UPF 50+ explained
A UPF 50+ sun hat blocks at least 98% of the sun's UV rays, the highest sun protection rating a fabric can earn. Here's what UPF 50+ actually means, how it's tested, and how to spot a genuine UPF 50+ hat.
What is UPF (Ultraviolet Protection Factor)?
UPF stands for Ultraviolet Protection Factor. It's the international standard for rating how well a fabric blocks the sun's UV rays — both UVA and UVB. The higher the UPF, the less UV reaches your skin.
An average cotton t-shirt has a UPF of around 5, meaning roughly 1 in 5 UV rays still get through. A UPF 50+ hat lets less than 1 in 50 rays pass. That's at least 98% blocked.
What UPF 50+ means
98%+
of UV radiation blocked by the fabric. Only 1 in 50 rays gets through.
The UPF rating scale
Not all sun-protective fabrics are equal. The UPF scale tells you exactly how much UV passes through:
| UPF rating | UV blocked | Protection level |
|---|---|---|
| UPF 15 – 24 | 93.3 – 95.9% | Good |
| UPF 25 – 39 | 96.0 – 97.4% | Very good |
| UPF 40 – 50+ | 97.5% or more | Excellent — UPF 50+ |
UPF 50+ is the highest classification. Fabrics that exceed UPF 50 are marked "50+". This is the global maximum rating, only awarded after testing in an independent laboratory.
UPF vs SPF — what's the difference?
Both measure sun protection, but they protect different things in different ways:
UPF
Ultraviolet Protection Factor
Rates the protection of fabrics — sun hats, sun shirts, swimwear.
Blocks both UVA and UVB.
Doesn't wear off. Works all day.
SPF
Sun Protection Factor
Rates the protection of sunscreens applied to the skin.
Mainly measures UVB protection.
Needs reapplying every two hours.
A UPF 50+ sun hat and SPF sunscreen work best together. The hat is your physical barrier; sunscreen covers the skin a hat can't reach.
What makes a hat UPF 50+?
Three things decide whether a hat can legitimately carry the UPF 50+ label:
- Weave and fibre construction — a tight weave helps, but UV protection is not just about how solid the fabric looks. UV rays are absorbed, reflected and scattered by the fibres themselves. This means a fabric may let some visible light through while still blocking a very high percentage of UVA and UVB radiation.
- Fabric type and finish — synthetic fibres such as polyester often provide stronger UV protection than untreated cotton, but the final protection depends on the full fabric construction: fibre type, weave density, colour, stretch, moisture and any UV-inhibiting finish. Some natural materials, including tightly woven raffia or straw, can also perform very well when properly constructed and tested.
- Independent lab testing — the only reliable way to confirm UV protection is through laboratory testing with specialist equipment. A UPF 50+ claim should be based on testing under a recognised standard, such as AS/NZS 4399, ASTM/AATCC methods, or EN 13758.
The "hold it up to the light" myth
Many customers test a sun hat by holding it up to a lamp or the sun and worry when they see light passing through. This can be a useful rough check for obvious holes, loose weave or pinpricks of sunlight, but it is not a reliable UV test. Visible light and UV radiation are different parts of the spectrum. A UPF 50+ material can transmit some visible light while still blocking more than 98% of UVA and UVB radiation. The only accurate way to confirm this is through independent lab testing.
How to recognise a genuine UPF 50+ hat
A real UPF 50+ hat references one of these internationally recognised testing standards:
- UV Standard 801 — the strictest standard. Tests fabric in real-world conditions: stretched, wet, and after wear.
- AS/NZS 4399 — the Australian/New Zealand standard, widely seen as the global benchmark.
- EN 13758 — the European standard for UV-protective textiles.
Every sun hat we sell with the UPF 50+ label is tested by an independent laboratory under one of these standards. No claim without proof.
UVA vs UVB — what UPF protects against
The sun emits two types of UV radiation that reach your skin:
UVA
Longer wavelength. Penetrates deep into the skin (the dermis).
Causes premature ageing, wrinkles, and suppresses the immune system.
Present all day, all year — even through clouds and glass.
UVB
Shorter wavelength. Burns the top layer of the skin.
The main cause of sunburn and skin cancer.
Strongest between 10am and 4pm.
UPF rates protection against both UVA and UVB — that's what makes it a more complete measure than SPF, which is mainly a UVB rating.
Why a UPF 50+ hat matters
Skin cancer is one of the most common cancers worldwide. Most Western European countries sit in the global top 10 for skin cancer rates — the Netherlands ranks 5th. Cases in the Netherlands have doubled in the last decade, mostly caused by unprotected UV exposure.
A sun hat is a physical barrier between your skin and the sun. Unlike sunscreen, it doesn't wear off, doesn't need reapplying, and protects the parts of your face, scalp and neck that are hardest to cover.
Wide-brim styles extend the shadow further, covering shoulders and the upper back too. A UPF 50+ certified hat can be worn all day, every day — even on cloudy days, when up to 80% of UV still reaches the ground.
Sources: WCRF skin cancer statistics · KWF Kankerbestrijding · ECL Sun Safety Recommendations
