Tools / Vitamin D and sunlight

The minutes change.
Understand why.

A calculator to explore how the estimate changes with your location and your skin. There is no universal exposure time or guaranteed risk-free sun exposure.

01 / Set the scene

Where you are

Enter coordinates

Choose “Another location” and enter its coordinates and time zone.

LatitudeLongitudeTime zone

When Local time

Skin type

Age (adults)

Choosing a skin type

Based on your usual skin response: I always burns; II burns easily; III sometimes; IV rarely; V very rarely; VI almost never. This is an approximate classification, not a diagnosis. If unsure, compare scenarios without treating the result as permission to expose your skin.

Clothing

Sunscreen

Behind glass

Comparison reference

An illustrative reference, not your daily requirement or a supplement dose.

No account. Values appear in the URL: avoid sharing private coordinates.

02 / An estimate, in context

Madrid

25 Sep 2026
12:00 · Europe/Madrid
UTC+02:00

Duration of the calculated example

22min

The comparison fits within this example.

This is a limited mathematical scenario, not a safe time or personal recommendation. Do not extend exposure to reach the comparison.

Central estimate: 415 IU eq.
Illustrative range: 166–830 IU eq.
UV at the start: 3.1
Estimated exposed skin: 36.5%

What these numbers mean

IU equivalents are a model conversion, not measured vitamin D or a blood test result. The range reflects uncertainty assumptions; it is not a clinical confidence interval.

Weather forecast and model
Model confidence: medium. Clouds, shade, orientation and your individual response can change the result.

Assumptions in this calculation

A first session of the day, outdoors without shade, unless glass is selected. Previous exposure is not included.
At most 30 minutes and never beyond half the modelled time to redness without sunscreen. This does not guarantee an absence of damage.
Sunscreen reduces estimated production using a real-world approximation. It does not predict your SPF or extend the exposure limit.
Age introduces an uncertain adjustment. Skin type cannot capture all individual variation.
When clocks go back, the first occurrence of a repeated hour is used; the UTC offset is shown above.

Forecast generated: 2026-09-25T13:05:49Z. Weather data from MET Norway (The Norwegian Meteorological Institute). All-sky UV derived by Taiyo from MET clear-sky UV and cloud cover. CC BY 4.0. Taiyo model 2.0.0.

Use protection from UV 3. If you have photosensitivity, a skin condition or medication affecting your skin, consult your healthcare professional first. This tool cannot guide treatment decisions. WHO ↗

From numbers to context

The same question. Different days.

How many minutes of sun for vitamin D?

There is no single number for everyone. This calculator compares scenarios within the limits and uncertainty of Taiyo’s model. Your selected reference is not a daily requirement calculated for you.

Read the method and its limits ↗

Through glass · With sunscreen · In winter

Educational tool under review. It does not yet have independent clinical validation.