Question

What is the difference between SPF15 and SPF30? Is it double the protection?

Answer

An SPF30 does not provide double the protection. The difference is only in time. To demonstrate this difference, see chart below:

For example, if your skin starts to burn in 10 minutes without any sun protection an SPF15 gives you 15x10 or 150 minutes of protection. SPF30 gives you 30x10 or 300 minutes of protection (double the time of SPF15):

However, the amount of UVB rays that are absorbed is NOT double. It is calculated as follows:

SPF15 allows 1/15 or 6% of the UVB rays to get through to your skin, giving 94% UVB protection.

SPF30 allows 1/30 or 3% of the UVB rays to get through to the skin, giving you 97% UVB protection.

Ingredients To Look For In A Sunscreen

For UVA protection:

• Avobenzens
• Mexoryl SX
• Tinasorb
• Triazine

For UVB protection:

• Methyoxycinnamate
• Homosalate
• Octocrylene
• Sulfonic acid
• Tinosorb
• Triazine

Other ingredients:

• Titanium dioxide (absorbs and reflects UVA and UVB)
• Zinc oxide (reflects UVA and UVB)