What SPF should I use for my skin type?

The American Academy of Dermatology recommends a minimum SPF 30 for most people. Skin Types I–II or extended outdoor activity warrant SPF 50+. Reapply every 2 hours and after swimming or sweating.

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Sun Exposure Calculator

UV index risk, safe exposure time by skin type, required SPF, and vitamin D synthesis — based on WHO guidelines and published dermatology research.

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Educational Use Only — Not Medical Advice

Results are estimates based on generalised models (WHO UV guidelines, Fitzpatrick scale). Actual safe exposure depends on cloud cover, altitude, reflective surfaces, medication, and individual variation. Consult a dermatologist for personal guidance. People with skin conditions, history of skin cancer, or photosensitivity should seek medical advice before sun exposure.

UV Index (0–13+)

Check your local weather app or EPA UV Index scale.

Planned Duration (minutes)

Fitzpatrick Skin Type

Fair skin; light eyes; light hair

SPF Sunscreen (0 = none)

Body Area Exposed

WHO UV Index Scale

Low (0–2)Wear sunglasses on bright days. If you burn easily, cover up and apply SPF 15+.

Moderate (3–5)Take precautions — cover up, wear SPF 15–30, and seek shade near solar noon.

High (6–7)Protection required. Wear SPF 30+, wide-brim hat, and UV-blocking sunglasses. Seek shade midday.

Very High (8–10)Extra protection needed. Minimise outdoor activity 10 AM – 4 PM. SPF 50+ essential.

Extreme (11+)Stay indoors. Full protection at all times.

Frequently Asked Questions

What is the UV Index and where can I find it?▼

The UV Index (UVI) is a standardised measure of ultraviolet radiation at the Earth's surface, developed jointly by the WHO, UNEP, and WMO. It ranges from 0 (no UV) to 11+ (Extreme). Check your local weather app, the EPA UV Index forecast (USA), or the WHO Global UV Index report for your region.

What is the Fitzpatrick skin type scale?▼

The Fitzpatrick scale (1975) classifies human skin into six phototypes based on melanin content and response to UV radiation. Type I (very fair) has the lowest melanin and burns fastest; Type VI (dark) has the most melanin and the highest natural protection. The scale is used widely in dermatology to assess sunburn risk and UV sensitivity.

What SPF sunscreen should I use for my skin type?▼

The American Academy of Dermatology recommends a minimum of SPF 30 for most people, applied 15 minutes before going outside and reapplied every 2 hours. For Skin Types I–II or extended outdoor activity, SPF 50+ is advised. Note that SPF 30 blocks about 97% of UVB and SPF 50 blocks about 98% — the difference is small but matters for very sensitive skin.

How does sun exposure produce vitamin D?▼

UVB radiation (290–315 nm) converts 7-dehydrocholesterol in the skin to pre-vitamin D₃, which is further converted to vitamin D₃ (cholecalciferol) by body heat. Vitamin D₃ is then processed in the liver and kidneys to its active hormonal form. Sunscreen effectively blocks UVB, reducing vitamin D synthesis. People at higher latitudes, with darker skin, or who work indoors are at higher risk of deficiency (Holick MF, NEJM 2007).

Can I get vitamin D through a window?▼

Standard glass blocks nearly all UVB (290–315 nm) while transmitting UVA. Since UVB drives vitamin D synthesis, sitting by a closed glass window provides minimal vitamin D production. Specialised UV-transmitting glass exists but is rare in ordinary buildings.

Does cloud cover reduce UV exposure?▼

Clouds reduce UV radiation but not by as much as people assume. Thin to moderate cloud cover can still allow 50–80% of UV to pass through, while heavy overcast may reduce UV to 25–30% of clear-sky levels. Snow, sand, and water can also increase UV exposure by reflecting radiation — snow reflects up to 80% of UV.

Scientific References

World Health Organization. Global Solar UV Index: A Practical Guide. WHO/SDE/OEH/02.2. Geneva: WHO; 2002.
Holick MF. “Vitamin D deficiency.” New England Journal of Medicine 2007;357(3):266–281.
Webb AR, Kline L, Holick MF. “Influence of season and latitude on the cutaneous synthesis of vitamin D₃.” J Clin Endocrinol Metab 1988;67(2):373–378.
Schalka S, Steiner D, et al. “SPF: An important distinction between in vitro and in vivo.” Journal of Cosmetic Dermatology 2012;11(1):1–7.
Fitzpatrick TB. “The validity and practicality of sun-reactive skin types I through VI.” Archives of Dermatology 1988;124(6):869–871.
ICNIRP. “Guidelines on limits of exposure to ultraviolet radiation of wavelengths between 180 nm and 400 nm.” Health Physics 2004;87(2):171–186.

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WHO UV Index Scale

Low (0–2)Wear sunglasses on bright days. If you burn easily, cover up and apply SPF 15+.

Moderate (3–5)Take precautions — cover up, wear SPF 15–30, and seek shade near solar noon.

High (6–7)Protection required. Wear SPF 30+, wide-brim hat, and UV-blocking sunglasses. Seek shade midday.

Very High (8–10)Extra protection needed. Minimise outdoor activity 10 AM – 4 PM. SPF 50+ essential.

Extreme (11+)Stay indoors. Full protection at all times.

Frequently Asked Questions

What is the UV Index and where can I find it?▼

What is the Fitzpatrick skin type scale?▼

What SPF sunscreen should I use for my skin type?▼

How does sun exposure produce vitamin D?▼

Can I get vitamin D through a window?▼

Does cloud cover reduce UV exposure?▼

Scientific References

World Health Organization. Global Solar UV Index: A Practical Guide. WHO/SDE/OEH/02.2. Geneva: WHO; 2002.

Holick MF. “Vitamin D deficiency.” New England Journal of Medicine 2007;357(3):266–281.

Webb AR, Kline L, Holick MF. “Influence of season and latitude on the cutaneous synthesis of vitamin D₃.” J Clin Endocrinol Metab 1988;67(2):373–378.

Schalka S, Steiner D, et al. “SPF: An important distinction between in vitro and in vivo.” Journal of Cosmetic Dermatology 2012;11(1):1–7.

Fitzpatrick TB. “The validity and practicality of sun-reactive skin types I through VI.” Archives of Dermatology 1988;124(6):869–871.

ICNIRP. “Guidelines on limits of exposure to ultraviolet radiation of wavelengths between 180 nm and 400 nm.” Health Physics 2004;87(2):171–186.