What is SPF?

Sun Protection Factor (SPF) measures a sunscreen’s protection against sunburn or sun damage from ultraviolet rays.

A sunscreen with a higher SPF means it takes more UV radiation to get sunburn after applying it. The higher the SPF, the better the protection.

SPF does not tell you how long you spend in the sun. Instead, it allows you to compare different sunscreens.

How is SPF tested?

A sunscreen’s SPF is found by testing it on 10 volunteers with varying skin types. The sunscreen is applied to an area of the volunteers’ skin, while a similar-sized area is left alone for comparison.

A UV lamp is shone on both areas, and a technician finds the smallest amount of UV light needed to cause redness in both. After comparing the results of the 10 volunteers, the SPF value can be found.

How is broad-spectrum sunscreen tested?

To test broad-spectrum protection, a thin layer of sunscreen is put on a plate and exposed to UVA rays.

A spectrophotometer determines whether UVA rays that would penetrate deeper into the skin are protected against. When this protection is at least a third of the sunscreen’s SPF level, it is labelled as broad-spectrum. 

What is the difference between SPF30 and SPF50 sunscreen?

SPF30 filters 96.7% of UV radiation. SPF50 filters 98% of UV radiation. Both provide excellent protection when applied properly. 

How can we be sure that the sunscreen is made to a certain standard?

Cancer Society sunscreen uses the latest science in its formulation which has been developed by scientists with the goal of protecting kiwis from our harsh UV radiation to reduce the incidence of skin cancer.


All batches of Cancer Society sunscreen are manufactured under these strict regulations which meet the same standards as to which prescription medicine is produced in Australia. They are thoroughly tested to meet the claims stated on the products.


The Cancer Society of New Zealand voluntarily adheres to the AS/NZS 2604:2012 Sunscreen Standard under which the manufacture of sunscreens is strictly regulated. Cancer Society Sunscreens are on track to comply with the new testing requirements to meet the new 2021 Sunscreen Standard,  AS/NZS 2604:2021. This is required by all sunscreen manufacturers by the 31st December 2027.


SPF test results are available upon request by emailing mail@sunscreen.org.nz

Last updated: October 2, 2023