UV Index and Skin Types
Not all skin reacts to the sun in the same way. To help you protect yourself effectively, Sun Day uses the Fitzpatrick Scale, a scientific classification that describes how different skin types respond to ultraviolet (UV) radiation.
The Fitzpatrick Scale
| Type I | Always burns, never tans (very fair skin). |
| Type II | Usually burns, tans minimally (fair skin). |
| Type III | Sometimes mild burn, tans uniformly (medium skin). |
| Type IV | Burns minimally, always tans well (olive skin). |
| Type V | Very rarely burns, tans very easily (dark brown skin). |
| Type VI | Never burns, deeply pigmented (black skin). |
How the UV Index Changes the Rules
A UV index of 3 might be safe for Type IV skin for 45 minutes, while Type I skin could burn in less than 15. Sun Day calculates your "Time to Burn" and "Vitamin D Synthesis" specifically for your type.
Protect Your Skin
Download Sun Day and get personalized alerts for your skin type.
Frequently asked questions
What is the Fitzpatrick scale?
A scientific classification of six skin phototypes describing how skin responds to UV: from Type I (always burns, never tans) to Type VI (never burns, deeply pigmented). It is the standard reference in dermatology and the basis of Sun Day's calculations.
At what UV index does skin burn?
It depends on your phototype. At UV index 3, Type IV skin can typically stay out about 45 minutes, while Type I skin can burn in under 15. Sun Day computes a personal time-to-burn from the live UV index and your skin type.
Do dark skin tones need sun protection too?
Yes. Types V and VI rarely burn, but UV-induced damage and photoaging still accumulate, and hyperpigmentation is common. Protection recommendations simply differ by phototype.
How can I know my safe sun exposure time?
Sun Day is free and calculates it for you: it combines the real-time UV index at your location with your Fitzpatrick type to display remaining safe exposure and vitamin D synthesis. It is a prevention aid, not a medical device.