What Does UPF Mean in Clothing?

UPF stands for Ultraviolet Protection Factor, a standardized rating that indicates how much UV radiation a fabric blocks. A garment with a UPF 50 rating allows just 2% of UV rays to penetrate—providing excellent protection against both UVA and UVB rays.

While SPF (Sun Protection Factor) applies to sunscreen and measures only UVB protection, UPF assesses textiles and evaluates protection from the full UV spectrum. Certified UPF clothing undergoes rigorous testing for UV transmittance under conditions like stretch, moisture, and post-wash exposure—factors that impact real-world performance.

A standard cotton T-shirt may offer only UPF 5 to 8, meaning up to 20% of UV rays can pass through, leaving your skin vulnerable. In contrast, purpose-built UPF fabrics use tight weaves, high-quality fibers, and UV-stable dyes or treatments to achieve UPF 50+ compliance.

How UPF Clothing Is Tested

Testing protocols for UPF rates are standardized under systems like ASTM D6603 and AATCC TM183. Fabric swatches are subjected to a UV light source, measuring the percentage of UVA and UVB rays transmitted through the material. Some tests also replicate wear, wash, stretch (wet and dry), and chlorine exposure to ensure long-term performance.

Only garments that block at least 98% of UV radiation are certified UPF 50+, while those blocking 93% achieve UPF 15, which is considered "good" protection.

Why UPF Clothing Matters

Even the best sunscreen is effective only if applied properly—most users apply too little, too unevenly, or forget to reapply. In contrast, UPF clothing offers consistent daily protection, eliminating the need for reapplication on covered parts of the body.

UPF fabrics offer broad-spectrum defense even in conditions when sunscreen might fail, making them a reliable base layer for everyday outdoor activity—whether commuting, gardening, or traveling.

At Some Sun, we believe sun protection should feel effortless—not just functional. Our elevated UPF 50+ collection combines luxurious, breathable fabrics with streamlined silhouettes you’ll want to wear every day. Each piece is designed for real life in the sun—from brunch to beach to boardroom—so you can prioritize skin health without compromising on style.

Summary

• UPF is a textile safety measure assessing total UV blockage—UPF 50 blocks at least 98% of UV radiation.
• Unlike SPF, UPF applies to clothing and includes both UVA and UVB protection.
• Certified UPF clothing offers a more reliable, consistent defense than sunscreen alone.