{"title":"FDA — Sun Protection Factor (SPF)","entity_type":"Source","slug":"fda-sun-protection-factor","canonical_url":"https://skinknowledgebase.com/sources/fda-sun-protection-factor","dates":{"date_modified":"2026-05-09","date_reviewed":"2026-05-09"},"mcp_eligible":true,"evidence_sources":[],"product_fact_sources":[],"related_entities":[{"title":"EltaMD UV Clear Broad-Spectrum SPF 46","url":"https://skinknowledgebase.com/products/eltamd-uv-clear-spf-46"},{"title":"Photoallergic Contact Dermatitis from UV Filters","url":"https://skinknowledgebase.com/side-effects/photoallergic-contact-dermatitis-uv-filters"},{"title":"Avobenzone","url":"https://skinknowledgebase.com/ingredients/avobenzone"},{"title":"Titanium Dioxide","url":"https://skinknowledgebase.com/ingredients/titanium-dioxide"},{"title":"Zinc Oxide","url":"https://skinknowledgebase.com/ingredients/zinc-oxide"},{"title":"Sun Damage","url":"https://skinknowledgebase.com/concerns/sun-damage"},{"title":"What SPF should I use every day?","url":"https://skinknowledgebase.com/questions/what-spf-should-i-use-every-day"},{"title":"Does sunscreen actually prevent wrinkles?","url":"https://skinknowledgebase.com/questions/does-sunscreen-actually-prevent-wrinkles"},{"title":"Is mineral sunscreen better than chemical sunscreen?","url":"https://skinknowledgebase.com/questions/is-mineral-sunscreen-better-than-chemical-sunscreen"}],"body_sections":[{"heading":"Quick Summary","paragraphs":["A U.S. Food and Drug Administration explainer hosted by the Center for Drug Evaluation and Research that defines what the SPF number on a sunscreen label means. It walks through SPF as a measured ratio of UVB-burn protection, the diminishing-returns relationship between SPF number and percent UVB blocked, and the role of broad-spectrum labeling in extending protection to UVA."]},{"heading":"What Studied","paragraphs":["Not a study. This is the FDA's regulatory-authority definition page for the SPF metric. It describes how SPF is measured in controlled testing and what the resulting number does — and does not — convey about real-world sunscreen performance."]},{"heading":"Main Findings","paragraphs":["The page defines SPF as a measure of how much UVB radiation it takes to redden sunscreen-protected skin compared with unprotected skin. It states that SPF 15 blocks about 93% of UVB, SPF 30 about 97%, and SPF 50 about 98%, so the gain from raising SPF flattens fast. It clarifies that SPF measures UVB-burn protection only, and that \"broad-spectrum\" is the label cue indicating UVA coverage."]},{"heading":"Why It Matters","paragraphs":["This is the regulator-issued definition of the SPF number itself. For a Question explaining what SPF to wear every day, it provides the precise framing for \"SPF 30 vs SPF 50 — what's the difference?\" and for the broader point that the broad-spectrum label cue does more daily-wear work than chasing the highest SPF number."]}],"source_type":"regulatory","original_source_url":"https://www.fda.gov/about-fda/center-drug-evaluation-and-research-cder/sun-protection-factor-spf"}