If you spend a lot of time outdoors, you’ve probably seen UPF 50 on sun shirts, swimwear, and other outdoor clothing. But what does UPF 50 actually mean—and how is it different from SPF?
For me, understanding UPF wasn’t just about choosing what to wear. It became part of the process of creating Agua y Sol.
What Does UPF 50 Mean?
UPF stands for Ultraviolet Protection Factor. It’s a rating system used to measure how much ultraviolet (UV) radiation passes through a fabric and reaches your skin.
A fabric rated UPF 50 allows approximately 1/50th—or 2%—of UV radiation to pass through, meaning it blocks about 98% of UV rays.
What's the Difference Between UPF and SPF?
Unlike SPF, which is primarily associated with sunscreen and protection from UVB rays, UPF ratings account for protection from both UVA and UVB radiation.
That’s why UPF clothing can be especially useful for people who spend long days outside, whether you’re swimming, hiking, paddling, traveling, working outdoors, or simply walking around in the sun.
What Makes Clothing Sun-Protective?
Not all clothing provides the same level of UV protection.
A fabric’s ability to block UV radiation can be influenced by several factors, including:
- Fiber type
- Density and construction of the fabric
- Color
- Stretch
- Moisture
- Wear over time
Generally, tightly constructed fabrics allow less UV radiation to pass through than loose, open-weave fabrics.
Polyester can provide strong UV protection when used in appropriately constructed performance fabrics. But fiber content alone doesn't automatically give a garment a specific UPF rating. A claim such as UPF 50 should be supported by testing of the finished fabric.
That distinction became important as Agua y Sol evolved.
If you're curious about polyester itself, we took a deeper look at what research says about polyester, textile chemicals, and fabric safety in our guide, Is Polyester Safe to Wear?
How My Search for Sun Protection Became Agua y Sol
Agua y Sol started in Bacalar, Mexico, where protecting the lagoon is part of everyday life.
Visitors are regularly encouraged to avoid wearing sunscreen in the water to reduce our impact on Bacalar's sensitive ecosystem, including its ancient microbialite communities.
I started researching alternatives and was encouraged by the idea that something as simple as the clothing we wear could provide another layer of sun protection.
For the first version of an Agua y Sol shirt, I researched which fibers and fabric constructions naturally offered greater UV protection. Polyester repeatedly stood out, so I chose a lightweight 100% polyester performance shirt designed to be quick-drying and comfortable in hot weather.
But I didn’t want to create another traditional rashguard.
Why I Chose a Relaxed Fit Instead of a Rashguard
Rashguards are great for swimming, but their tight, athletic fit can make them feel very specific to water activities.
I imagined something different: a sun-protective performance shirt people would actually want to keep wearing after they got out of the water.
Something you could paddle in at sunrise, walk through town in, travel in, or wear during an entire day outside.
That meant combining performance with a more relaxed, casual silhouette.
I also began working with artists to turn each shirt into something more than functional outdoor clothing. The designs became wearable art inspired by Mexico's wildlife, landscapes, and culture. You can view the collections by artist here.
The idea was simple: if we could make sun protection comfortable and beautiful and fun, maybe people would actually want to wear it.
From an Experiment to Hundreds of Shirts
The first shirts were, in many ways, a proof of concept.
Before investing heavily in custom textiles and manufacturing, I wanted to know whether people actually wanted what I was imagining.
They did.
After selling several hundred shirts, I knew it was time to invest in the next version of Agua y Sol—not just aesthetically, but technically.
I began searching for a highly reputable performance-textile manufacturer that could provide the quality and verified sun protection I wanted for the brand.
That’s when I found Lafayette and its Hydrotech performance fabric.
Why We Now Use Certified UPF 50 Fabric
Today’s Agua y Sol shirts are made with Lafayette Hydrotech, a performance textile with certified UPF 50 protection.
That means we’re no longer relying simply on what we know about polyester or the construction of a performance fabric. The fabric has been tested to verify its level of UV protection.
Hydrotech also gives us the performance qualities I wanted from the beginning: a lightweight feel, quick drying, moisture management, durability, and comfort for active days outdoors. Just as importantly, the base fabric is OEKO-TEX STANDARD 100 certified, meaning it has been tested for harmful substances, giving us another layer of confidence in a textile designed to be worn directly against your skin.
We paired the upgraded fabric with details such as a relaxed fit, flatlock-style construction, and thumb-holes to create a shirt designed to move between water, travel, town, and everyday life.
It represents how Agua y Sol has evolved: from a simple idea for an alternative to sunscreen in Bacalar into a thoughtfully designed piece of sun-protective clothing.
Does UPF Clothing Replace Sunscreen?
Not completely.
UPF clothing protects the skin it covers, which can reduce how much exposed skin needs sunscreen. Areas such as your face, neck, hands, and legs may still need additional sun protection depending on what you’re wearing.
A comprehensive approach to sun safety can include UPF clothing, shade, hats, sunglasses, and sunscreen on exposed skin.
For destinations where sunscreen use in the water is discouraged or restricted, protective clothing can also give travelers another option for covering more of their skin without constantly reapplying products.
Is UPF 50 Worth It?
If you spend significant time outdoors, UPF 50 clothing can make sun protection much easier.
There’s no need to remember to reapply protection underneath the fabric every couple of hours. You put the shirt on, and the fabric provides a physical barrier between your skin and UV radiation.
And for us, that’s really the philosophy behind Agua y Sol.
We don’t believe protecting yourself and caring for the places you explore have to compete with each other.
Protect your skin. Explore comfortably. And protect what you love.