Following a survey, a study published in 2015 in JAMA Dermatology reveals that fewer than half of participants can correctly read a sunscreen label and only 43% understand what the SPF rating means. This finding highlights a lack of information that can confuse consumers faced with a range of sun care products. Many end up choosing at random without noting essential details. So what does SPF indicate? In this article, we explain the meaning of this key term.
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Sun protection: what is SPF and what does it mean?
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Published June 23, 2021,
updated on June 23, 2025,
by
Stéphanie, PhD, Doctorate in Life and Health Sciences
—
11 min read
Sunscreen labelling: what do the SPF abbreviation and the following number indicate?
The primary UV filters are products that protect against UV radiation (e.g. beach sunscreens), whereas for secondary UV filters this function does not apply (e.g. tinted skincare products, lipsticks, etc.).
Introduced in the 1960s by Franz GREITER, the SPF index—short for “Sun Protection Factor”—is an indicator of a sunscreen’s ability to block erythemal UV rays that cause sunburn. It is expressed on a scale from 2 to 50+, indicating maximum protection. Labelling rules may vary by country. To address consumer confusion over efficacy and duration of protection, several countries have set specific labelling requirements.
Is there a difference between the acronyms IP, SPF and FPS? These three terms denote the same concept: the level of protection provided by a sunscreen against UV rays responsible for actinic erythema. The acronym FPS stands for "Facteur de Protection Solaire" in French, while SPF is its English equivalent (Sunburn Protection Factor). The abbreviation IP, for "Indice de Protection", is used in some French-speaking countries. Whatever the brand or country of purchase, it is a universal value.
| Country | Authorised SPF value |
|---|---|
| European Union (in accordance with Cosmetics Regulation (EC) No. 1223/2009) | Minimum SPF of six; SPF values above 50 must be indicated as SPF 50+ |
| United States (in accordance with the FDA final rule, 2011) | Minimum SPF of 2; broad-spectrum sunscreen products with SPF values from 2 to 14 must be labelled with the warning "Skin cancer/skin ageing alert"; SPF 60+ is the maximum SPF indicated on the label |
| Australia / New Zealand (in accordance with AS/NZS 2604:2021) | Minimum SPF 4; maximum permitted value shown as SPF 50+ on products with SPF ≥ 60 only; prevention claims (cancers, keratoses, sunspots) may be displayed for broad-spectrum sunscreens with SPF ≥ 30; minimum SPF 15 for secondary sunscreens |
| Canada (according to Health Canada, Monograph Reference Document on Sunscreens, 2012) | Minimum SPF of 2; SPFs over 50 must be indicated as SPF 50+; sunscreens lacking broad-spectrum protection or with SPF below 15 must bear the warning "Skin cancer/skin ageing alert" |
| Japan (according to the JCIA) | Minimum SPF 2; SPF values above 50 must be indicated as SPF 50+; claims such as “prevents wrinkles” are prohibited. |
| China (according to the CFDA) | Minimum SPF of 2; SPF values above 50 must be indicated as SPF 50+ |
Sunscreen labelling directives by country.
Source: G. Pirotta. Sunscreen regulation worldwide. In The Handbook of Environmental Chemistry. Springer International Publishing (2020).
Although useful, this measure remains imperfect. It reflects a sunscreen’s capacity to block certain UV rays that cause sunburn. It refers to the amount of solar energy required to produce slight reddening on protected skin, in accordance with ideal sunscreen application conditions, compared with the energy required for fully unprotected skin. It does not account for the effects of the remaining UV rays, which can contribute to premature skin ageing (photoageing) and to the development of skin cancers (photocarcinogenesis).
It is often stated that UVB rays cause sunburn. However, erythemal UV radiation consists of 85% UVB (between 290 and 320 nm) and 15% UVA-UVA-II (between 315 and 340 nm).
Contrary to common belief, SPF does not indicate how long one can stay in the sun without risk. Many people think that if someone begins to redden after ten minutes outdoors without sunscreen, applying SPF 50 may allow them to stay in the sun 50 times as long before burning. That means they could stay in the sun for eight hours without sunburn (10 minutes × 50 = 500 minutes), about twice as long as with SPF 30.
However, this is a misconception. SPF relates to a dose of solar energy received and filtered, not to a fixed duration. Several factors can affect sunscreen protection: UV intensity at a given time and place, skin phototype, amount of sunscreen applied, activities such as swimming, use of certain medications, and reapplication frequency. Even a product with high SPF requires ample application and reapplication at regular intervals to maintain optimal protection.
In addition to a clear SPF label, sunscreens must also indicate a description of the level of protection they offer (low, medium, high or very high) on the same label.
| Protection level | Measured SPF | SPF stated on the label |
|---|---|---|
| Low protection | 4 – 14.9 | |
| Moderate protection | ` tags, and preserve `15 - 29,9 | 15, 20, 25 |
| High protection | 30, 50 | |
| Very high protection | ⩾ 60 |
Sunscreen categories based on SPF.
