Can you get sunburnt through a T-shirt?

Through a thin one, over enough hours at high UV, yes, it happens, particularly through wet fabric on a boat or at the beach. Through dense, dark or rated UPF fabric, effectively no.

Is a wet T-shirt worse than a dry one?

Considerably. Wetting typical cotton can cut its UPF by a third to a half, right when it's being worn for hours in full sun. A rated swim shirt keeps its protection wet, that's what it's for.

What should I look for when buying sun-protective clothing?

A UPF 50+ tag tested to AS 4399, dense weave, good coverage (collar, sleeves) and a fit you'll actually wear. For kids, one rashie outworks a summer's worth of sunscreen nagging.

Does UV go through clothes? What UPF ratings really mean

Yes, more than most people think. A typical light-coloured cotton T-shirt rates around UPF 5, meaning roughly a fifth of UV passes straight through the fabric. Stretched or wet, it can drop further. Clothing is still the most reliable sun protection there is, but only when the fabric is actually up to the job.

UPF: SPF's cousin for fabric

UPF, ultraviolet protection factor, measures how much UV a fabric blocks, tested in Australia under the AS 4399 standard. UPF 50 fabric lets through just 2% of UV; UPF 5 lets through 20%. Unlike sunscreen, fabric doesn't rub off, doesn't need reapplying and can't be under-applied, which is why every Australian authority puts 'Slip on clothing' first among the five S's.

Indicative values, actual protection depends on weave, condition and fit.
Fabric	Approximate UPF	UV transmitted
Typical white cotton tee	≈ 5	≈ 20%
The same tee, wet	≈ 3	≈ 30%+
Dark, densely woven cotton drill	20–40	2–5%
Denim	50+	< 2%
Rated UPF 50+ swim shirt (rashie)	50+	< 2%
Loose open-weave linen	3–10	10–30%

What makes fabric block UV

Weave density beats everything. Hold it up to a light globe, light through the weave means UV through the weave.
Colour helps. Darker and more vivid dyes absorb more UV than pale ones, all else equal.
Wet and stretched is worse. Water reduces scattering within fibres and stretching opens the weave, the damp tee worn swimming is the classic false security. For water, a rated rashie exists for exactly this reason.
Coverage counts. UPF 50 protects only the skin it covers: collars, longer sleeves and longer shorts move real estate from the 'sunscreen' column into the 'covered' column.

Do I still need sunscreen under clothes?

Under a dense or rated fabric, no; through UPF 50+ almost nothing arrives. Under a thin summer tee at UV 10, the 20% getting through equates to standing unprotected at UV 2, fine for an errand, meaningful over a full day outside. The practical rule: rated or dense fabric for long exposure, and sunscreen for the skin no clothing covers, face, neck, ears, hands.

Frequently asked questions

Can you get sunburnt through a T-shirt?: Through a thin one, over enough hours at high UV, yes, it happens, particularly through wet fabric on a boat or at the beach. Through dense, dark or rated UPF fabric, effectively no.
Is a wet T-shirt worse than a dry one?: Considerably. Wetting typical cotton can cut its UPF by a third to a half, right when it's being worn for hours in full sun. A rated swim shirt keeps its protection wet, that's what it's for.
What should I look for when buying sun-protective clothing?: A UPF 50+ tag tested to AS 4399, dense weave, good coverage (collar, sleeves) and a fit you'll actually wear. For kids, one rashie outworks a summer's worth of sunscreen nagging.

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