What does the number mean in the SPF on my sunblock? Have you ever wondered what the Number means relating to SPF on your Sunscreens and Sunblocks? Well the number is the amount of time that you would be able to be in the sun without getting red. Let’s say for example that it takes your skin 5 min in the sun to get red, if you wore a SPF 30 sunblock it would take 30 times longer or 150 min to get red. These estimates are not always exactly accurate and as a going rule you should re-apply every hour that you have direct sun exposure. For some sunblocks with “true” Broad Spectrum SPF Click here.