Understanding your sunscreen label could protect your skin for life.
SPF 15? SPF 50? SPF 100?
If you’ve ever grabbed a bottle of sunscreen and wondered what does SPF mean, you’re not alone. It’s one of the most misunderstood parts of sun protection—and the truth may surprise you.
Here’s what those numbers actually tell you—and what they don’t.
SPF Is a Time-Based Measure
SPF stands for “Sun Protection Factor.” It measures how long the sunscreen protects your skin from UVB rays—the kind that cause sunburn.
Here’s a simple way to think about it:
- SPF 15 blocks about 93% of UVB rays
- SPF 30 blocks about 97%
- SPF 50 blocks about 98%
That means SPF 30 doesn’t offer double the protection of SPF 15. The difference in protection is just a few percentage points—so higher isn’t always better.
So… Can I Stay in the Sun Longer?
Not exactly. SPF numbers are based on ideal lab conditions, not real life. Sweat, water, and missed spots all reduce effectiveness.
To stay protected:
- Reapply sunscreen every 2 hours
- Use at least a shot glass–sized amount (1 oz)
- Apply 15 minutes before going outside
You Still Need Broad-Spectrum Coverage
SPF only covers UVB rays. But UVA rays—also from the sun—penetrate deeper into the skin and can cause premature aging and skin cancer.
To protect against both:
✅ Choose a broad-spectrum sunscreen
This ensures the product defends against UVA and UVB rays.
Callout: Quick SPF Facts
🧴 How much? 1 ounce (about a shot glass) per full-body application
⏱ When to reapply? Every 2 hours—or sooner if swimming or sweating
🌥 Cloudy days? Still need sunscreen—UV rays pass through clouds
💧 Waterproof? No sunscreen is waterproof—look for “water-resistant” and still reapply
What SPF Should You Actually Use?
Most dermatologists recommend using SPF 30 or higher for everyday use.
Unless you’re extremely fair-skinned, live at high altitude, or spend all day in direct sun, SPF 30 usually offers solid, reliable coverage—if applied and reapplied correctly.
Don’t Skip It—Even for Short Outings
You don’t have to be at the beach to get sun damage. Running errands, eating lunch outside, or walking the dog exposes you to UV rays that add up over time.
Even if you don’t burn, your skin is still being damaged. That’s why wearing sunscreen should be part of your everyday routine—just like brushing your teeth.
SPF Isn’t Everything—but It’s a Start
The SPF number isn’t magic. To really protect your skin, combine sunscreen with:
- Shade during peak sun hours (10 a.m. to 4 p.m.)
- Protective clothing and wide-brimmed hats
- UV-blocking sunglasses
And remember: sunscreen only works if you actually use it.
What This Means for You
Understanding what SPF means helps you pick the right sunscreen—and use it the right way. Choose SPF 30 or higher, reapply often, and make sun protection a daily habit. It’s one of the simplest ways to protect your health and your skin for years to come.
