Both (SPF/PA) are used to refer to the level of protection that skincare products provide against skin damage from UV radiation.

SPF (Sun Protection Factor) is a measure of how well sunscreen will protect the skin from damaging rays. For example, if your skin's natural protection time is 10 minutes, this time will be 150 minutes with a product with an SPF 15 protection factor.

The PA value (UVA Protection Level) represents the proportion of time taken for tanning. For example, if PA values are less than 2, "PA" is used as an indicator. If the PA value is between 4 and 8, the indicator is "PA++". The test methods for SPF and PA calculations are based on two international standards for in-vivo evaluation: ISO-24442 and ISO-24444. These methods irradiate human skin with UV from an artificial sunlight source with 2 mg or 2 μL of sunscreen applied per 1 cm2. The minimum time until redness occurs is evaluated for the skin areas where the cream is applied and where it is not. However, these test methods are costly, and individual differences can contribute to a subjective variation in results. That's why JASCO has developed a sunscreen SPF/PA rating system based on ISO standards. The system is used to calculate SPF and PA values from the transmittance spectra of sunscreens using a UV-visible spectrophotometer.

PA values are divided into 5 classes according to their PA equivalent values and labeled in accordance with their classes.

The following examples were measured using the parameters in the Measurement conditions table:

Labeled and calculated SPF and PA sample values