The Taiyo method
Trust starts with explaining the limits.
Forecasts and estimates can help. Knowing where they come from is part of using them well.
The weather data
The website tool uses the same UV service as the app. It starts with MET Norway forecasts when available and combines hourly data with solar-position calculations. Cloud cover is applied when the data supports it; it is not corrected twice.
When data is missing
Gaps are filled using a clear-sky model based on Allaart and an ozone climatology. Without cloud data, estimates may not reflect actual conditions. The tool displays the source and confidence of each hour.
UV is not your vitamin D
The website’s UV values describe environmental conditions. The app and web calculator add skin type, clothing, time and duration to estimate vitamin D production. Solar IU are approximate model equivalents, not a measured intake or a way to know your blood levels.
No clinical promise
Taiyo does not present its estimates as clinically validated. Individual responses and actual conditions may differ from the model’s assumptions. An alert or timer cannot guarantee the absence of sun damage.
Sources and editorial responsibility
The Taiyo team at Utropia writes the content. Guides link to the sources supporting their claims. Before publication for search engines, health content requires a qualified review with a name, credentials and date. We do not claim medical endorsements that do not exist.
Open to corrections
If you notice an error or an outdated source, please write to us. Source-checking dates and professional-review dates are distinct. Updates should explain what changed and why.
The public calculator
It uses Taiyo’s vitamin D model 2.0.0 with minute-by-minute integration. It adds a 30-minute limit and retains the redness limit without extending it for sunscreen. The 200, 400 or 600 IU-equivalent reference is for comparison, not your daily requirement. Displayed confidence never exceeds that of the available UV data. The range is illustrative, not a validated clinical interval.
Explore the calculator ↗Consult the sources