SPF measures protection against UVB rays, the ones that cause sunburn, while PA measures protection against UVA rays, the ones that drive aging and pigmentation. The simple move is to choose a broad-spectrum sunscreen rated SPF 30 or higher with strong UVA coverage, shown as PA+++ or PA++++ where that label appears, and to apply enough of it, and reapply every two hours.
TL;DR:
- Choosing a broad-spectrum sunscreen rated SPF 30 or higher with PA+++ or PA++++ ensures balanced protection against both UVB and UVA rays.
- A higher SPF offers only marginal additional UVB filtration, but real-world protection drops significantly if the sunscreen is applied thinly or infrequently.
- PA ratings provide a more granular measure of UVA protection, with PA++++ indicating a PPD of 16 or higher, common on Korean and Japanese sunscreens.
- Consumers should reapply sunscreen every two hours, especially after water exposure or sweating, to maintain its effective protection.
- U.S. labels specify broad-spectrum status, while imported products often use PA ratings for UVA strength, so checking both helps clarify overall protection.
Table of Contents
- SPF vs PA at a Glance
- What SPF Measures and How to Read the Numbers
- What PA and PPD Measure, and Why UVA Protection Matters
- Reading U.S. and Imported Labels Side by Side
- Which Rating to Prioritize and a Simple Rule for Choosing
- Application Mistakes That Quietly Undo Your Protection
- How We Think About UVA and UVB Protection When Curating Sunscreens
- Start With a Balanced SPF and PA Combination
- FAQ
- Sources
SPF vs PA at a Glance
SPF and PA are not competing scales. They measure two different parts of the ultraviolet spectrum, and a sunscreen needs to perform well on both to earn a spot in your routine. UVB rays sit in the 290 to 320 nanometer range and cause sunburn, while UVA rays span 320 to 400 nanometers and reach deeper into the skin. SPF tracks the first. PA tracks the second.
| Rating | What it measures | Range | What it signals |
|---|---|---|---|
| SPF 15 | UVB protection | Blocks about 93% of UVB | Minimum everyday protection |
| SPF 30 | UVB protection | Blocks about 97% of UVB | Dermatologist-recommended baseline |
| SPF 50 | UVB protection | Blocks about 98% of UVB | Marginal gain over SPF 30 |
| PA+ to PA++++ | UVA protection | PPD 2 to 16+ | Tiered UVA strength, common on Korean and Japanese labels |
Here is what this means when you are standing in front of a shelf or scrolling a product page:
- Check for “broad spectrum” first. This phrase, regulated by the FDA, tells you a product has passed testing for both UVB and UVA protection.
- Treat SPF 30 as the floor, not the ceiling. Going from SPF 30 to SPF 50 buys you a small amount of extra UVB filtering.
- Look for PA+++ or PA++++ on imported products. These marks give you a UVA strength reading that U.S. labels usually skip.
- Never assume a high SPF number means high UVA protection. The two scales are independent, so a sunscreen can score well on one and poorly on the other.
What SPF Measures and How to Read the Numbers
SPF stands for Sun Protection Factor, and it is calculated through a test that measures how long skin protected by a product takes to show a minimal sunburn response compared to unprotected skin. Labs apply the product at a fixed rate and expose skin to UV light until reaching what researchers call the minimal erythema dose, then compare the protected and unprotected results to calculate the factor.
SPF 15 filters about 93% of UVB rays, SPF 30 filters about 97%, and SPF 50 filters about 98%. The jump from SPF 30 to SPF 50 sounds significant, but in practical terms it closes a small remaining gap rather than doubling your protection. This is why dermatologists tend to frame SPF 50 as a modest upgrade rather than a different category of defense.
There is a catch that matters more than the number itself. Lab testing applies sunscreen at a standardized rate of 2 mg/cm², but most people apply only 20% to 50% of that amount in daily life, which meaningfully cuts the real-world protection below the number printed on the bottle. A sunscreen labeled SPF 50 applied thinly might perform closer to an SPF 15 or 20 in practice.
A few labeling points worth knowing before you buy:
- “Broad Spectrum” is a regulated claim, not marketing language, and it requires passing a specific FDA test that checks UVA performance relative to SPF.
- Water-resistance claims specify a duration, either 40 or 80 minutes, after which reapplication is required.
- The FDA has discussed capping labeled SPF values given how little additional protection very high numbers provide once a product reaches broad-spectrum SPF 30 or higher performance.
