What the SPF and PA numbers on a sunscreen label actually tell you, beyond just "bigger is better"

What SPF actually measures versus what people often assume it measures

SPF specifically measures protection against UVB radiation, the wavelength primarily responsible for sunburn — it doesn't directly measure UVA protection, the wavelength more associated with long-term photoaging, which is why SPF alone doesn't tell the complete UV-protection story despite being the number most prominently featured on packaging.

What the PA rating specifically adds to the protection picture that SPF doesn't cover

The PA (Protection Grade of UVA) rating, expressed in plus symbols, specifically measures UVA protection level — meaning a complete picture of a sunscreen's broad-spectrum protection requires looking at both the SPF number and the PA rating together, since they measure genuinely different things rather than one being a subset or simplified version of the other.

Reading sunscreen labels for both ratings together rather than focusing only on the more prominent SPF number

Check both SPF and PA ratings when evaluating a sunscreen's actual broad-spectrum protection level, rather than assuming a high SPF number alone indicates comprehensive UV defense — a sunscreen with SPF50 but only PA++ provides less complete UVA protection than one with the same SPF but PA++++.

MISSHA All-around Safe Block Essence Sun SPF45 PA+++ 50ml — available on BuyBeautyKorea →