Sun protection factor is one data point, among many, when it comes to understanding the efficacy and safety of a sunscreen; along with its compatibility with your skin and lifestyle.

Our philosophy has always focused on simplifying the most complex aspects of skin care, to ensure you feel empowered to make clear choices about your own skin — so here is our simplified guide to reading any sunscreen label.

This is the number most of us look to first, and often the only factor we might consider. But it’s important to note that the sun protection factor only measures UVB, and the variances between each number may be more nominal than you think.

Analyzed as a percentage, SPF 15 protects against 93% of UVB rays; SPF 30 protects against 97%; and SPF 50 protects against 98%.¹ Doubling the SPF number does not double the protection. In fact, there is just a 1% difference between SPF 30 and 50 — and this number has no bearing on frequency of reapplication. No matter the SPF, it is advised that any sunscreen is reapplied every two hours. 

This is a crucial factor of any sunscreen formulation, which is often highlighted by dermatologists. The term broad spectrum indicates that a sunscreen provides defense against short and long-form UVA as well as UVB rays. 

In addition to the UVB protection indicated through the SPF rating, defense against UVA is essential. This longer wavelength is responsible for the majority of photoaging, has the ability to penetrate through cloud cover and windows, and is present at a consistent intensity year-round.²

A high SPF without a broad-spectrum designation is, by definition, incomplete protection.

This section lists out the filters used in the formula, which is one of the most consequential aspects of any sunscreen. 

Filters options are divided into two categories: mineral (zinc oxide, titanium dioxide) and chemical (avobenzone, oxybenzone, octinoxate, octocrylene, homosalate, among others). The choice between these shapes the formula’s tolerability on sensitive skin, photo-stability under UV exposure, and environmental footprint.

Zinc oxide is the only filter that provides standalone broad spectrum coverage. Inherently anti-inflammatory, it is the filter recommended by dermatologists for sensitive, reactive, and post-procedure skin.³ Every Tone SPF 30 is built on this zinc oxide alone, with no chemical co-actives.

The percentage of the active ingredient used in any sunscreen is an imperative factor. This concentration indicates the integrity of the formula, and how reliable it might be. Many formulas list zinc oxide but at a percentage too low to provide meaningful protection alone, relying instead on chemical co-actives or synthetic SPF boosters to lift the measured number to the labeled SPF.

Experts recommend a zinc concentration range of 15–20% to deliver meaningful broad-spectrum coverage.⁴ The Every Tone SPF 30 contains non-nano zinc at 17% to provide uncompromising, dermatologist-approved protection.

Often overlooked, the inactive ingredients fill in the gaps of any sunscreen story. This is where you often find the synthetic boosters hidden, even within formulas that announce themselves as “100% mineral.” These boosters inflate the SPF rating without having to raise the percentage of zinc in the actual formula.⁵ Some popular mineral sunscreens are formulated with as little as 4% zinc, despite many experts recommending a minimum of 10% for adequate protection.

In your ingredient list, look out for butyloctyl salicylate, tridecyl salicylate, and ethylhexyl methoxycrylene among others. These are all unregulated and many are questioned for their safety during pregnancy and compatibility with sensitive skin.

1. Wang, S. Q., & Lim, H. W. (Eds.). (2011). Principles and Practice of Photoprotection. Springer.

2. Matsumura, Y., & Ananthaswamy, H. N. (2004). Toxic effects of ultraviolet radiation on the skin. Toxicology and Applied Pharmacology, 195(3), 298–308.

3. American Academy of Dermatology. (2024).

4. Global Chemical. (n.d.). Zinc Oxide in Sunscreen.

5. Bloomberg. (2023, July 11). Mineral Sunscreens BOS Chemical Booster Draws Safety Concerns.