The FDA’s OTC monograph for sunscreen drug products lays out these testing and labeling rules in detail, covering everything from how broad-spectrum status gets determined to what water-resistance claims require on the label.
What PA and PPD Measure, and Why UVA Protection Matters
PA stands for Protection Grade of UVA, a rating system that originated in Japan and is now common across Korean sun care. It is built on a test called PPD, or persistent pigment darkening, which measures how much a sunscreen delays visible skin darkening caused by UVA exposure compared to unprotected skin.
The PA scale breaks down into four tiers based on the PPD result: PA+ corresponds to a PPD of 2 to 4, PA++ to a PPD of 4 to 8, PA+++ to a PPD of 8 to 16, and PA++++ to a PPD of 16 or higher. Each added plus sign roughly doubles the UVA protection of the one before it, so the jump from PA++ to PA+++ is a meaningful upgrade, not a cosmetic difference.
UVA protection deserves this much attention because of what UVA rays actually do. UVA radiation penetrates deeper into the skin than UVB and contributes significantly to photoaging and pigmentation changes, and unlike UVB it passes through window glass and stays fairly constant throughout the day and across seasons. That makes UVA a daily concern rather than a beach-day concern, which is exactly why a rating that isolates UVA strength is useful.
A practical note on where you will see this label: PA markings show up almost exclusively on Japanese and Korean sunscreens. U.S. products sold under FDA rules use the “broad spectrum” designation instead, which confirms a product passed a UVA test relative to its SPF but does not break UVA protection into tiers the way PA does. If you shop both markets, the PA system gives you a more granular read on UVA strength than anything printed on a typical U.S. label.
Reading U.S. and Imported Labels Side by Side
Comparing a U.S. sunscreen to an imported Korean one means reading two different labeling systems that were not designed to match each other. Understanding what each one actually certifies keeps you from either overestimating or dismissing a product based on an unfamiliar mark.
A U.S. product’s “Broad Spectrum” claim means it passed a specific FDA test confirming its UVA protection keeps pace with its SPF, and broad-spectrum sunscreens rated SPF 15 or higher are allowed to claim they reduce the risk of skin cancer and early skin aging when used as directed alongside other sun protection measures. Products that have not passed that test can only claim to help prevent sunburn, a smaller claim with a smaller meaning.
Water-resistance labeling follows its own rule: a product can claim resistance for 40 or 80 minutes of swimming or sweating, and the label is required to say so directly rather than implying all-day water resistance.
Here is how to reconcile the two systems when you are holding an imported product with a PA rating on it:
- Use PA as a bonus UVA signal, not a replacement for checking broad-spectrum status.
- Confirm the SPF number still meets your baseline of 30 or higher.
- Don’t assume PA++++ automatically means broad spectrum under FDA definitions; the tests are different and were not built to translate directly.
- Treat a high PA and a broad-spectrum claim together as the strongest combined signal you can find on a label.
One resource that walks through this translation in more depth: our breakdown of what PA++++ actually means in UVAPF terms compares Korean PA labeling against U.S. broad-spectrum claims side by side.
Pro Tip: When a product shows both a PA rating and a broad-spectrum statement, you are looking at a sunscreen that has been tested under two independent UVA standards, which is about as much reassurance as a label can offer.
Which Rating to Prioritize and a Simple Rule for Choosing
The rule that covers most situations: choose a broad-spectrum sunscreen rated SPF 30 or higher, then check for strong UVA coverage through a PA+++ or PA++++ mark or a verified broad-spectrum claim. SPF and PA are not interchangeable, so neither one alone tells the full story, and a product that scores well on both gives you balanced coverage against sunburn and the deeper, cumulative damage UVA causes.
How that rule adjusts depending on your day:
- Everyday indoor and urban exposure. A broad-spectrum SPF 30 with at least PA+++ covers incidental sun through windows, commuting, and errands.
- Outdoor or all-day sun exposure. Step up to SPF 50 with PA++++ and a water-resistant formula, since sweat and sun intensity both work against thinner protection.
- Pigmentation concerns or post-procedure skin. Prioritize the highest available UVA rating since UVA is the primary driver of pigmentation, and pair it with consistent reapplication rather than relying on SPF alone.
Dermatologists consistently point out that fit and consistent use matter more than chasing marginal differences between SPF 30 and SPF 50. A sunscreen with a lighter, more wearable texture that you actually reapply beats a heavier, higher-rated one left in a drawer. Our guide to Korean sunscreen textures and finishes breaks down which formulas tend to fit daily wear versus heavier outdoor use.