Source: Australian Government – Department of Health and Aged Care. Australian regulatory guidelines for sunscreens (2023).
What does the number displayed after SPF indicate?
The number following the SPF label indicates the percentage of erythemal UV rays that are blockedThe higher the SPF, the greater the percentage of UV light it blocks. SPF 50 means that 1/50 of erythemal UV rays reach the skin, assuming correct application. It provides 50 times more protection than no sunscreen. However, many people believe that a high SPF offers two or even three times the protection of SPF 30, creating a false sense of security.
In reality, the increase in protection is not linear. SPF 30 provides near-optimal protection when applied correctly, blocking about 97 per cent of erythemally effective UV rays. SPF 50, by comparison, blocks about 98 per cent and SPF 100 about 99 per cent. The difference in protection between SPF 30 and SPF 50 is minimal (around 1 per cent) and does not offer substantive additional protection. However, although protection gains are marginal, they may become significant for sensitive skin, fair phototypes or in contexts of frequent or prolonged exposure.
SPF alone does not guarantee protection. Assess the product formulation, including the “broad spectrum” label that covers long UVA. Apply and reapply at recommended intervals to maintain effective sun protection.
| SPF value | Percentage of UV radiation blocked by sunscreen | Amount of UV radiation not blocked by sunscreen |
|---|---|---|
| SPF 2 | 50% | 50% |
| SPF 15 | ||
| SPF 20 | ` tags (including `5% | |
| SPF 30 | ||
| FPS 50 | ` tags and keeping `98% | |
| SPF 80 | 98,75% | |
| SPF 100 | tags—including `99% | ` tags and keep `1% |
Amount of erythemal UV radiation blocked or transmitted by the sunscreen at different SPFs.
Source: SILVA DOS REIS V M et al. Sun protection factor: meaning and controversies. Anais Brasileiros de Dermatologia (2011)
Keep in mind that no sunscreen can block 100% of erythema-causing UV rays or prevent sunburn and resulting skin damage.
How is the SPF rating of a sunscreen determined?
To determine the SPF of a sunscreen, rigorous tests in vivo in laboratory (ISO 24444) are carried out on a non-tanned area of volunteers’ skin (e.g. the inner arm). The sunscreen is applied at 2 mg/cm2 of skin, before exposure to an artificial UV source (solar simulator) for about 20 minutes.
In Europe, SPF is accepted if measured on at least 10 participants.
After 24 to 48 hours, exposed skin areas are examined and the fraction of UV radiation required to cause slight redness with and without sunscreen is measured. The SPF value is the ratio of UV doses needed to induce a mild sunburn on protected versus unprotected skin.
Although this is the current SPF test, several test methods in vitro are set to be adopted: the in vitro double-plate method (ISO 23675) and the hybrid diffuse reflectance spectroscopy method (HDRS–ISO 23698) are in the final stage of international standardisation. They should become the first ISO standards published for in vitro SPF testing in vitro.
Although laboratory testing determines a sunscreen’s SPF, it indicates efficacy against erythemal rays, not the UVA, which penetrate deeper.
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Key facts about SPF.
The sun protection factor (SPF) can be considered as the "protection factor against sunburn".
The value following the SPF label indicates the amount of erythemogenic UV rays filtered by a sunscreen.
The higher the SPF, the more the additional benefits decrease.
It is recommended to apply a sunscreen daily with an SPF of at least 30 to all exposed areas of skin.
No sunscreen can filter 100% of UV rays responsible for sunburn.
Sources
DOWDY J. C. & al. Simplified method to substantiate SPF labeling for sunscreen products. Photodermatology, Photoimmunology and Photomedecine (2003).
SILVA DOS REIS V M. & al. Sun protection factor: meaning and controversies. Anais Brasileiros de Dermatologia (2011).
BILODEAU D. & al. Beyond UV radiation: A skin under challenge. International Journal of Cosmetic Science (2013).
OSLIN D. W. & al. Minimal erythema dose (MED) testing. Journal of Visualized Experiments (2013).
KUNDU R. V. & al. Assessment of consumer knowledge of new sunscreen labels. JAMA Dermatology (2015).
LIM H. W. & al. Sunscreens: An update. American Journal of Clinical Dermatology (2017).
RIGEL D. S. & al. SPF 100+ sunscreen is more protective against sunburn than SPF 50+ in actual use: Results of a randomized, double-blind, split-face, natural sunlight exposure clinical trial. Journal of American Academy of Dermatology (2018).
PIROTTA G. Sunscreen regulation in the world. The Handbook of Environmental Chemistry. Springer International Publishing (2020).
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