So there seems to be a bit of confusion about the difference between the terms SPF and UPF so we thought we would try and clarify here. Sun Protection Factor (SPF) and Ultraviolet Protection Factor (UPF) are two different standards that measure the effectiveness of sun protection products. SPF is used for sunscreen, while UPF is used for sun protective fabrics. 

Here are some key differences between them: 

- SPF only measures the protection against UVB rays, which are the main cause of sunburn and skin cancer. UPF measures the protection against both UVA and UVB rays, which can also damage the skin and cause premature aging. 

- SPF is based on how much sunscreen is applied and how long it takes for the skin to redden under sun exposure. UPF is based on how much UV radiation passes through the fabric and reaches the skin. For example, a fabric with UPF 50 blocks 98% of UV rays, while a fabric with UPF 25 blocks 96% of UV rays. 

- Material with a UPF rating of 15 would allow 1/15th (6.7%) of ultraviolet radiation (UVR) passing through it, blocking 93.3% of UV. For a person with very fair skin, this may not provide an all-day protection, hence the importance to look for clothing items with UPF of 50 or 50+. 

- SPF can vary depending on the amount, frequency, and quality of sunscreen application, as well as the skin type, weather conditions, and activities of the user. UPF is more consistent and reliable, as it does not depend on these factors. 

- SPF needs to be reapplied every two hours or more often if sweating or swimming. UPF does not need to be reapplied, as it lasts for the lifetime of the garment. Therefore, UPF clothing can provide better and more convenient sun protection than SPF sunscreen. 

However, it is recommended to use both sunscreen and UPF clothing for optimal protection, especially for areas that are not covered by clothing. We hope this helps you understand the difference between UPF and SPF. ?