Fitzpatrick Skin Type & UV Index Guide
The same scale and formula the app uses to build your routine — not a simplified version.
What Is the Fitzpatrick Scale?
The Fitzpatrick scale is a six-category system developed by dermatologist Thomas Fitzpatrick in 1975 to classify skin color and how it responds to UV exposure — from Type I (very fair, always burns) to Type VI (dark, never burns). It's still the standard reference dermatologists use today for sun-sensitivity and phototherapy dosing.
How "Safe Time" Is Calculated
Baseline burn time is the number of minutes of unprotected exposure before burning risk rises, measured at UV Index 1. As UV Index rises, safe time drops roughly proportionally — the app applies an approximate Minimal Erythemal Dose (MED) rule: safe minutes ≈ baseline minutes ÷ today's UV Index. A Type III baseline of 200 minutes at UV 1 becomes roughly 25 minutes at UV 8, which is why the same skin type needs a completely different routine on a high-UV day versus a mild one.
What the Number Actually Means
The standard WHO/EPA scale used worldwide for UV forecasts.
Low
Minimal risk for most people. Sunburn is unlikely in under an hour of exposure without protection.
Moderate
Some risk. Seek shade during midday hours and wear SPF if outside for an extended time.
High
Protection required. Sunburn risk is significant — SPF, a hat, and shade during peak hours all matter.
Very High
Extra precautions needed. Unprotected skin can burn in well under 30 minutes for fair skin types.
Extreme
Avoid sun exposure during midday hours entirely if possible. Unprotected skin can burn in minutes.
A Note on Safety
This guide and the app's routines are educational tools, not medical advice. The Fitzpatrick estimate, UV display, and tanning routine are informational only. Always wear broad-spectrum SPF, seek shade during peak UV hours, and consult a qualified dermatologist if you have fair skin, a personal or family history of skin cancer, photosensitivity, unusual moles, or are pregnant or taking photosensitizing medication.