Estimate UV radiation intensity from latitude, date, time, altitude, and cloud cover. Get sunburn time warnings and SPF recommendations. Pure frontend, no server uploads.
🌍 Input Parameters
📊 Results
• Wear UV400 sunglasses
• Wear long-sleeve sun protection clothing and wide-brim hat
• Stay in shade, avoid noon sun exposure
📖 What Can This UV Index Calculator Do?
The UV Index Calculator estimates solar ultraviolet radiation intensity based on latitude, date, time, altitude, cloud cover, and surface albedo. It provides UV index rating, sunburn time warning, and personalized sun protection recommendations. Ideal for outdoor activity planning, travel sun protection, and health management.
Key Features
- UV Index Estimation: Based on solar zenith angle and atmospheric attenuation model
- Sunburn Time Warning: Estimates time for unprotected skin to start reddening
- SPF Recommendation: Recommends appropriate sunscreen SPF based on UV index
- Risk Level Assessment: 0-11+ graded UV risk assessment
- Personalized Protection Advice: Specific protection measures based on risk level
How to Use
- Enter latitude: Input your location's latitude (positive for North, negative for South).
- Enter altitude: Input altitude in meters (higher altitude = stronger UV).
- Select date and time: Choose the date and local time to evaluate.
- Select weather: Choose the cloud cover condition matching reality.
- Select surface type: Choose the surface environment (affects reflected UV).
- View results: Results update in real-time showing UV index, sunburn time, and protection advice.
Use Cases
Outdoor Sports Planning
Assess UV index before running, hiking, cycling to decide sun protection level and timing.
Travel Sun Protection
Understand destination UV index before traveling to tropical or high-altitude areas to prepare proper sun protection gear.
Skin Health Management
Sensitive skin individuals schedule outdoor time based on UV index to prevent UV allergies and sunburn.
Children's Outdoor Activities
Children's skin is more delicate; parents decide outdoor activities and protection based on UV index.
Background Knowledge
The UV Index is standardized by WHO. The core calculation uses solar zenith angle (θ), determined by latitude (φ), solar declination (δ), and hour angle (h): cosθ=sinφ×sinδ+cosφ×cosδ×cosh. Solar declination δ=23.45°×sin(360°×(284+N)/365), where N is the day of year. UV index≈12.5×cosθ×altitude correction×cloud correction×ozone correction. Altitude adds ~10% per km. Cloud factors: clear 1.0, few clouds 0.9, partly cloudy 0.75, cloudy 0.55, overcast 0.35. Sunburn time≈200/UV index (minutes, for fair skin).
FAQ
What is the UV Index?
The UV Index is an international standard measuring sun's UV radiation strength, ranging 0-11+. 0-2 low, 3-5 moderate, 6-7 high, 8-10 very high, 11+ extreme.
How is the UV Index calculated?
This tool estimates UV based on solar zenith angle (from latitude and time), altitude, cloud cover, and ozone attenuation.
When is UV index highest?
UV peaks at solar noon (11:00-13:00 local time). Summer noon UV is typically 2-4 times higher than winter.
How to choose SPF?
UV 3-5: SPF 15+, 6-7: SPF 30+, 8-10: SPF 50+, 11+: SPF 50+ and avoid sun exposure.
How does altitude affect UV?
UV increases ~10-12% per 1000m altitude. Thinner atmosphere at high altitudes absorbs less UV.