What Is UPF 50 Certification? Inside GoldenOur's UPF 50+ Real Lab Results

A UPF 50 rating isn't a design choice or a marketing claim. It's a lab result. Real UPF certification means a fabric has been tested by a third-party lab using standardized methods that measure exactly how much UV radiation passes through it. If a hat says "UPF 50" without that testing behind it, it's an estimate at best.

Here's what actually goes into getting a hat certified, and why it matters more than most shoppers realize.

What UPF Certification Actually Is

UPF stands for Ultraviolet Protection Factor. Certification is the process of sending fabric samples to an independent lab, where they're tested against standardized methods to measure how much UV radiation the fabric blocks, both UVA and UVB.

The result isn't a brand's opinion of its own product. It's a number generated by equipment that measures the actual UV transmission through the fabric.

The Testing Standards Behind a Real UPF Rating

Two testing standards matter here: AATCC TM183 and ASTM D6603.

AATCC TM183 is the actual test method. It measures the transmittance, or blocking, of erythemally weighted ultraviolet radiation through the fabric, meaning it captures exactly how much UV light gets through across both the UVA and UVB spectrums. ASTM D6603 is the labeling standard built on top of those results. It sets the rules for how a UPF number can be stated on a garment label in the United States, so the rating on a tag reflects a lab result rather than a brand's own language.

Both exist to remove guesswork from the equation. A hat tested to these standards has a verifiable rating. A hat that isn't tested has a label.

What Actually Happens During Testing

Fabric samples are measured using spectrophotometer equipment, which assesses how much UV light passes through the material across the UV spectrum, not just at a single wavelength. This is what separates real testing from a visual gut check like "this fabric feels tightly woven, so it's probably UPF 50."

GoldenOur's hats were tested as received, meaning unstretched and dry, exactly as the fabric arrives before any wear. Under AATCC TM183 methodology, testing is performed across multiple specimens per sample to calculate a mean UPF value, rather than relying on a single reading. Both of our colorways, Red and Cream, were tested and certified independently.

Why Certification Matters More Than It Sounds Like It Should

Here's the part most people don't know: a lot of hats on the market that say "UPF 50" have never been through this process. It's a self-reported claim, not a tested one. There's no requirement that a brand prove the number before printing it on a tag.

That gap is exactly why certification is worth talking about, not as a technical footnote, but as the actual line between a hat that protects you and a hat that just looks like it should.

What Our UPF 50+ Rating Actually Confirmed

GoldenOur's UPF 50 Sun Hat was independently tested to AATCC TM183 and ASTM D6603 and came back rated UPF 50+, the Excellent protection category, the highest tier a fabric can achieve. Our lab results confirm the hat blocks 99.9% of UVA and UVB radiation. That's not a marketing number. It's the confirmed result from our official test report.

Why Fabric Blend Affects the Result

Not all UPF 50 fabrics are built the same way, and what a hat is made of directly affects how it tests.

GoldenOur's hats are constructed from a blend of 80% cotton and 20% linen. That's a meaningfully different starting point than the synthetic microplastic-based fabrics a lot of "UPF" hats on the market are built from, and it's part of why we pursued formal certification rather than assuming the rating. Both of our colorways were tested and certified independently at UPF 50+, so the rating isn't tied to a single batch or dye lot.

Why I Pursued Third-Party Certification

I didn't want GoldenOur to be another brand claiming UPF 50 on a tag with nothing behind it. I've spent my career in luxury fashion and beauty, at Ralph Lauren, Marc Jacobs Beauty, and now through my own agency, Sloane, and quality claims that can't be verified never sat right with me.

So we tested. Real lab results, real standards, real numbers. Not because it's required, but because if I'm asking someone to trust a hat with their skin, I want the proof to back it up.

The Bottom Line

A UPF 50 label means very little on its own. A UPF 50+ label backed by AATCC TM183 and ASTM D6603 testing, verified at 99.9% UVA and UVB block, means something you can actually verify.

That's the standard GoldenOur is built on.

Shop the GoldenOur UPF 50+ Hat made with a cotton and linen blend. Independently tested. Never compromise on sun protection and style.