Understanding SPF: A Sunscreen Guide
Sunscreen is one of the most important parts of any skincare routine — dermatologists agree on that almost universally. But the labels can be genuinely confusing. SPF 30 vs 50? Broad spectrum? Mineral vs chemical? This guide cuts through the noise and explains what actually matters.
What Does SPF Actually Mean?
SPF stands for Sun Protection Factor. It's a number that tells you how well a sunscreen protects against UVB rays — the type of ultraviolet radiation most associated with sunburn.
Here's the simple way to think about it: SPF 30 blocks roughly 97% of UVB rays. SPF 50 blocks about 98%. SPF 100 blocks about 99%. The jump from 30 to 50 is meaningful. The jump from 50 to 100 is much smaller.
This is why most dermatologists recommend SPF 30 as the minimum — and why going much higher than 50 doesn't dramatically change the level of protection you're getting.
"The best sunscreen is the one you'll actually use every day. Finding one you enjoy wearing matters more than chasing the highest SPF number."
UVA vs UVB: Why Both Matter
The sun emits two main types of ultraviolet radiation that reach the skin: UVA and UVB. Understanding the difference helps you choose a sunscreen that protects against both.
These cause sunburn and are the rays that SPF numbers measure protection against. They're strongest during midday and in summer months.
These penetrate deeper into the skin and are present year-round — even on cloudy days. They play a role in skin aging and can contribute to skin damage over time.
This label means the sunscreen protects against both UVA and UVB rays. Always look for "broad spectrum" on the label — this is the gold standard.
Mineral vs Chemical Sunscreen
This is one of the most common points of confusion. Here's how the two types differ:
Mineral Sunscreen
Contains zinc oxide or titanium dioxide as the active ingredient. These minerals sit on top of the skin and physically block UV rays. Mineral sunscreens tend to be gentler — they're often recommended for sensitive skin. They can leave a white cast, though formulations have improved significantly in recent years.
Chemical Sunscreen
Contains ingredients like avobenzone, octinoxate, or oxybenzone. These are absorbed into the skin and work by converting UV rays into heat energy. Chemical sunscreens tend to be lighter and more invisible on the skin, but some people find them irritating — especially if they have sensitive skin.
Which Is Better?
Neither is universally "better." It depends on your skin type, your preferences, and what you'll actually stick with wearing daily. The best sunscreen is the one that feels good on your skin and that you reach for every morning without thinking twice.
How to Use Sunscreen Properly
Even the best sunscreen won't do much if it's not applied correctly. A few basics:
Use enough. Most people apply far less than they should. A generous amount — about a nickel-sized dollop for your face — is the target.
Apply it last. Sunscreen should go on after your skincare routine but before makeup. It needs to be on the outermost layer to work effectively.
Reapply. SPF protection doesn't last all day. If you're outdoors, reapply every two hours — or sooner if you've been swimming or sweating.
Don't forget easy-to-miss spots. Ears, the back of the neck, and the tops of hands all see sun exposure. A little extra there goes a long way.
"Sunscreen every morning — rain or shine, indoors or out. It's the single most consistent thing you can do for your skin's long-term health."
Final Thoughts
Sunscreen is foundational. It's the one skincare step that dermatologists, nutritionists, and skin health experts all agree on. Understanding what SPF means, choosing broad spectrum protection, and applying it consistently are the three things that matter most.
Don't overthink the SPF number beyond 30–50. Do think about whether you enjoy how the product feels — because the best sunscreen is genuinely the one you'll use. Every single day.