When choosing sunscreen, it’s easy to assume that SPF 50 must offer twice as much protection as SPF 30. After all, 50 is almost double 30. But sunscreen ratings don’t work that way.
SPF 50 provides more protection than SPF 30, but it isn’t twice as effective. The difference is smaller than many people realise.
SPF stands for Sun Protection Factor. It measures how effectively a sunscreen protects the skin from UVB radiation - the type of ultraviolet radiation primarily responsible for sunburn. When you purchase Sunscreen, also check it covers UVA – the type of ultraviolet radiation that damages and ages your skin, not all do.
In Australia, sunscreens intended primarily to protect against UV radiation are also regulated by the Therapeutic Goods Administration (TGA). Therapeutic Goods Administration (TGA)
The SPF number is based on the amount of UVB radiation that reaches the skin when sunscreen is applied correctly under laboratory conditions.
So, while SPF 50 provides a higher level of protection, the difference is around one percentage point—not double the protection. Therapeutic Goods Administration (TGA)
The remaining UVB exposure may sound small, but even a modest increase in protection can be helpful - particularly considering most people also apply less sunscreen than is needed to achieve the protection shown on the label. Applying too little sunscreen can significantly reduce the level of protection you receive.
No. A higher SPF does not mean you can stay in the sun for twice as long or wait longer before reapplying.
Both SPF 30 and SPF 50 need to be applied generously and reapplied according to the product instructions. Sunscreen can wear off through sweating, swimming, toweling off and general movement, regardless of its SPF rating.
For the best results, apply sunscreen generously to clean, dry skin before heading outdoors. Reapply regularly, particularly after swimming, sweating or toweling off.
SPF mainly tells you about protection from UVB radiation. It does not provide the full picture of protection against UVA radiation, which can contribute to premature skin ageing, long-term skin damage and skin cancer.
For everyday use, choose a sunscreen labelled ‘broad spectrum’. This means it provides protection against both UVA and UVB radiation.
In Australia, sunscreen labels should also include an AUST number, confirming that the product is included in the Australian Register of Therapeutic Goods. Therapeutic Goods Administration (TGA)
Yes. SPF 30 provides a high level of protection when it is applied correctly and reapplied as directed. SPF 50 offers very high protection, but neither sunscreen blocks every UV ray.
The most important sunscreen is one you will use properly and consistently. If you prefer the feel, finish or price of an SPF 30 product, using it generously every day is likely to provide better protection than applying a small amount of SPF 50.
Sunscreen is also only one part of a complete sun-protection routine. When UV levels are high, combine sunscreen with protective clothing, a broad-brimmed hat, sunglasses, shade and avoiding direct sun where possible.
SPF 50 is not twice as good as SPF 30. SPF 50 filters around 98% of UVB radiation, compared with around 97% for SPF 30.
That difference can still be worthwhile, which is why SPF 50 is generally recommended where available. But applying enough sunscreen, reapplying it regularly and using other forms of sun protection are just as important as the number on the bottle.
No matter which sunscreen you choose, using it consistently helps reduce your exposure to UV radiation and supports healthier skin over time.
