You might have your skincare routine down to an art, but sunscreen is science. And while there’s so much to love about it, especially in a formula done well — such as our new Watermelon Glow Niacinamide Sunscreen SPF 50, which features an easy-to-blend, lightweight texture, a combo of physical and chemical actives, and supercharged ingredients like hyaluronic acid and niacinamide — sunscreen is still first and foremost a utilitarian product designed to protect your skin. (Without it, it’s just a moisturizer — just saying.)

For that reason, sunscreen has to stick to a few additional parameters than your average skincare product, including the stated levels of SPF. Here, we walk through the ins and outs of SPFs, how much you need, and how we ensured that you’re getting SPF 50 from this formula. (Spoiler alert: It involves tests.) Let’s get into it.

What does SPF even measure?

SPF, which stands for Sun Protection Factor, “is a measure of the time that it takes to make the skin red when wearing sunscreen compared to the amount of time required to develop a sunburn without wearing sunscreen,” says Marisa Garshick, M.D., a dermatologist in New York City. “Importantly, it specifically refers to the amount of protection against UVB radiation, the type of UV rays most responsible for developing a sunburn, and is not a measure of UVA protection.”

So, with SPF 50 applied properly, it would take 50 times longer for you to become burned than if you weren’t wearing any sunscreen at all. And again, it doesn’t measure UVA, which is what contributes to signs of aging (think dark spots and wrinkles) as well as skin cancer.

Why SPF testing is such a big deal

Drama is everywhere if you look for it — even in the sunscreen category. In fact, there’s been some controversy in recent years about sunscreen formulas not actually offering the level of SPF listed on the bottle. “As the FDA has proposed newer guidelines for sunscreen labels, the hope is there will be greater transparency for consumers to feel comfortable with the product they are selecting,” says Garshick.

To ensure our level of SPF aligned with our label, we put it through not one but two rounds of testing. The first is through the FDA, which is accepted in the United States and Canada. It entails critical wavelength testing, which means that 90 percent of the formula’s UV absorption occurs at a 370 nm wavelength. This test determined that our formula had an SPF of 59.

Next up? We sought out an international test called ISO, which is accepted in the European Union and calculates the SPF measurement through minimal erythema response. (Erythema is the reddening of skin — the more you know.) That test determined that our formula provided SPF 51.

Based on these tests, it made sense for us to call it SPF 50, which allows our formula to go above and beyond. And we’re sharing these results because we want to be transparent about the testing and decisions that went into creating this sunscreen. 

How much SPF do you really need?

The bare minimum, according to the American Academy of Dermatology, is SPF 30, which blocks 97% of UVB rays. However, “there is some added benefit to SPF 50 as SPF 50 blocks 98% of UVB rays,” says Garshick; meanwhile, SPF 30 protects skin from up to 97% of UV rays, and the incremental protection provided is super-small anything above SPF 50, like SPF 100. So, we wanted to create an SPF 50 to provide comprehensive daily protection that wears beautifully on skin.

Another downside of super-high SPFs, such as SPF 100, is that “it’s thought that products with high SPFs may offer a false sense of security and make people believe they can stay in the sun longer and may not reapply as often, or not necessarily commit to other sun protection strategies like seeking shade, which may in turn lead to a potential risk of sunburn,” she explains. In fact, the FDA has proposed capping the max SPF at SPF 60.

We believe SPF 50 is a sweet spot, since it’s higher than the recommended amount of coverage, but not so much that it could lull you into thinking you’re covered for an entire day at the beach. Ultimately, “aside from finding a product that is SPF 30 or higher, broad-spectrum, water-resistant when appropriate, the most important is finding one that you like and you will use,” says Garshick. With Watermelon Glow Niacinamide Sunscreen SPF 50, we sought to do just that — and hope it keeps you safe and healthy for many cloudy days, hot summers, and long weekends to come.

Read more about choosing a good SPF formula:

• Meet the Watermelon Glow Niacinamide Sunscreen SPF 50
• Why a Good SPF is Hard to Find
• Everything to Know about Sunscreen