What do the PA plus signs on sunscreen actually mean?
SPF gets the big number on the front of the bottle, but on many sunscreens there is a second rating printed smaller: PA followed by one to four plus signs. It measures a different kind of ultraviolet light, and understanding it makes the SPF number easier to read too.
UVA and UVB are graded separately
Sunlight reaching skin contains UVB, the rays most tied to sunburn, and UVA, the longer rays that penetrate deeper and drive much of the visible aging of skin. SPF is built on a sunburn test, so it mostly reflects UVB protection. A sunscreen can post a high SPF while offering modest UVA protection, which is the gap the PA system was created to describe.
PA stands for Protection Grade of UVA. It originated in Japan and is now common across Asian markets and on imported products elsewhere. The scale runs from PA+ at the low end to PA++++ at the top, and it is based on how long protected skin takes to develop a sustained tan response compared with unprotected skin.
How the grades break down
The underlying measure is called PPD, persistent pigment darkening. PA+ means a PPD of roughly 2 to 4, PA++ covers about 4 to 8, PA+++ covers about 8 to 16, and PA++++ means a PPD of 16 or higher. In plain terms, each step up represents meaningfully stronger UVA protection, with the top grade reserved for the strongest formulas tested.
Most dermatology guidance for daily wear points to PA+++ or PA++++ when UVA exposure is a concern, paired with an SPF of 30 or more. For an ordinary indoor workday the difference between the top two grades matters little. For long outdoor days, driving, or bright climates, the higher grade earns its place.
What PA does not tell you
PA says nothing about water resistance, quantity needed, or how the product wears under makeup. It also is not used on United States drug fact labels, where the phrase broad spectrum is the regulated UVA signal instead, with no grades attached. Seeing PA on a bottle usually means the product was made for a market that uses the system, not that it passed an extra certification.
The grade also reflects a lab test at a standard application thickness that almost nobody matches in real life. Thin application lowers both SPF and UVA protection together. Two finger lengths for the face and neck remains the practical rule, whatever the plus signs promise.
Reading a label that shows both systems
When a bottle shows SPF and PA together, treat them as two halves of one picture: SPF for burn protection, PA for UVA depth. A balanced everyday product pairs SPF 30 to 50 with PA+++ or better. A very high SPF with only PA++ is a lopsided formula, strong on paper against sunburn and weaker where aging is concerned.
If a label shows neither PA nor broad spectrum language, that absence is information too. It usually means UVA protection was not tested or not a selling point for that market. For daily leave on protection, choose a product that accounts for both kinds of rays in some stated way.
Related reading
If this topic is useful, these earlier guides go deeper on connected questions: What does "mineral" on a sunscreen label actually mean?, What do cosmetic expiration symbols actually mean?, and What does "water-resistant" on a sunscreen label actually mean?.
Frequently asked questions
Is PA++++ always better than PA+++?
It indicates stronger measured UVA protection, yes. Whether the difference matters depends on exposure. For long outdoor days and bright climates the top grade is worth choosing. For a mostly indoor day, PA+++ with an adequate SPF is a reasonable and common recommendation.
Why do American sunscreens not show PA grades?
United States sunscreen labels follow the FDA drug facts format, which uses the term broad spectrum to signal UVA protection and does not grade its strength. The PA system comes from Japan and is used across much of Asia. The same formula can carry PA grades in one market and broad spectrum wording in another.
Does a high SPF mean high UVA protection too?
Not automatically. SPF is based mainly on UVB driven sunburn testing. Some high SPF products have only moderate UVA protection, which is exactly why systems like PA or the broad spectrum designation exist. Check for a UVA signal alongside the SPF number.
How much sunscreen do the PA ratings assume?
The tests use a standard thickness of 2 milligrams per square centimeter of skin, which works out to roughly two finger lengths of product for the face and neck. Applying less lowers real world protection below the labeled SPF and PA values, so quantity matters as much as the grade.