Sunburn Time Estimator
Sunburn Time at UV 9 for Type II — Fair
Usually burns, tans minimally. At UV index 9 (very high), unprotected Type II skin is estimated to redden in 15 min – 23 min of direct midday sun. Values below assume clear-sky exposure, average skin baseline, and no sunscreen. Individual MED varies ±20%.
How this estimate is calculated
At UV 9, erythemal irradiance is about 225 mW/m². Type II skin has an MED near 250 J/m², so reaching one MED takes roughly 15–23 minutes of direct midday sun. The formula is: burn_minutes = MED (J/m²) ÷ (UV × 25 mW/m²) ÷ 60. This is the standard erythemal-dose calculation used by WHO INTERSUN and EPA SunWise. The ±20% band comes from person-to-person MED variation documented in Sayre 1981 and Diffey 2002.
With sunscreen at UV 9 for Type II
Most people apply about half the labeled sunscreen dose, which halves the effective SPF. DermUV bakes that into every estimate below:
| Sunscreen | Effective SPF | Est. protected time |
|---|---|---|
| None | 1 | 15 min – 23 min |
| SPF 15 broad-spectrum | ~7.5 | 2h 23m |
| SPF 30 broad-spectrum | ~15 | 4h 45m |
| SPF 50 broad-spectrum | ~25 | 7h 55m |
Reapply every 80 minutes outdoors, and immediately after swimming, sweating, or towelling. AAD recommends a minimum of SPF 50 broad-spectrum at UV 9.
What UV 9 means for Type II skin
Extra precautions. Avoid sun 10am–4pm, use SPF 50+. Type I and II skin lacks the eumelanin that shields deeper cells from UVB, which is why redness starts fastest here. A burn at this exposure counts toward lifetime melanoma risk, which roughly doubles after a single blistering childhood burn (Skin Cancer Foundation).
Related sunburn-time pages
Educational estimates from WHO INTERSUN and Fitzpatrick MED literature. Not a substitute for a dermatologist.
Using Sunburn Time at UV 9 — Skin Type 2 in practice
UV strength on this page follows solar elevation, ozone thickness, cloud cover, altitude, and surface reflection. Snow can bounce back most of the UV that hits it, water and sand far less, but all of them add to the dose skin receives.
Burn-time figures come from minimal erythemal dose (MED) values published for each Fitzpatrick skin type, divided by the erythemal irradiance at a given UV index. Personal MED varies by roughly 20 percent, so treat every number as a planning range.
Reapplication matters more than the SPF number. Reapply roughly every two hours outdoors and immediately after swimming, heavy sweating, or towelling, regardless of what the bottle claims.
Cumulative dose drives photoaging and long-term skin damage more than any single day. Small daily exposures on commutes, walks, and driving add up across a season.
Plan outdoor blocks around the peak UV window, usually between 10am and 4pm local time. Shade, UPF fabric, a wide-brim hat, and UV-blocking sunglasses reduce dose more reliably than sunscreen alone.
UV scale reference
The WHO scale groups UV 1-2 as low, 3-5 as moderate, 6-7 as high, 8-10 as very high, and 11 or above as extreme. Protection is recommended from UV 3 upward, and shade during the middle of the day becomes the priority from UV 8 upward.
A practical routine at moderate-to-high UV is roughly one ounce of broad-spectrum sunscreen for full-body coverage, applied 15 minutes before going out, then reapplied on schedule. Clothing, hats, and shade carry the rest of the load, especially for children and anyone with a history of easy burning.
Keep exploring DermUV
These pages give more depth around sunburn time at uv 9 — skin type 2, from UV-scale reference material to calculators and city forecasts.
- UV index by city
- Tan vs burn calculator
- Do I need sunscreen?
- UV and sunscreen calculators
- UVA definition
- reflection lesson
- SPF definition
- What UV index 3 means
- spf math lesson
Numbers are modelled, not measured at your exact location, so treat them as guidance for planning rather than exact thresholds.