What Is SPF And How Does It Work

What Is SPF And How Does SPF Work?

  Sunscreen helps protect your skin from UV rays, which cause sunburn and the accumulation of cell-damaging free radicals. SPF is one aspect that determines the effectiveness of a sunscreen.

What does SPF mean?

SPF stands for Sun Protection Factor. It measures the level of UVB protection a sun protection product will give you and ranges from 4 to 50+. 

NIVEA Sun protection products also protect you from UVA rays.


The SPF indicates the length of time that your skin is protected from sunburn, depending on your skin type.

To help you understand a bit better, if you start getting sunburned after five minutes in the sun without any sunscreen, applying a sunscreen with an SPF of 30 would protect you for 30 x five minutes (or 150 minutes) before you begin to burn.

Depending on your skin type, location and the time of year, the time it takes for you to begin getting burned is between five to 30 minutes, on average.

There are some other factors that will also affect your level of protection, such as:

  • How much sunscreen you apply
  • The weather conditions
  • If you are wearing protective clothing, a hat, sunglasses
  • How much you sweat
  • How long you swim and how well you dry off afterwards
  • Your skin type

Women covering face from the sun


SPF 30 indicator in blue background

SPF 30 keeps out about 97% of the UVB rays and allows 3 photons out 100 through the skin. So, doubling the level of protection will block half the radiation that an SPF15 would.

SPF 15 indicator in blue background

SPF 15 will filter out approximately 93% of the UVB rays and allows 7 out of 100 photons through the skin If your skin would normally burn after 10 minutes in the sun, then applying and SPF15 sunscreen would allow you to stay in the sun for approximately 150 minutes without burning.

SPF 50 indicator in blue background

SPF50 and SPF50+ blocks out around 98% of the UVB rays and will block three times the radiation than an SPF15 sunscreen would let through your skin. Although, SPF50 AND 50+ still need to be applied liberally as with any other sunscreen.

As you know, sunscreens vary in SPF.

A high SPF extends the amount of time you can spend in the sun while protecting your skin. SPFs are broken down into four levels:

  1. Low (4, 6, 8, 10)
  2. Medium or Moderate (15, 20, 25)
  3. High (30, 40, 50)
  4. Very high (50+)

Sun care: choosing an ultraviolet sunscreen

We recommend using a sunscreen with an SPF 50+. No sunscreen can block all UVB rays. However, in terms of percentages, a sunscreen with these differences might seem small but over a lifetime, it all adds up and every little bit of protection helps.

A clock showing five minutes to two

When to reapply sunscreen

How often you need to re-apply sunscreen depends on the length of time you spend outside. If you spend all day in the office, the sunscreen you applied in the morning will not still be effective when you travel home at the end of the day.

If you are spending more time outside, remember to apply your SPF 50+ sunscreen just as regularly as your SPF 30 or SPF 15 to ensure continuous protection throughout the day. We recommend that you reapply sunscreen every two hours regardless of its SPF.

Always read the label. Follow the directions of use. Sunscreens are only one part of sun protection. Avoid prolonged high-risk sun exposure. Reapply frequently