Published on August 05, 2019

kids sunscreen

What Does SPF Really Mean?

Sun Protection Factor (SPF) is defined as the scale used for rating the level of sunburn protection in sunscreen products. The higher the SPF of the sunscreen, the greater sunburn protection it gives to your skin.

True or False?

SPF = the amount of time you can stay in the sun and not get sunburned.

FALSE! Many consumers believe that SPF is related to the amount of time one is exposed to the sun.

SPF is related to the amount of sun exposure, not time.

SPF 30 sunscreen blocks 97% of the sun’s UVB rays. Higher SPF sunscreens block slightly more UVB rays, but no sunscreen can block 100 percent of UVB rays.


  • Intensity of the energy – For example, one hour in the sun at 9:00am may result in the same exposure to solar energy as 15 minutes in the sun at 1:00pm. This is because the sun is more intense at midday compared to other times of day.
  • Skin Type – People with lighter skin tones often burn more quickly and easily than those with darker tones.
  • Amount of sunscreen applied – According to the American Academy of Dermatology, most adults need 1oz of sunscreen, or enough to fill an espresso glass, to cover their full body with sunscreen.
  • How often you reapply sunscreen – It is recommended to reapply sunscreen every 2 hours or after swimming or sweating. Higher SPF sunscreen needs to be reapplied just as often as lower SPFs.


  • Broad spectrum (UVA and UVB ray protection)
  • SPF 30 or higher
  • Water resistant


  • Using sunscreen, staying in the shade, and wearing protective clothing all reduce your risk of skin damage and cancer.
  • All tanning damages your skin. There is no safe way to tan. This damage speeds up aging and increases skin cancer risk.
  • Even on cloudy days, 80 percent of harmful UV rays can damage your skin. Always wear sunscreen outside!
  • Skin cancer is often highly treatable if caught early. If you notice any changes in your skin, see a dermatologist.

Sources: National Cancer Institute. American Academy of Dermatology. The Health Tip of the Week is for educational purposes only. For additional information, consult your physician. Please feel free to copy and distribute this health resource.

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