Clothing provides the most convenient protection against UV radiation.  In contrast to sunscreen lotion, clothing is relatively cheap and does not rub off.  One may think that clothing can block UV radiation completely but in fact it may not.  The effectiveness of clothing in protection against UV radiation does depend on a number of factors.

There are a number of factors:
- Tightly woven or knitted fabrics have closer fibre structure and can block more UV radiation.  Thicker fabrics also block more UV radiation.
- Many dyes can absorb UV radiation and therefore darker colour clothing provides more protection.
- Over-stretched or worn out garments can allow more UV radiation to pass through their small pores.
- Wet clothing offers less protection as scattering of light will become less with the presence of water.
- Clothing treated with UV absorber additives during laundry can give better protection.

In recent years, the Ultraviolet Protection Factor (UPF) has been introduced as a measure of the protection against UV radiation provided by a piece of clothing.  The higher the UPF value, the better the protection against UV radiation offered by the clothing.  A garment with a UPF of 50 allows 1/50 of the UV radiation falling on the surface of the garment to pass through it.  In other words, it blocks 49/50 or 98% of the UV radiation.  Although the UPF is a useful indicator for choosing sun protective clothing, one should note that it has not been adopted as an international standard yet.