SPF and the PA Rating System Explained

I bought a Korean sunscreen because it said SPF 50+ PA++++ and I assumed that was the maximum possible protection. It is — on the label. In practice, I was applying about half the amount used in the SPF test, which meant my SPF 50 was performing closer to SPF 7. The number on the bottle describes a laboratory condition. The number on my face described how much I squeezed out.

Korean sunscreens carry two ratings: SPF for UVB, PA for UVA. Both matter. Neither means what most people think. And the fact that different markets label UVA protection differently, or barely label it at all, is one of the genuinely important reasons to understand what you are reading on a Korean bottle versus an American one.

UVB and UVA: two different problems

UV type	Wavelength	What it does	What protects against it
UVB	280–315 nm	Burns the skin surface	SPF rating
UVA	315–400 nm	Penetrates deeper; ages skin and contributes to skin cancer risk	PA rating (Korea), UVA circle logo (EU), “broad spectrum” label (US)

A product can have a high SPF and poor UVA protection. That is why both ratings matter.

SPF: what the number means

SPF stands for Sun Protection Factor. It is measured by applying sunscreen to human volunteers at a density of 2 mg/cm² and then exposing the skin to UV until it reddens. The SPF is the ratio of the UV dose needed to cause reddening with sunscreen versus without.

• SPF 15 lets through about 6.7% of UVB.
• SPF 30 lets through about 3.3%.
• SPF 50 lets through about 2%.
• SPF 100 lets through about 1%.

The returns diminish rapidly above SPF 30. The AAD recommends SPF 30 or higher [5]. In Korea and the EU, labels are capped at SPF 50+, meaning the measured value was 60 or above. The reasoning: the marginal gain above 50 is so small that a higher number may mislead people into thinking they need less product or fewer reapplications.

The application gap

The critical caveat: SPF is tested at 2 mg/cm² of skin [1]. A review of real-world application found that most people apply 0.5–1.5 mg/cm², roughly a quarter to three-quarters of the tested amount [4]. At half the tested density, a product’s effective SPF is roughly its square root: SPF 50 applied too thinly performs more like SPF 7.

This is why dermatologists emphasize applying enough product and reapplying every two hours outdoors, rather than focusing on the highest possible SPF number [5].

A Korean sunscreen with a beautiful, lightweight texture that you apply generously because it feels pleasant is, in practice, likely to protect you better than a thick, chalky Western sunscreen that you apply in a thin, hesitant layer because you hate how it feels. Texture is not protection. But texture determines how much product makes it onto your face, and how much product makes it onto your face determines protection. Korean sunscreen textures are doing real work here, and it is not the work the marketing talks about.

The fair summary: SPF and PA are measured at 2 mg/cm². Most people apply half that. The number on the bottle is the ceiling, not the floor. Application amount and reapplication matter more than chasing a higher number.

PA: Korea’s UVA grading system

PA stands for Protection Grade of UVA and uses a scale of plus signs:

Grade	UVA Protection Factor (UVAPF)	Meaning
PA+	2 to < 4	Some UVA protection
PA++	4 to < 8	Moderate UVA protection
PA+++	8 to < 16	High UVA protection
PA++++	16 or higher	Very high UVA protection

Korea expanded the scale from three grades to four in 2016 [2]. Before that, the top grade was PA+++, which covered everything from UVAPF 8 upward, making it impossible to distinguish a factor of 8 from a factor of 30. The four-grade system is more informative but still groups everything above 16 together. Japan uses the same PA scale, so if you see PA++++ on a Japanese sunscreen, the grading means the same thing.

How different markets label UVA

Market	UVA label	What it tells you
Korea	PA+ to PA++++	Graded UVA protection factor
EU	UVA circle logo	UVAPF is at least one-third of the SPF (a ratio, not an absolute level)
US	“Broad spectrum”	Passes a UVA test (critical wavelength ≥ 370 nm), but no graded scale

A US “broad spectrum” sunscreen at SPF 30 may have much less UVA protection than a Korean SPF 50 PA++++ product. The labels are not directly comparable.

