Does SPF factor matter?

Does SPF factor matter?

Tash Hagan

Short answer: Yes, SPF factor matters.

What does SPF actually mean?

SPF stands for Sun Protection Factor. It measures how well a sunscreen protects your skin from UVB rays, the type of ultraviolet radiation that causes sunburn.

Here’s how it works:

  • SPF 15 blocks about 93% of UVB rays
  • SPF 30 blocks about 97%
  • SPF 50 blocks about 98%
  • SPF 100 blocks about 99%

The difference between SPF 30 and SPF 50 is only about 1% more UVB protection, not double the protection.

So does higher SPF make a big difference?

For everyday use, SPF 30 is generally sufficient if applied correctly and reapplied every 2 hours. Stil's protection factor is SPF 30.

However, higher SPFs (SPF 50+) can be beneficial if:

  • You have fair or sensitive skin
  • You burn easily
  • You’re spending extended time outdoors
  • You’re at high altitude or near reflective surfaces (snow, water)

The most important factor: Application

No SPF works if you don’t use enough.

Most people apply only 25–50% of the recommended amount, which significantly reduces protection. Reapplication is just as important as SPF number.

Final Verdict

Yes, SPF factor matters but proper application, broad-spectrum coverage, and consistent daily use matter even more.

Back to blog
Stil Suncare bottle with orange text on a light gray background

Stil Daily Face SPF 30

Stil is your daily mineral sunscreen for sensitive skin (minus the white cast).

SHOP NOW

About the Founder

Tash Hagan is the founder of Stil Suncare. After more than a decade working in fashion and e-commerce (including a stint as Art Director at Boden) Tash turned her focus to skincare after years of managing Crohn's disease taught her just how much ingredients matter.

Frustrated by mainstream sunscreens that triggered her symptoms, she set out to create the mineral SPF she couldn't find on the shelf: gentle, naturally-formulated, and free from harsh chemicals. Stil was born from that search ,made for her, and for anyone else who needs suncare they can trust.

You can read more from Tash on LinkedIn where she shares her thoughts weekly on running a business for the first time in the suncare category.