Burnline
How long you can stay out before you burn — for your skin, your sunscreen, and the sun actually above you right now.
Your sky, not a national average
Burnline computes the sun's angle from your exact position and altitude, then converts it to erythemal dose using the CIE Standard Erythema Dose and the minimal erythema dose for your Fitzpatrick skin type. It runs entirely on your device — no network, no account.
Honest about sunscreen
Burnline never assumes your SPF works as labelled. Real-world application is a third to a half of the laboratory thickness, so the app uses a conservative effective SPF. Telling you that SPF 50 multiplies your time by 50 is how somebody gets burned holding a phone.
Private by construction
Your coordinates are used to do maths on your phone and are never transmitted. No analytics, no tracking, no servers. See the privacy policy.
Burnline is an informational tool, not a medical device. It is not a substitute for medical advice or for standard sun-safety practice. See the terms of use.