This is one of the regulatory differences that actually changes the answer for a consumer. In Korea and the EU, you can read the label and get a graded sense of UVA protection. In the US, you get a pass/fail. Whether the US system will adopt a graded UVA label has been discussed for years, and the FDA has not moved [6]. In the meantime, a Korean sunscreen label gives you more information about UVA protection than an American one. That is not an opinion about the products. It is a fact about the labels.

The independent testing question

Independent testing organizations have occasionally tested Korean sunscreens and found measured SPF values below the labeled rating. This is a real concern. SPF testing is done once, by or on behalf of the manufacturer, under controlled conditions. Independent retesting is rare and not required.

A beautiful texture is a reason to wear sunscreen. It is not evidence that the sunscreen works at the claimed level. If independent testing finds a product underperforms, the texture did not protect you. The number on the bottle is a test result from one test. Treat it as a starting point, not a guarantee, and apply generously regardless.

Comparing Korean sunscreens by both numbers

When choosing between Korean sunscreens:

1. Check both SPF and PA. SPF 50+ with PA++++ is the most protective combination available on the label.
2. Note the market. A product sold for the Korean market was tested under Korean standards. The same brand’s US version may have different filters and a different SPF.
3. Consider real-world use. A lighter product you apply generously and reapply may protect you better than a heavy one you underapply.
4. Don’t chase numbers beyond SPF 50. The practical difference between SPF 50 and SPF 100 is negligible compared with applying enough and reapplying.

There is also a behavioral concern. A randomized trial of 86 young adults on vacation found that those given high-SPF sunscreen spent significantly more time in the sun than those given a lower SPF, offsetting some of the extra protection [3]. The number gave them permission to stay out longer. The number did not give their skin permission to stay out longer. That gap is the behavioral risk of high SPF ratings: confidence outpaces coverage.

What to check on the label

1. SPF number. SPF 30 is the minimum most dermatologists recommend. SPF 50+ is the highest label claim permitted in Korea and the EU.
2. PA grade. PA++++ is the highest UVA grade available. If a product lists SPF but no PA grade, it may be a non-Korean product sold without UVA grading, or it may have been tested under a different standard.
3. Market of origin. A sunscreen labeled for the Korean market follows MFDS rules [6]. The same brand’s version sold in the US follows FDA rules and may use different filters. The bottle you are holding matters, not the one in the review.
4. UV filter list. Common Korean filters include ethylhexyl methoxycinnamate, bis-ethylhexyloxyphenol methoxyphenyl triazine and diethylamino hydroxybenzoyl hexyl benzoate. Some filters approved in Korea and the EU are not approved in the US. If you are buying a Korean sunscreen abroad, you are buying filters the FDA has not reviewed. That is a regulatory fact, not a safety judgment.
5. Water resistance. If claimed, the product was tested under water immersion conditions. Not all Korean sunscreens claim water resistance. Check before swimming or heavy sweating.
6. Expiry date and storage. Sunscreen filters degrade over time and with heat exposure. An expired sunscreen, or one that has spent a summer in a hot car, may not provide its labeled protection.

For more on how sunscreen fits into a complete routine, including how Korean and US sunscreen regulations differ, see our three-product K-beauty routine framework. For how sunscreen filter types affect texture and white cast, see chemical vs physical sunscreen in Korean products.

Now look at your sunscreen. Check both numbers: SPF and PA. If you only know the SPF, you are ignoring half the UV spectrum. Then measure how much you apply tomorrow morning — a full finger-length strip for the face, or about a quarter teaspoon. If that feels like a lot, you have been underapplying, and the SPF number on the bottle has been a polite fiction about your actual protection level.

Check both numbers. Apply the full amount. Reapply.

When to see a clinician first. See a dermatologist if you have a history of skin cancer, a photosensitive condition, or if you take medication that increases sun sensitivity. Sunscreen is one part of sun protection; shade, clothing and avoiding peak UV hours also matter. Seek urgent care for severe sunburn with blistering, fever or dizziness.