2026-11-07 · 7 min read

SPF 30 to 55 and PA++++: how a sun protection number gets onto a label

An SPF number on a carton is not a marketing claim. It is the output of a human test, and the label value is deliberately set below the measured one. Here is the arithmetic behind that gap.

The short answer: SPF is measured on human volunteers, and the number printed on the pack must not exceed what the test measured. A factory quoting "SPF 30 to 55" is describing a formulation range it can support with test data, not a dial it turns.

How SPF is actually measured

The recognised method uses human volunteers. A defined dose of product is applied to a marked area of skin, the area is exposed to a solar simulator, and the minimal dose that produces redness is compared against unprotected skin. The ratio is the SPF.

Two consequences follow from this:

The number has a confidence interval. It comes from a panel, so it carries statistical uncertainty. This is why the label value is set below the measured mean rather than at it.
In-vitro results cannot support a label claim. A spectrophotometer reading on a plate is a development tool. Regulators in the Gulf, the EU and the US require human data.

Why the label number is lower than the test number

If a formula measures SPF 58, the label will typically say 50. That gap is not conservatism for its own sake — it accounts for:

Panel variability between test rounds
The difference between 2 mg/cm² applied in a lab and what a consumer actually applies, which is usually less
Degradation of the filter system over shelf life

A supplier who offers to print exactly the measured number is offering you a claim that will not survive a challenge test in your market.

UVA is a separate measurement

SPF describes UVB only. UVA protection needs its own evidence, and PA++++ is not a marketing grade — it corresponds to a defined level of UVA protection factor measured under a recognised method.

Two things to check on any sun-care report:

UVA-PF — the measured protection factor in the UVA range, which sets the PA rating
Critical wavelength — at or above the broad-spectrum threshold, the product qualifies as broad spectrum

A report showing SPF 50+ with no UVA line is half a report. In Gulf markets, where UVA exposure is high year-round, it is the half that matters.

Why the range is 30 to 55, not a single number

Different formulas support different measured values, and the label must sit below the measurement. A formulation that measures in the high 30s supports an SPF 30 label comfortably. One that measures in the low 60s supports SPF 50+.

The range also reflects cost. Higher SPF means more UV filter, and UV filters are among the most expensive ingredients in the formula. Moving from SPF 30 to SPF 50 is not a linear cost increase, because the filter load starts to affect texture, stability and cost per unit simultaneously.

The three things that quietly break an SPF claim

Filter recrystallisation in heat. An organic filter that comes out of solution at 60°C stops protecting, even though the label still says SPF 50. This is why stability testing at the hot end matters for sun care specifically.
Application rate assumptions. A formula tested at 2 mg/cm² and used at 1 mg/cm² delivers roughly the square root of the labelled protection, not the labelled protection.
Formula drift between the tested batch and the production batch. The report covers a specific formula code. If production substitutes a filter grade or adjusts a percentage, the report no longer describes the product in the carton.

What to demand before you print a carton

The in-vivo SPF report, naming the method and the testing laboratory
UVA-PF and critical wavelength on the same report
The formula code on the report matching the formula code in production
Stability data at the hot end, showing the filter system holds

FAQ

Can you make SPF 55?
We formulate across the SPF 30-55 range and PA++++, and the label value is set from the measured result. What we will not do is print a number the test did not support.

How long does SPF testing take?
It runs in parallel with stability work, and the report is issued after the panel completes. It is not a bottleneck if it is scheduled at the start rather than the end.

Is PA++++ the same as broad spectrum?
No. PA grades the UVA protection factor. Broad spectrum is a separate critical-wavelength criterion. A product can be PA++++ and still miss a market’s broad-spectrum labelling requirement.

Do I need my own SPF test for my market?
Usually yes, under your own entity and your market’s rules. Our report is supporting evidence; the filing is yours.