Question: what is the difference between uv and upf?
Answer: How does UPF differ from SPF? UPF measures the amount of UV radiation that can penetrate fabric and reach your skin. Sun Protection Factor, or SPF, is based on the time it takes for UV-exposed skin to redden; if you burn after 20 minutes, if used correctly, an SPF 15 sunscreen may protect your skin 15 times longer.