UV Index & Safe Sun Exposure Time Estimator

How it works

The model is deliberately simple and is stated here in full so you can see exactly what the number means. Each skin type is given a reference time to burn, in minutes, at a UV index of 3: Type I 15 minutes, Type II 20 minutes, Type III 30 minutes, Type IV 40 minutes, Type V 60 minutes, and Type VI 90 minutes. Those are planning values, not measurements of your own skin.

The estimated safe time is then: reference time multiplied by (3 divided by the UV index), multiplied by a sunscreen factor. The sunscreen factor is 1 with no sunscreen, 5 for SPF 30, and 8 for SPF 50. These are conservative, effective-use factors — much lower than the labelled SPF numbers — because sunscreen is often applied too thinly, rubbed off, or washed off by swimming and sweat. The result is capped at 180 minutes, because no sunscreen result should be read as "safe all day".

For example, Type III skin at UV 8 with SPF 30 gives 30 × (3 ÷ 8) × 5 = 56 minutes. Without sunscreen the same case gives only 11 minutes. That gap is the point of the tool: on high-UV beach days, unprotected skin can burn far faster than it feels like it should.

How to use your result

Treat the number as a maximum to stay well inside, not a target. Seek shade, wear a hat and protective clothing, and reapply sunscreen at least every two hours — and sooner after swimming, towelling, or heavy sweating — even if the estimated time has not run out. If the UV index is 8 or higher, or the window is under 15 minutes, plan shade breaks and cover up rather than relying on sunscreen alone. Children, people with a history of skin cancer, and anyone taking medicines that increase sun sensitivity should be more cautious still and follow a clinician's advice.

Related guides

• The UV Index, Explained: How to Read It Daily
• Safe Sun Times for Every Skin Type
• Sunscreen Myths That Lead to Burns