Start with SPF, but do not stop there
SPF stands for sun protection factor. It describes how well a sunscreen protects against UVB rays under standardized test conditions when applied as directed. UVB rays are a major cause of sunburn. A higher SPF indicates more UVB protection in that test, but it does not mean you can stay outdoors indefinitely or skip reapplication.
For everyday shopping, SPF is a useful comparison point, not a complete description of a product. Protection in real life also depends on how evenly and generously you apply it, whether you miss exposed areas, and what happens to the layer during the day. If you apply much less than the label directs, you should not expect the labeled level of protection.
Choose an SPF that suits your plans and any local guidance you follow. Whatever number you pick, check the rest of the label before deciding it is the right sunscreen for your routine.
Look for broad-spectrum protection
Sunlight includes both UVA and UVB rays. While SPF primarily describes protection against UVB, a broad-spectrum label indicates that the sunscreen also meets the applicable standard for UVA protection. UVA contributes to visible skin changes associated with sun exposure, so this wording matters even on days when avoiding a burn is not your only concern.
Broad spectrum does not mean that every wavelength is blocked completely. Labeling rules can also differ by country. If you shop across markets, you may see other UVA symbols or rating systems alongside SPF. Rather than assuming two unfamiliar labels are identical, read the package directions and look for a clear indication of both UVA and UVB protection.
A simple shopping checklist is to find the SPF, confirm broad-spectrum or equivalent UVA-and-UVB labeling, and then consider whether the texture works for you. A product you are comfortable applying as directed is more useful than one you routinely use too sparingly.
Understand water-resistance claims
Water resistant is a tested label claim, not a promise that sunscreen will stay in place all day. Where labels specify 40 or 80 minutes, that number refers to the period of protection demonstrated during water exposure under the relevant test conditions. It is especially worth checking if you expect to swim or sweat.
No sunscreen should be treated as waterproof. Follow the package directions for when to reapply, and put on more after swimming, heavy sweating or towel drying as directed. Rubbing your skin with a towel can remove some of the sunscreen layer even if the product is labeled water resistant.
For a mostly indoor day, water resistance may be less important than a finish you like wearing. For time at a pool, beach or outdoor workout, the stated water-resistance period becomes a more practical part of your choice. It does not replace the need to reapply.
Read the application directions, too
The front of the bottle is only a summary. Turn it over for directions about how much to apply, when to apply it and when to reapply. Some products need time before sun exposure; the label will tell you. Check the expiration date if one is provided, and follow storage instructions, particularly if the container may spend time in a hot car or direct sun.
Cover exposed skin evenly, including easy-to-miss areas such as ears, the back of the neck and the tops of feet when they are uncovered. Sunscreen in makeup can be convenient, but an SPF printed on foundation does not add to the SPF of a separate sunscreen. It also provides its labeled protection only when applied in the amount required by its directions, which may be more than you normally wear as makeup.
If a formula feels unpleasant or interferes with your routine, consider a different format rather than using an inadequate amount. Lotions, sticks and sprays can each be practical, but their application directions may differ. With a spray, pay particular attention to instructions about coverage and use near the face.
Put the label in context
Sunscreen is one part of planning for time outdoors. Shade, clothing, hats and sunglasses can help cover areas that are difficult to protect consistently with a product alone. The amount of exposure you expect matters: a short walk and an afternoon outside create different opportunities for sunscreen to wear off or be missed.
When comparing two products, ask three questions: Does the label indicate UVB and UVA protection? Is its water-resistance claim appropriate for the activity? Can I follow its application and reapplication directions comfortably? Those answers are more useful than choosing by the largest SPF number alone. Keep the package handy until its directions become familiar, especially when you switch products.
