You're probably using SPF wrong.

SPF ratings are tested at 2 mg/cm². For an adult face and neck that's roughly 1.2 grams — two full strips of product squeezed along your index and middle fingers. Body coverage is about a shot glass (30 mL) per full-body application.

SPF doesn't 'wear off' on a clock — it degrades through UV exposure, sweat, water, and physical rubbing (towels, hands, masks). Reapply every 2 hours when you're outdoors, and immediately after swimming or heavy sweating.

Indoors away from windows? One application in the morning is fine. Walking commute or near big windows? Reapply at lunch.

SPF 30 blocks ~97% of UVB. SPF 50 blocks ~98%. The marginal jump is small — what matters far more is whether you applied enough of it and reapplied on time. A correctly-dosed SPF 30 beats a thinly-spread SPF 100.

EU and Korean filters (Tinosorb, Uvinul) are widely considered the gold standard for elegance and UVA coverage; the US filter list is older and narrower.

1. 1

   Skipping ears, neckline, hands and your hair part

   These are exactly where skin cancer concentrates, because nobody covers them.
2. 2

   Layering moisturiser over un-set sunscreen

   Rubbing product over still-wet SPF physically smears the protective film. Let it sit 2–3 minutes.
3. 3

   Using last year's bottle past its PAO date

   The little open-jar icon (12M, 24M) is real — filters degrade. If it smells off or has separated, replace it.

UV filters are chemically active molecules — they don't stay potent forever. Once a bottle is opened, air, heat, and light slowly break them down, and the emulsion that holds mineral filters evenly suspended starts to separate. A degraded sunscreen doesn't just protect less; it can protect unevenly, giving you a false sense of coverage.

Rule of thumb: replace opened sunscreen after 12 months, or sooner if the label's PAO icon says less. Unopened bottles are good until the printed expiry date, usually 2–3 years from manufacture.

A fresh mid-range SPF beats a two-year-old luxury one every time. If you're using less than a bottle a season on your face, you're under-applying.

Dose and reapplication only happen if the product is wearable. The reasons people give for skipping SPF are almost always sensory — it feels greasy, it leaves a white cast, it stings the eyes, it breaks them out — or trust-related: they can't tell which recommendation was paid for.

We rate all of those explicitly, so you can filter on the objection that stops you.

Why people don't wear sunscreen — and what fixes each reason →