Vitamin D Calculator

Estimate vitamin D from sun, food and supplements — see total IU, % of RDA and safe upper limit.

Vitamin D Calculator

Estimate vitamin D from sun, food and supplements — see total IU, % of RDA and safe upper limit.

Sun exposure (minutes/day)

Food vitamin D (IU/day)

Supplement (IU/day)

Enter values above and click Calculate — results will appear here with the formula explained.

Total = sun*~8 IU per minute (midday, fair skin, arms/legs) + food + supplement; RDA 600 IU (19-70), 800 (71+)

How does this work?

Midday sun on arms/legs for fair skin makes roughly 8-25 IU per minute, highly variable with latitude, season, skin tone and sunscreen. Food contributes modestly (fatty fish, fortified milk).

RDA is 600 IU for adults 19-70 and 800 for 71+, upper limit 4000 IU. This is general information, not medical advice — test levels for personal dosing.

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Disclaimer: Results are estimates for informational purposes only and do not constitute professional medical advice.

Quick Answer

Vitamin D Calculator: Estimate vitamin D from sun, food and supplements — see total IU, % of RDA and safe upper limit. Formula: Total = sun*~8 IU per minute (midday, fair skin, arms/legs) + food + supplement. Example: With 15 min sun.

How to Use This Calculator

1Enter average daily sun minutes (exposed skin), food IU and supplement IU.
2Calculate to see total IU, % of RDA and upper limit check.
3If vs 600 IU low, consider food/supplement — winter and darker skin need more.

Formula Used

Total = sun*~8 IU per minute (midday, fair skin, arms/legs) + food + supplement; RDA 600 IU (19-70), 800 (71+)

Midday sun on arms/legs for fair skin makes roughly 8-25 IU per minute, highly variable with latitude, season, skin tone and sunscreen. Food contributes modestly (fatty fish, fortified milk).

RDA is 600 IU for adults 19-70 and 800 for 71+, upper limit 4000 IU. This is general information, not medical advice — test levels for personal dosing.

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Worked Example

With 15 min sun (~120 IU) + 200 IU food + 1000 IU supplement = ~1320 IU, 220% of 600 IU RDA, under 4000 IU upper limit.

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Frequently Asked Questions

QDoes sunscreen block?

Sunscreen reduces synthesis ~90%, but protects from cancer. Don't sunburn for vitamin D.

QDarker skin?

Melanin reduces synthesis, requiring 2-3× longer sun for similar IU — food/supplement more important.

QCan I overdose?

Over 4000 IU/day long term risks hypercalcemia. Food alone rarely exceeds.

Formula Used

Total = sun*~8 IU per minute (midday, fair skin, arms/legs) + food + supplement; RDA 600 IU (19-70), 800 (71+)

Midday sun on arms/legs for fair skin makes roughly 8-25 IU per minute, highly variable with latitude, season, skin tone and sunscreen. Food contributes modestly (fatty fish, fortified milk).

RDA is 600 IU for adults 19-70 and 800 for 71+, upper limit 4000 IU. This is general information, not medical advice — test levels for personal dosing.

Frequently Asked Questions

QDoes sunscreen block?

Sunscreen reduces synthesis ~90%, but protects from cancer. Don't sunburn for vitamin D.

QDarker skin?

Melanin reduces synthesis, requiring 2-3× longer sun for similar IU — food/supplement more important.

QCan I overdose?

Over 4000 IU/day long term risks hypercalcemia. Food alone rarely exceeds.