UV Index Guide & Sun Protection Calculator
Enter today's UV index and your skin type to see the recommended SPF, estimated time to burn, clothing advice, and a complete sun safety checklist. Based on WHO UV guidelines and the Fitzpatrick skin type scale. Calculated entirely in your browser.
Select UV Index & Skin Type
How UV Index Guide & Sun Protection Calculator Works
Check recommended SPF, time to burn, and clothing protection for any UV index. UV safety guide for all skin types. needed. Enter your values into the form above and the calculator processes them instantly in your browser — no data is sent to any server.
Understanding the UV Index Scale
The UV index (UVI) is a standardised scale developed by the World Health Organisation and World Meteorological Organisation to measure the intensity of ultraviolet radiation from the sun that reaches the Earth's surface. It runs from 0 (no UV) to 11+ (extreme UV). A UV index of 1-2 is considered low risk; 3-5 is moderate; 6-7 is high; 8-10 is very high; and 11+ is extreme. The index accounts for the sun's elevation angle, cloud cover, ozone layer thickness, altitude, and surface reflection (snow can reflect up to 80% of UV, sand about 15%). Based on WHO UVI guidelines (2002) and updated WHO solar UV index guidelines (2022), sunscreen application is recommended whenever the UV index reaches 3 or above.
UV radiation consists of UVA (315-400nm) and UVB (280-315nm). UVB causes sunburn and is the primary driver of vitamin D synthesis and skin cancer risk. UVA penetrates deeper into skin, contributing to premature ageing and also to skin cancer risk. Standard SPF ratings measure protection against UVB only; broad-spectrum sunscreens also protect against UVA.
Fitzpatrick Skin Types and Sun Sensitivity
The Fitzpatrick scale, developed by Thomas Fitzpatrick MD at Harvard Medical School, classifies human skin into six types based on its response to UV radiation. Type I (very pale, red or blonde hair, blue eyes, freckles) always burns and never tans. Type II (fair skin) usually burns and tans minimally. Type III (medium skin, light brown hair) sometimes burns and tans gradually. Type IV (olive skin, dark hair) rarely burns and tans easily. Type V (brown skin) very rarely burns. Type VI (dark brown to black skin) almost never burns but is not immune to UV damage or skin cancer — melanoma can occur in all skin types, including darker ones.
Estimated time to sunburn (MED — minimal erythema dose) without sunscreen at UV index 8: approximately 10-15 minutes for Type I-II, 25-40 minutes for Type III-IV, and 60-90 minutes for Type V-VI. SPF 30 multiplies these times by approximately 30 (e.g., Type I at UV index 8 with SPF 30 could stay out 300-450 minutes before the theoretical burn threshold, though reapplication every 2 hours is still required as sunscreen degrades).
How to Apply Sunscreen Correctly
Apply sunscreen 15-30 minutes before sun exposure to allow it to bind to the skin. Use approximately 2 mg/cm² — about a teaspoon for the face and neck, and a shot glass for the full body. Reapply every 2 hours or immediately after swimming, sweating heavily, or towel drying, regardless of whether the original application claimed water resistance. For daily use (commuting, indoor exposure through windows), a broad-spectrum SPF 30+ applied to the face, neck, and hands is sufficient. For outdoor activities at high UV index, SPF 50+ with broad-spectrum UVA/UVB protection is the standard recommendation. Last updated: March 2026.
Frequently Asked Questions
What UV index is dangerous?
A UV index of 6 or above is considered high risk and requires active sun protection for all skin types. UV index 8-10 is very high — unprotected skin can burn in as little as 10-15 minutes for fair skin. UV index 11+ is extreme and can cause burns within 10 minutes even for medium skin tones. The WHO recommends wearing SPF 30+ sunscreen, protective clothing, and seeking shade whenever the UV index is 3 or above.
What SPF should I wear for different UV index levels?
UV index 1-2 (low): SPF 15 sufficient for most skin types. UV index 3-5 (moderate): SPF 30 recommended. UV index 6-7 (high): SPF 30-50 required, reapply every 2 hours. UV index 8-10 (very high): SPF 50+ essential, stay in shade during peak hours. UV index 11+ (extreme): maximum protection required — SPF 50+, hat, UPF clothing, avoid midday sun entirely.
What time of day is UV index highest?
UV radiation is strongest between 10am and 2pm (or 11am-3pm in daylight saving time), when the sun is highest in the sky. This is when UV index reaches its daily peak. The UV index is typically 20-25% lower one hour before or after the peak. Cloud cover can reduce UV index by 25-50%, but a significant amount of UV still penetrates through clouds.
How does the UV index affect different skin types?
The Fitzpatrick scale classifies skin types I to VI. Type I (very fair, always burns) can burn in as little as 10 minutes at UV index 8. Type III-IV (medium/olive skin) may take 30-45 minutes to burn at the same UV index. Type V-VI (dark/very dark skin) has more natural UV protection but still risks long-term damage. No skin type is immune to UV damage — SPF is recommended for everyone.
Does UV index affect vitamin D production?
Yes — vitamin D synthesis requires UVB radiation and typically takes 5-30 minutes of midday sun exposure on arms and legs. At low UV index (1-2), you may need longer sun exposure for adequate vitamin D. At very high UV index (8+), you can synthesise sufficient vitamin D within 5-10 minutes, but continuing to stay in the sun increases skin damage risk without adding vitamin D benefit.