Application Mistakes That Quietly Undo Your Protection
The gap between a sunscreen’s labeled protection and what you actually get usually comes down to how much you apply and how often. Lab testing is based on 2 mg/cm², which translates to a nickel-sized dollop for the face and neck and roughly one ounce, about a full shot glass, to cover the body. Most people apply far less, which drops an SPF 50 product’s real-world performance closer to SPF 15 or 20.
Common gaps and quick fixes:
- Ears, hairline, and back of the neck get skipped constantly; a sunscreen stick makes these spots faster to cover without mess.
- Lips are rarely protected at all; a tinted SPF lip product closes that gap.
- Reapplication after two hours gets forgotten during long outdoor stretches, especially after swimming or heavy sweating, which washes off even water-resistant formulas eventually.
- Thin application on the face happens when people treat sunscreen as a finishing step rather than a full layer; a tinted sunscreen or a dedicated sunscreen base under makeup helps you apply a visible, even coat.
Pro Tip: Keep a travel-size sunscreen stick in your bag for reapplication, and treat the morning application as a full step in your routine rather than an afterthought tacked onto moisturizer.
How We Think About UVA and UVB Protection When Curating Sunscreens
We evaluate sunscreens against the same checklist: broad-spectrum SPF 30 or higher, a clear UVA signal through a PA rating or a verified broad-spectrum claim, a texture suited to daily wear, and formulation choices that work across different skin types and concerns. Korean sunscreens frequently carry PA ratings, and we find that a visible PA+++ or PA++++ mark paired with SPF 50 gives shoppers one of the clearer combined signals available on a label. Our explainer on why Korean SPF formulas differ from U.S. ones covers how ingredient choices and texture goals shape these products, which matters as much as the numbers printed on the box.
— Lunara
Start With a Balanced SPF and PA Combination
Our sunscreen selection follows the same standard outlined in this guide: broad-spectrum SPF 30 or higher with a clear UVA signal, whether that shows up as PA+++, PA++++, or a verified broad-spectrum claim. One product available that carries both markings clearly is the Beauty of Joseon Relief Sun, rated SPF 50+ PA++++, a straightforward example of the combination this article recommends.
If you want a lighter daily option with added coverage, a tinted formula like Maison Dovellé’s BB Cream pairs cosmetic coverage with SPF, which can help with the lips-and-face gaps mentioned earlier. For browsing our full lineup of facial sunscreens and daily protective products, start with our face care collection and filter for your preferred texture and finish. This is a shopping resource, not medical advice, so pair it with guidance from a dermatologist for any specific skin concern.
This article is general information, not a substitute for advice from a qualified doctor. Consult a qualified healthcare professional about your own circumstances before acting on anything here.
FAQ
What is the difference between SPF and PA rating?
SPF measures protection against UVB rays, the ones responsible for sunburn, while PA measures protection against UVA rays, which contribute to aging and pigmentation. A sunscreen can carry strong numbers on one scale and weaker performance on the other, so checking both, or confirming broad-spectrum status, gives you the fuller picture.
What does PA++++ mean on a sunscreen label?
PA++++ means a sunscreen scored a PPD of 16 or higher in persistent pigment darkening testing, the strongest tier in the PA system. It signals strong UVA protection and is common on Korean and Japanese sunscreens, including options like the Beauty of Joseon Relief Sun.
Is SPF 30 enough, or should I choose SPF 50?
Dermatologists recommend broad-spectrum SPF 30 or higher as a reliable everyday baseline, since SPF 30 filters about 97% of UVB rays compared to about 98% for SPF 50. The bigger factor is applying enough product and reapplying every two hours, rather than which of the two numbers you pick.
Why don’t U.S. sunscreens show a PA rating?
U.S. sunscreens follow FDA rules, which use a “Broad Spectrum” claim rather than the tiered PA system to indicate UVA protection. The PA system originated in Japan and is widely used across Korean sun care, so you will mainly see it on imported products rather than domestic ones.
How often should I reapply sunscreen for it to work?
Reapply sunscreen every two hours, and immediately after swimming, sweating, or toweling off, regardless of the SPF or PA rating printed on the bottle. Even a water-resistant formula wears off within its tested window, 40 or 80 minutes, and needs to be reapplied to keep working.
Sources
- FDA OTC Monograph M020 — Sunscreen drug products for OTC human use
- Tufts Medicine — Dermatologists’ guide to sunscreen
