Sun Tan Calculator
Find how long you can safely sit in the sun to tan without burning. Based on the Fitzpatrick skin type scale, UV index, and SPF protection.
Frequently Asked Questions
How is the safe tanning time calculated?
The calculator uses the Fitzpatrick skin type scale to determine your Minimal Erythemal Dose (MED) — the UV dose needed to cause the first visible skin reddening. Your safe tanning window is approximately 60% of that MED time, and your burn threshold is 100%. Both are divided by the UV index and multiplied by your SPF factor.
What is the UV index?
The UV index (UVI) is an international scale from 1 (low) to 11+ (extreme) that measures the intensity of ultraviolet radiation at the earth's surface. A UV index of 6 or above is considered high and requires sun protection. You can find the current UV index in most weather apps or on weather service websites.
Does sunscreen prevent tanning?
Sunscreen significantly reduces the UV radiation reaching your skin, which delays both tanning and burning. High-SPF products can extend your safe exposure time considerably. However, dermatologists recommend SPF 30 or higher for all outdoor activities to reduce the long-term risk of skin damage and skin cancer, regardless of skin type.
What time of day is UV radiation strongest?
UV radiation is most intense between 10 am and 4 pm, peaking around solar noon (typically 12–2 pm depending on your location and time of year). During these hours the sun is highest in the sky and UV travels through the least atmosphere. Outside this window — early morning or late afternoon — UV intensity drops significantly, making it a safer time for sun exposure.
What is the Fitzpatrick skin type scale?
The Fitzpatrick scale, developed by dermatologist Thomas Fitzpatrick in 1975, classifies skin into six types based on its reaction to UV exposure. Type I always burns and never tans; Type II usually burns and tans minimally; Type III sometimes burns and tans gradually; Type IV rarely burns and tans easily; Type V very rarely burns and tans very easily; Type VI never burns and is deeply pigmented. The scale is widely used in dermatology to assess sun sensitivity and skin cancer risk.
Can I get vitamin D while wearing sunscreen?
Yes, but in smaller amounts. Sunscreen reduces UVB radiation, which is the type your skin needs to synthesise vitamin D. In practice, most people do not apply sunscreen perfectly — missed patches and partial coverage mean some UVB still reaches the skin. A few minutes of unprotected sun exposure on the arms or legs before applying sunscreen is enough for most people to produce adequate vitamin D. Those with darker skin types or who live at higher latitudes may need longer exposure or dietary supplementation.