What does SPF on a sunscreen bottle means and how much SPF is required for daily use?

SPF or Sun Protection Factor indicates the level of protection against UVB radiation.

Other than the visible light that we can see with our naked eye, the sun transmits UV radiation to the ground as well, which is invisible to us. 95% of these UV rays are UVA rays, with the remaining being UVB rays.

UV radiation causes ageing of the skin and also is a risk factor for the development of skin cancer.

A higher SPF does indicate a better protection against UVB radiation, however the higher you go, the smaller the difference in protection.

• SPF 15 – Filters out 93% of UVB
• SPF 30 – Filters out 97% of UVB
• SPF 50 – Filters out 98% of UVB
• SPF 100 – Filters out 99% of UVB

Generally, I recommend a SPF of at least 30. Sunscreen needs to be reapplied regularly, especially if outdoor activities are prolonged.

Choosing a sunscreen with good UVA protection is important too and this is indicated by the Protection Grade of UVA (PA rating) and it is indicated by the number of + signs. The more numbers of “+” in a sunscreen, the better it is in protecting against UVA radiation.

The SPF stands for Sun Protection Factor. It is a measure of the protection against UVB or ultraviolet B light only. If you develop a sunburn after 20 mins in the sun, using an SPF 10 sunscreen will protect you up to 200 mins before you develop a burn.

In practice, the amount of sunscreen applied is much less that the amount used during laboratory testing so the actual protection from using the sunscreen is less. Generally, we recommend an SPF of at least 30.

Besides UVB protection, do read the sunscreen labels to look for the protection against UVA too. It is important for the sunscreen to have both good UVA and UVB protection as UVA can also damage the skin.