For most people, SPF 30 broad-spectrum sunscreen is the sweet spot. It blocks 97% of UVB rays, meets the American Academy of Dermatology’s minimum recommendation, and offers strong daily protection without the heavier feel of ultra-high SPF formulas. That said, the “right” sunscreen depends on how you spend your time outdoors, your skin tone, and whether you’ll be swimming or sweating.
What SPF Numbers Actually Mean
SPF measures how well a sunscreen filters UVB rays, the type that causes sunburn and contributes to skin cancer. The numbers aren’t linear, which trips people up. SPF 15 blocks 93% of UVB rays. SPF 30 blocks 97%. SPF 50 blocks 98%. The jump from 15 to 30 is meaningful, but the jump from 30 to 50 adds just one more percentage point of filtration.
That doesn’t mean higher SPFs are pointless, though. A study published in the Journal of the American Academy of Dermatology tested SPF 50 against SPF 100 on 55 people over five consecutive days at the beach. After five days, 56% of participants had more sunburn on the SPF 50 side of their body, compared to just 7% on the SPF 100 side. Sunburn first appeared on the SPF 50 side after one day of exposure, while the SPF 100 side didn’t show burns until day three. In real-world conditions where people under-apply and miss spots, higher SPF provides a bigger margin of error.
SPF 30 vs. SPF 50: Which to Choose
SPF 30 is enough for everyday activities like commuting, walking the dog, or running errands. If your sun exposure is incidental rather than intentional, SPF 30 broad-spectrum sunscreen does the job well.
SPF 50 or higher makes more sense when you’re spending extended time outdoors: beach days, hiking, yard work, outdoor sports. It also makes sense if you have very fair skin that burns easily, a history of skin cancer, or if you know you tend to apply sunscreen thinly (most people do). The extra percentage point of filtration on paper translates to noticeably better protection over hours of real use.
Broad-Spectrum Matters More Than SPF Alone
SPF only measures protection against UVB rays. UVA rays penetrate deeper into the skin, cause premature aging, and also contribute to skin cancer. A sunscreen labeled “broad-spectrum” has passed FDA testing showing it filters both UVA and UVB radiation. Specifically, the FDA requires a broad-spectrum sunscreen to protect across the UV spectrum up to at least 370 nanometers, which covers the UVA range.
Always look for “broad-spectrum” on the label. A high-SPF sunscreen that only blocks UVB is leaving you exposed to half the problem.
Your Skin Tone Still Matters
People with very fair skin that burns easily need SPF 30 or higher every day, no exceptions. The same goes for light to medium skin tones that burn before tanning. If you have darker skin that rarely or never burns, SPF 15 provides a reasonable baseline for daily use, though SPF 30 offers better protection against UV damage that doesn’t show up as a sunburn, including uneven pigmentation and long-term skin damage.
Regardless of skin tone, anyone spending prolonged time in direct sun benefits from SPF 30 or above.
Water Resistance Labels Explained
No sunscreen is waterproof. The FDA banned that term. Instead, water-resistant sunscreens are tested and labeled for either 40 minutes or 80 minutes of effectiveness while swimming or sweating. If the label says “water resistant (80 minutes),” it means the SPF holds up for 80 minutes in the water before you need to reapply.
If you’re going to the pool or beach, pick an 80-minute water-resistant formula. For general outdoor exercise where you’ll be sweating, 40 minutes is a reasonable starting point, but reapply as soon as you towel off or notice the sunscreen has worn away.
How Much to Apply (and How Often)
This is where most people lose their protection. To get the SPF listed on the bottle, you need about two tablespoons (a full shot glass) for your entire body. For your face alone, you need roughly a nickel-sized amount. Most people apply about a quarter to half of what’s needed, which is one reason higher-SPF sunscreens perform better in real life than the small percentage differences would suggest.
Reapply every two hours when you’re outdoors. Reapply immediately after swimming, sweating heavily, or toweling off, even if the two-hour mark hasn’t hit yet. If you’re working outside all day, set a reminder. Sunscreen doesn’t fail all at once, but its effectiveness fades steadily with time, UV exposure, and physical removal.
Check the Expiration Date
The FDA requires sunscreens to remain effective for at least three years from manufacturing. Most bottles carry an expiration date. If yours doesn’t, write the purchase date on the bottle and replace it after three years. Expired sunscreen can lose its protective ability, so digging out last decade’s beach bag bottle isn’t a safe bet.
What to Look for on the Label
- SPF 30 or higher for daily use, SPF 50+ for extended outdoor exposure
- Broad-spectrum to cover both UVA and UVB rays
- Water resistant (40 or 80 minutes) if you’ll be swimming or sweating
- An expiration date that hasn’t passed
Beyond those basics, the best sunscreen is the one you’ll actually wear consistently. If you hate the feel of a thick cream, try a lightweight lotion or a gel formula. If white residue bothers you, look for a tinted or chemical (as opposed to mineral) sunscreen. A perfectly formulated SPF 50 sitting in your bathroom cabinet protects you less than an SPF 30 you enjoy wearing every morning.