How to determine your personal SPF number?


I came across a very useful article about our ideal SPF number based on our skin color.  According to Paula Begoun in her Beauty Bulletin, it is a multiplication figure based on your skin color and the SPF number on the product.

Your Level of Sunburn Risk x by the SPF Rating =
Safe Sun Exposure for Your Skin Color

The Beauty Bulletin article calculated SPF rating based on six levels of skin color. So for someone like me with fair skin color, I am at level 1, and my skin burns most easily amongst the six levels.  This means I need to use a sunscreen with a higher level of SPF rating because I’ll usually get a burn in about 15 to 20 minutes of unprotected sun exposure. 

SPF ratings for fair skin tone
SPF 15 x 20 minutes = 300 minutes (5 hours) of protection
SPF 30 x 20 minutes = 600 minutes (10 hours) of protection
SPF 45 x 20 minutes = 900 minutes (15 hours) of protection

So SPF 30 is just about good for me.  If you have darker skin color, please read the full bulletin here to find out how much protection you are getting with your current sunscreen.

SPF numbers only measure protection against UVB rays
A lot of times, consumers think that a higher SPF number means good protection. That’s only part of the story because the SPF number only measures the amount of protection from UVB rays or how long you are protected from burning.  SPF rating does not consider damage from UVA rays as I’ve written before about why SPF rating is not a good measure of sun protection.

Frequent application is still important
In addition, while the article tells you that you can get 10 hours of protection based on SPF30, it also depends if you’ve slapped on enough sunscreen on your skin.  Frequent application is still important especially if you’re out under the hot sun since some of the sunscreen ingredients may not be as photostable as claimed.


  1. pf1123 says:

    Quite difficult to reapply sunscreen during a day as I have makeup on. ?

  2. sesame says:

    It’s true…not practical to reapply but our sunscreens should be good enough for casual sun exposure. If outdoors, then need to re-apply. Oral intake of Heliocare is also effective.

  3. Cass says:

    i think the amount of sunblock we apply is also very important but dont know how to determine what is the right amount.

  4. loop says:

    Cute handmade pouches can be purchase from this website.

  5. aichaku says:

    oh i burn easily too… turn red just walking to the bus stop! thanks for the info on this. must read up more. ?

  6. pf1123 says:

    Is there such a calculation for PPD as well, being the measurement for UVA protection?

  7. sesame says:

    You should use about 1/4 to 1/3 tsp of sunscreen for the face. I wrote about it here and it also tells you how much to apply for the body.

  8. sesame says:

    Thanks for the link. Will have a look later.

  9. sesame says:

    You do? Mine, the last I remember when I did burn, only showed up hours later.

  10. sesame says:

    I haven’t come across but I believe PPD won’t apply so much for skin color, but rather across the board. So the higher, the better!

  11. Dee says:

    I burn first, then tan. Last time I was sitting on the bench with one of my arms exposed, my right arm became darker in 20 mins, lol.

    I’m a level 3, most of the time I don’t wear sunscreen on my body since I don’t wear short sleeve clothing much. only my face and neck since they’re always exposed and get tan fairly quick. But I should start huh? Nice article as always Sesame!

  12. sesame says:

    Good to get started on the body especially if you’re out on the beach esp cos our clothes give very low protection. I should have started earlier but heh, I’m a late learner!

  13. Becka says:

    Usually I’d applied a powder that contains spf during the day since at the same time it mattifies the shine away and I get an extra protection with the spf included from the face powder!

  14. sesame says:

    That’s what I do too – without the powder, the face is simply too shiny!

  15. knockingknees says:

    Not sure that powder with SPF actually makes a difference. I read somewhere that applying 2 products with SPF will actually reduce the efficiency of protection.

  16. sesame says:

    Reduce the level of protection? Oh that’s something of concern cause usually powder that we use contains SPF. What I know is that if you apply something over your sunscreen, you may reduce the effectiveness somewhat.

  17. sesame says:

    I just remember reading this from Paula Begoun’s Cosmetic Cop and she said: “What about applying foundation (one that doesn’t contain sunscreen) over the sunscreen you’ve just applied? That depends on several more factors, such as how much you apply, how thick or oily it is, or what kind of sunscreen you are using. To eliminate any dilution and to add more protection, you can choose to wear a foundation during the day that contains sunscreen. Voila, no more worries.”

  18. Carolyn says:

    This is a great blog post and such an important topic — I work with a company called Keys Soap, and co-founder and melanoma survivor Wendy Steel has an excellent related article on her blog that readers might want to take a look at, including tips, information and resources about skin safety and chemical-free skin protection sunblocks and other skincare products, plus a downloadable skin cancer awareness card. They can be found at:

  19. sesame says:

    Ah yes, I’ve used your sunscreen at one stage and liked it except for the nano bit.

  20. stiffedneck says:

    I read somewhere said with make up that has SPF in it, you have to apply 7 times as much make up of what you usually do to get that amount of protection claimed on the bottle. For example, if the bottle of foundation said SPF 15, apply 7 layers of foundation, then you get the actual SPF 15.

    And when you combine SPF 15 and SPF 30, you only get SPF 15. The protection goes with the lower number, not the combination of both. I don’t know why it works that way, but I remember its stated like that in some health mag.

  21. sesame says:

    I’m not sure about the 7 layers – first time reading this. But I do know you need to apply at least half a teaspoon of the lotion to get the full SPF. Perhaps that equals to about 7 layers?

    For the combination, I thought it was the higher one? I remember a dermatologist saying this at a workshop.

  22. Lina says:

    yesterday i went shopping with my friends, I applied sunblock with with spf 30 for my face and spf 24 for my body. but still it didn’t work. I got burn, and now tan (it’s only 40 minutes under the sun). And now i got confused what number of spf i should use…

  23. sesame says:

    It’s not just the numbers…you also got to check the active ingredients.

  24. hossein says:

    A tool for semi identifiable face is fat? Everyone does it so easily

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