Vitamin D Calculator
Find out how much Vitamin D you need daily based on your age, sun exposure, skin tone, and where you live.
What is Vitamin D and why does it matter?
Vitamin D is a fat-soluble vitamin that your body produces when skin is exposed to UVB sunlight. It plays a critical role in calcium absorption, bone health, immune function, and muscle strength. Unlike most vitamins, you can get a significant portion of your needs from sun exposure alone — but most people in modern life don't get enough.
Vitamin D deficiency is one of the most common nutritional deficiencies worldwide, affecting an estimated 1 billion people. Risk is highest in people who spend most of their time indoors, live at high latitudes, or have darker skin tones that require more sun exposure to synthesize adequate amounts.
Recommended daily intake by age group
| Age group | RDA (IU) | RDA (μg) | Upper limit |
|---|---|---|---|
| Infants 0–12 months | 400 IU | 10 μg | 1,000 IU |
| Children 1–13 years | 600 IU | 15 μg | 2,500–3,000 IU |
| Teens 14–18 years | 600 IU | 15 μg | 4,000 IU |
| Adults 19–70 years | 600 IU | 15 μg | 4,000 IU |
| Adults 71+ years | 800 IU | 20 μg | 4,000 IU |
| Pregnant / breastfeeding | 600 IU | 15 μg | 4,000 IU |
Signs of Vitamin D deficiency
- Fatigue and low energy that doesn't improve with rest
- Frequent infections or getting sick often
- Bone pain or lower back pain
- Muscle weakness or aches
- Low mood or depression, especially in winter
- Slow wound healing
- Hair loss (in severe cases)
The only way to confirm deficiency is a blood test measuring 25-hydroxyvitamin D (25(OH)D). Levels below 20 ng/mL are generally considered deficient; 20–29 ng/mL is insufficient; 30–100 ng/mL is sufficient for most people.
Best food sources of Vitamin D
- Fatty fish: Salmon (~570 IU/100g), mackerel (~360 IU/100g), sardines (~270 IU/100g)
- Fortified foods: Milk (~120 IU/cup), orange juice (~140 IU/cup), cereal (~40–100 IU/serving)
- Egg yolks: ~40 IU per egg
- Beef liver: ~50 IU/100g
- UV-exposed mushrooms: Variable, can be high if sun-dried
Food alone is rarely sufficient to meet Vitamin D needs. Supplementation is often recommended for people with limited sun exposure, especially in winter months above 35° latitude.