Sun safety

Sun Exposure & Vitamin D Timer

Estimate a reasonable sun exposure window based on your skin type and today's UV index, then start a countdown so you don't lose track of time outside.

—Suggested sun window
—Estimated time to burn
00:00Ready to start
Educational estimate only, not medical advice. Actual burn time depends on sunscreen, altitude, reflection, time of day and individual skin sensitivity. Never rely on this instead of proper sun protection.

Calculated on your device. Nothing is uploaded or stored on a server.

How to use the sun exposure & vitamin D timer

Choose your skin type from the Fitzpatrick scale and enter today's UV index (check your weather app). The tool estimates how long your skin can be exposed before burning and suggests a shorter window for vitamin D production, then lets you start a countdown timer for that window.

How the sun exposure window is estimated

Each Fitzpatrick skin type has an approximate reference time to sunburn at a UV index of 1, based on public sun-safety guidance. Dividing that reference time by today's UV index scales the estimate to current conditions, since higher UV shortens time to burn roughly proportionally. The suggested vitamin D window is set well below the burn estimate as a simple, conservative heuristic.

Vitamin D vs. burn risk

Some UV exposure helps the skin produce vitamin D, but the benefit plateaus quickly while burn risk keeps rising with longer exposure — so more time in the sun isn't better for vitamin D once you're past a short window.

Many factors aren't modeled

Sunscreen, cloud cover, altitude, water or snow reflection, clothing coverage and individual variation all change real-world burn time significantly.

Sun exposure & vitamin d timer FAQ

Common questions, answered.

How is time to burn estimated?

Each Fitzpatrick skin type has an approximate reference number of minutes to burn at UV index 1. That reference is divided by today's UV index to estimate time to burn under current conditions.

What is the Fitzpatrick skin type scale?

It's a classification of skin's sun sensitivity, from Type I (very fair, always burns, never tans) to Type VI (deeply pigmented, almost never burns), based on how skin typically responds to sun exposure.

Why is the suggested vitamin D window shorter than the burn estimate?

It's a conservative heuristic: most of the vitamin D benefit from sun exposure occurs well before burn risk becomes significant, so a shorter window is suggested to balance benefit against risk.

Does this account for sunscreen?

No. Sunscreen substantially extends safe exposure time. This estimate assumes bare, unprotected skin, so treat the numbers as a cautious baseline, not a hard limit if you're wearing sunscreen.

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