Quick answer

SPF40 means the sunscreen filters about 97.5% of UVB rays, offering reliable protection for daily commutes and office wear without the heavy feel of higher SPFs.

Why SPF40 is a practical daily choice

SPF40 blocks roughly 97.5% of UVB rays, which is only about 1% less than SPF50. For typical daily exposure—walking to the car, sitting by a window, or a lunch break outside—this difference is negligible. The real benefit is texture: SPF40 formulas often feel lighter and more hydrating, making them easier to wear every day under makeup.

The trade-off: not for extended outdoor activity

If you plan to spend hours at the beach, hiking, or exercising outdoors, SPF40 may not be enough. For those scenarios, a higher SPF (50+) with water resistance is recommended. SPF40 is best for incidental, daily sun exposure.

Frequently asked questions about SPF40 for daily wear

How much UVB protection does SPF40 actually give?

SPF40 filters about 97.5% of UVB rays. In comparison, SPF50 filters about 98%. The 0.5% difference is minor for short daily exposure but can matter during prolonged sun time. For daily commutes and office wear, SPF40 gives you nearly the same protection as SPF50 with a lighter feel.

Does SPF40 protect against UVA rays too?

SPF only measures UVB protection. For UVA protection, look for a broad-spectrum label or PA rating. Many Korean sunscreens, including MISSHA Glow Dewy, offer both SPF and PA protection (often PA++++). Check the label for broad-spectrum or PA+ symbols.

How much sunscreen should I apply for SPF40 to work?

Use about 1/4 teaspoon for your face and neck. Applying less reduces the SPF protection proportionally. For example, half the amount gives roughly SPF20 instead of SPF40. Measure with the two-finger method: squeeze a line of sunscreen along your index and middle fingers for each side of your face.

Do I need to reapply SPF40 during the day?

Yes. Sunscreen effectiveness fades after about two hours of total sun exposure. If you are indoors most of the day, one morning application may be enough, but reapply before going out for lunch or if you sit near a window. Set a midday reminder or use a cushion sunscreen for easy reapplication over makeup.

Product spotlight

  • Glow Dewy Hydrating Sunscreen SPF40+ 50ml (OTC): Glow Dewy Hydrating Sunscreen SPF40+ has a serum-like, watery texture with no white cast. This makes it ideal for daily wear under makeup because it absorbs quickly and leaves a dewy finish without looking chalky or greasy.

    Glow Dewy Hydrating Sunscreen SPF40+ 50ml (OTC)

    Glow Dewy Hydrating Sunscreen SPF40+ 50ml (OTC)