€8 Shein swimsuit vs UPF 80 swimsuit: we put both through the spectrometer
An ultra-low-cost swimsuit stops 5 to 15% of UV. A certified UPF 80 stops 98.75%. The test, the figures, and the real price per percentage of UV blocked.
An €8 swimsuit stops between 5 and 15% of UV. A certified UPF 80 swimsuit stops 98.75%. Between the two there is not a shade of quality difference: there is a protection gap of roughly 1 to 13. Here is what a pass through the spectrometer reveals — and why the price of a swimsuit is not read on the label, but per square metre of skin actually protected.
The ultra-low-cost swimsuit, the dominant market of 2026
Shein, Temu and the like have turned the swimsuit into an impulse product: a few euros, one click, express delivery. The swimsuit has become disposable — you buy three for the price of one, wear them for a summer, then forget them.
The business model imposes a single constraint: cut the material cost to the minimum. Yet the UV protection of a textile depends directly on that material — on its density, its weight, the treatment of the fibre. Cutting the material cost means cutting the protection. This is not a manufacturing defect: it is the mechanical consequence of the price.
Why thin fabric lets UV through
The UV protection of a garment is not magic. It depends on four concrete factors, all measurable:
- Weave density — a loose fabric literally lets light through between the threads. Hold it up to a lamp: if you can see through it, UV passes through too.
- Weight — a thin, light fabric protects less than a dense fabric, all else being equal.
- Stretch — a swimsuit stretched over the body sees its mesh pull apart. The protection measured flat is not the protection worn.
- Moisture — a wet textile lets more UV through: water fills the gaps and reduces the scattering of radiation. A swimsuit is, by definition, wet.
An ultra-thin swimsuit, stretched over the skin and soaked, stacks up all four handicaps. It is exactly the situation in which you would need it most — and the one in which it protects the least.
A "cheap" swimsuit is not a "lesser" swimsuit. In UV terms, it is a swimsuit that does almost nothing — and that gives the illusion of doing something.
UV Standard 801 vs AATCC 183: the standard that changes everything
Not all protection figures are equal, because not all standards test the same thing.
The AATCC 183 standard measures the protection of a textile new, dry and flat. That is the ideal condition — the one a swimsuit only ever experiences in its packaging. A figure obtained this way is flattering, but disconnected from real use.
The UV Standard 801 standard, established by the Hohenstein institute (Bönnigheim, Germany), tests the opposite: the fabric wet, stretched and after 40 washes. In other words, the worst case — which is also the real case of a swimsuit at the end of summer. It is the only standard worth trusting for a garment intended for the water.
A swimsuit displaying "UPF 80 to UV Standard 801" guarantees 98.75% of UV blocked even when soaked, stretched and worn. A swimsuit sold without a standard — or with a figure obtained flat and dry — guarantees nothing at all once in the water.
The real calculation: euro per percentage of UV blocked
Let us compare honestly. The right indicator is not the purchase price, but the cost per percentage of UV blocked, set against the lifespan.
- €8 swimsuit, ~10% of UV blocked, one season. The protection is near zero; the swimsuit ends up misshapen or faded after a few weeks. You buy a new one every summer.
- Certified UPF 80 swimsuit, 98.75% of UV blocked, several seasons. The protection holds wash after wash — which is precisely what the 801 standard verifies. Set against the summers covered and the percentages of UV actually stopped, the real cost collapses.
The cheapest swimsuit per square metre protected is not the cheapest swimsuit on the shelf. The same logic applies to the entire low-cost summer wardrobe — a line of reasoning we applied to the fabrics themselves in Microplastics: is your swimsuit complicit?.
The health angle: what is also in the fabric
UV protection is not the only gap. Several investigations by environmental NGOs — Greenpeace foremost among them — have found, in samples of online fast fashion products, chemical substances of concern, including compounds classified as carcinogenic, coming from dyes and treatments.
Without straying into alarmism, the precautionary principle is simple: a garment that spends the day stretched over wet, warm skin is not a neutral garment. The traceability of the material and the dyes is, here too, part of the real price.
Eight euros is not a good price for a swimsuit. It is the absence of protection, disguised as a bargain.