Vitamin D From Sun Calculator
A rough educational estimate of how many minutes of midday sun it takes to make vitamin D for your skin type.
How it works
minutes ≈ 15 × skin factor × (3 ÷ UV index) × (0.25 ÷ exposed fraction)
Sunlight in the UVB range converts a skin precursor into vitamin D, but the amount depends on skin pigment, how much skin is bare, UV intensity, season, latitude and age — so any single number is only a rough guide. This tool starts from an often-cited baseline (a light-skinned person making around 1,000 IU from roughly 15 minutes of moderate midday sun on face and arms) and scales it. Darker skin needs substantially longer, and once skin starts to redden no extra vitamin D is made — only sun damage.
Worked example
Type III skin, UV index 6, arms exposed (~25%): minutes ≈ 15 × 1 × (3 ÷ 6) × (0.25 ÷ 0.25) = 7.5 minutes for about 1,000 IU.
Frequently asked questions
How accurate is this estimate?
Only broadly. Vitamin D synthesis varies enormously between people and conditions, so treat the result as an order-of-magnitude guide, not a prescription. A blood test is the only way to know your actual level.
Can I get too much vitamin D from the sun?
Your skin self-limits production, so sun will not cause vitamin D toxicity — but it will cause burns and skin-cancer risk. Supplements, not sun, are where overdose is possible.
What about sunscreen and vitamin D?
Sunscreen reduces UVB and therefore synthesis, but in practice people apply too little to block it entirely. Most experts favor sun protection plus diet or supplements over deliberate unprotected exposure.
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This is a general educational estimate, not medical advice. Individual responses vary — for decisions about exercise, sun exposure, heat, cold or health conditions, talk to a qualified professional.