A dermatologist revealed how much SPF you actually need to be protected from the sun

Many people assume SPF 30 is enough to keep them protected from the sun. After all, they know it's more powerful than the SPF 10, and it seems less intense than super high SPFs they see at the store.

But in reality, SPF 30 rarely offers people enough protection, according to New York City dermatologist Valerie Goldburt. If a person actually wants to be protected from the sun, they need to use SPF 50 - at the very least.

"SPF is the sunscreen's 'sun protection factor' and it specifically refers to UVB protection. That's the sunburn-producing rays," Goldburt told INSIDER. "It tells us what fraction of UVB rays reach the skin."

But why isn't SPF 30 enough?

In theory, SPF 30 should be enough. Because if you're a person who burns after 10 minutes of direct sunlight without sunscreen, SPF 30 should protect you for 30 times that amount, or 300 minutes.

"The catch is that this assumes a very specific amount that's applied equally on the skin," Goldburt said.

For SPF 30 to fully protect a person, they'd need to apply two milliliters of the sunscreen per squared centimeter of skin, or in other words, way more than they usually apply.

"Nobody puts it on like that. If you were actually to put on the amount that's required to get that true SPF, you would see that sunscreen layer on the skin," the expert explained.

SPF 50 or more is your best chance at protection.

People tend to apply sunscreen by "rubbing it in." But doing that actually means that they're wiping the sunscreen off, according to Goldburt.

"The amount they do put on ends up providing less protection than SPF would provide."

And so, Goldburt recommends people wear sunscreen with at least SPF 50, since they'll get at least a couple of hours of protection even if they put on a very small amount.