SPF and PA Testing for Sunscreens
Anyone can print SPF 50 on a pack. A brand that does it responsibly has a report behind the number. Here is how SPF and PA testing works, what to ask a laboratory and how to read the result.
What an SPF test measures
SPF compares how much UV it takes to redden skin with and without sunscreen. A testing laboratory applies the product to volunteers’ skin, exposes small test sites to a controlled dose of UV and compares the skin response with the same person’s unprotected skin. The result is a number, the sun protection factor.
Because the test uses people, it is done under ethical approval and with trained staff. A basic part of the method is a fixed amount of product: sunscreen testing commonly uses 2 milligrams per square centimetre of skin. Most people apply far less in real life, which is one reason a label should tell users to apply generously and reapply.
ISO methods and the Indian standard
| What is measured | Common method | Notes |
|---|---|---|
| SPF (UVB), on people | ISO 24444 | The international in vivo method; BIS lists IS 17494:2021 as the Indian equivalent |
| UVA protection, in a lab dish | ISO 24443 | In vitro method; the UVA result supports a broad-spectrum or PA claim |
| UVA protection, on people | ISO 24442 | In vivo alternative for UVA |
| Water resistance | Variation of the SPF test with water immersion | Separate test; a water-resistant claim needs its own result |
When we checked, the BIS listing for IS 17494:2021 showed the standard as withdrawn, with no replacement shown, so we do not claim a current Indian standard for in vivo SPF. Ask your laboratory which method it uses and have it written on the report. The ingredient side, including which UV filters are allowed, is covered in our BIS standards guide.
UVA protection and the plus signs
SPF only speaks for UVB, the rays that cause sunburn. UVA penetrates deeper, drives ageing and contributes to tanning and pigmentation. PA is a grading from PA+ to PA++++ based on a measured UVA protection factor: the more plus signs, the higher the UVA protection. A product claiming PA++++ should have a UVA result that supports it.
How to run a test for your product
Finalise the formula
Do not test a formula you still plan to change. A change in filters, emulsifier or fragrance can change the result.
Pick an accredited laboratory
Ask about accreditation, the method it follows and its volunteer ethics approval.
Send a retained batch
Send a sample from a real production batch, with the batch number noted.
Agree the claim
Tell the lab the SPF and PA you hope to claim; the test measures what the product actually achieves.
Receive the report
Check it carries the product name, batch, method, date and the lab’s details.
Print only what the report supports
Round down if the report is between claims. Keep the report on file.
Ask the laboratory how long the work takes and what it costs. We do not quote either because they depend on the lab and the claim.
What to look for
| Item on the report | Why it matters |
|---|---|
| Product and batch | Shows what was tested |
| Method and standard | Shows the test is recognised |
| Number of subjects and result per subject | Shows the SPF is a result of a proper panel, not a single person |
| Final SPF value | The number you may print, not a number you hope for |
| UVA result and PA grade | Supports the PA claim |
| Water resistance, if claimed | Separate result |
| Date and laboratory details | Needed if a marketplace or regulator asks |
Our sunscreen pages explain the formula side: sunscreen manufacturer, sunscreen gel, sunscreen spray, sunscreen stick and kids’ sunscreen.
When a new test is needed
Keep results with your batch records, and see stability testing for what happens to the product over time. Claims language is in cosmetic claims in India.
SPF and PA Testing for Sunscreens: common questions
Do I need to test SPF before printing it?
Yes. An SPF or PA claim should be backed by a test report on the final formula.
Does Formuluxe test SPF?
The test is done by an independent accredited laboratory. We help you prepare the sample and understand the report.
How much product is used in the test?
Sunscreen tests commonly use 2 milligrams per square centimetre, which is more than most people apply.
What is the difference between SPF and PA?
SPF covers UVB. PA grades UVA protection from PA+ to PA++++.
Do I need to retest after a small change?
Often yes. Ask the laboratory whether the change could affect the result.
Is SPF 100 better than SPF 50?
The extra protection is small, and a claim of that size needs a strong test. Honest wording matters more.
Planning a sunscreen?
Tell us the SPF you want and we plan the formula and testing.