How long unprotected skin can take today's sun, for every Fitzpatrick type. The table uses the same formula as the live dashboard and every city page: minutes = MED ÷ (UVI × 1.5).
| Skin type | UV 3 | UV 5 | UV 6 | UV 8 | UV 10 | UV 11 | UV 12 |
|---|---|---|---|---|---|---|---|
| I · always burns, never tans | 44 min | 27 min | 22 min | 17 min | 13 min | 12 min | 11 min |
| II · burns easily | 56 min | 33 min | 28 min | 21 min | 17 min | 15 min | 14 min |
| III · burns sometimes | 1 h 18 min | 47 min | 39 min | 29 min | 23 min | 21 min | 19 min |
| IV · rarely burns | 1 h 40 min | 1 h | 50 min | 38 min | 30 min | 27 min | 25 min |
| V · brown skin | 2 h 13 min | 1 h 20 min | 1 h 07 min | 50 min | 40 min | 36 min | 33 min |
| VI · deeply pigmented | 3 h 42 min | 2 h 13 min | 1 h 51 min | 1 h 23 min | 1 h 07 min | 1 h 01 min | 56 min |
SPF multiplies unprotected time by its rating when a full test layer is applied. At UV 8, type II goes from about 21 min unprotected to about 10 h 25 min with SPF 30 in lab conditions.
Most people apply roughly a third of that layer. Treat protected times as a ceiling and reapply.
| I · always burns, never tans | 200 J/m² |
| II · burns easily | 250 J/m² |
| III · burns sometimes | 350 J/m² |
| IV · rarely burns | 450 J/m² |
| V · brown skin | 600 J/m² |
| VI · deeply pigmented | 1000 J/m² |
UV index 1 equals 0.025 W/m² of erythemal irradiance. Unprotected skin reaches its minimal erythemal dose (MED) in minutes = MED ÷ (UVI × 1.5). MED depends on Fitzpatrick skin type: type I is 200 J/m², type II 250, type III 350, type IV 450, type V 600, type VI 1000. Sunscreen multiplies the result by its SPF rating.
At UV 8 with no sunscreen: type I about 17 min, type II about 21 min, type III about 29 min, type VI about 1 h 23 min. Those are the same numbers the live dashboard shows.
In a lab, yes: SPF multiplies burn time by its rating when a full 2 mg/cm² layer is applied. Real-world application is usually about a third of that test layer, so treat any protected time as a ceiling, not a promise. Reapply, don't rely on the number.
Type I always burns and never tans; type II burns easily and tans minimally; type III burns moderately and tans gradually; type IV burns minimally and tans well; type V rarely burns and tans deeply; type VI almost never burns. If you are between two types, use the fairer one — the site errs toward caution.
uvlevel.net gives general sun-safety guidance, not medical advice. Photosensitising medication, skin conditions, infants and a history of skin cancer all call for stricter limits than shown here.