Friday, 4 August 2017

How much sunscreen is 2mg/cm2?


How much sunscreen should I apply?

In previous article on Choosing The Best Sunscreen, we have mentioned that the SPF value stated on the sunscreen is actually based on the application as thick as 2mg/cm.

Ever wonder how much is 2mg/cm2?


I do. Let me measure my own face with a curve ruler. From forehead till chin 20cm, from ear to ear 26cm.

This is going to be a very rough figure. Although I'm a Virgo, I'm not very good at maths after leaving my mathematics class for years.

Surface area of a rectangle is Height x Width, then 20 x 26 = 520cm2.

If my face is a perfect oval, then the surface area will be 3.14 x 10 x 13 = 408.2cm2

I'm not good at maths, but the surface area of my face would be probably between 408 to 520cm given that he shape is between oval and rectangle?

To apply 2mg/cm2 to the face means I will need roughly 1040mg to cover the whole face = slightly more than 1g.

Say my 1 FTU = 0.4g, I need around 2.5 FTU of sunscreen to cover my whole face, not to mention neck and other areas.

To use this much of sunscreen, I probably have to apply layer by layer, let one layer dry and put on another layer. Else, I will look fairer than Geisha. Haha.

The other way of looking at whether I'm using enough sunscreen or not will be this: A 50g sunscreen will only be enough to be use for 50 times for me. Say that I apply twice a day, a 50g sunscreen will be used up in less than a month's time if I'm using according to the recommendation of 2cm/cm2!

This is exactly why we should buy the best sunscreen, the highest SPF, not just more than SPF35, because nobody use that much of sunscreen, and since we are under-applying, that little extra SPF protection, does make a difference.
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