your sunscreen needs to be labelled as ‘broad spectrum’ or rated with UVA 5-star protection.

The problem with low SPF

A quick scroll down the sunscreen aisle shows loads of SPF 10 or SPF 15 products. They're cheap and common. But they’re not enough — especially if you’re outside for more than a few minutes, if you’re sweating, or if you’re wearing too little of it.

Why we only make SPF 30 and SPF 50+

We’re not a beauty brand. We don’t sell fluff. Our job is high performance protection.

That’s why every LifeJacket sunscreen is SPF 30 or SPF 50+ and rated UVA / UVA 5* — the highest level available in the UK. We’re here for people who want proper protection, not cosmetic promises. Every formula is non-greasy, sweat-resistant, and built for people who take life outside.

If you’re going to bother with SPF, you might as well use one that actually does the job.

Quick SPF tips you might not know

  • Use enough. Most adults need a full shot glass (roughly 30ml) for full-body coverage.
  • Reapply every 2 hours — or more often if you're in water or sweating.
  • Use SPF every day — not just on holiday. UV damage is year-round.
  • Don’t forget your ears, neck, scalp, hands, and behind your knees — the most commonly missed spots.
  • Check for 'broad spectrum' or the UVA rating to make sure you're protected from both UVA and UVB.
  • 5+ sunburns in your life doubles your skin cancer risk
  • 90% of skin cancer is preventable, mostly by protecting your skin from UV

Final word

SPF isn’t just about not burning. It’s about protecting the largest organ in your body — your skin — from long-term damage. Forget the low-SPF stuff. Choose SPF 30 or higher.

Apply it properly. Reapply it often. And wear it every single day if you can.