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 sunscreen will give you. In Australia and New Zealand the highest SPF rating is 50+. Sunscreen products in Australia also protect against UVA rays.


The SPF indicated the length of time that you skin is protected from sunburn. All skin types are different and have varying results from sun exposure. The SPF number is only a guide to it’s level of protection

Depending on you skin type, location and the time of year, the time it takes for you to begin getting burned is between 5 to 30 minutes on average.

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 SPF30 would protect you for 30 x five minutes (or 150 minutes) before you begin to burn

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 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 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 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.

In Australia our sunscreen standards have the following below levels

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

What SPF is best?

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

Always read the label. Follow the directions of use. Sunscreens are only one part of sun protection. Avoid prolonged high-risk sun exposure. We recommend that you reapply sunscreen every two hours or more often if necessary regardless of its SPF.