Vitamin D Calculator
The Vitamin the Body Can Make for Itself
Vitamin D is unusual among vitamins because the body synthesizes it from sun exposure on skin, on top of what's absorbed from food. That dual source makes fixed daily intake recommendations more of a dietary safety net than the whole picture, but the Institute of Medicine RDA and AI figures still serve as the standard reference point for how much should come from diet and supplementation.
Recommended Daily Intake
| Age group | IU/day | mcg/day |
|---|---|---|
| Infants, 0–12 months | 400 | 10.0 |
| Ages 1–70 (including pregnancy/lactation) | 600 | 15.0 |
| Ages 71+ | 800 | 20.0 |
Conversion: 1 microgram (mcg) of vitamin D equals 40 International Units (IU).
The Formula
mcg/day = IU/day ÷ 40
Why the Target Rises With Age
- Reduced skin synthesis — the skin's ability to produce vitamin D from sunlight declines with age, raising the dietary recommendation for older adults.
- Bone health — vitamin D supports calcium absorption, making adequate intake particularly relevant for bone density maintenance later in life.
- Limited sun exposure — people who spend most of their time indoors, live at higher latitudes, or have more skin pigmentation synthesize less vitamin D from sunlight and rely more on dietary intake.
How to Use This Calculator
- Enter your age.
- Indicate whether you are pregnant or lactating.
- Select Calculate to see your recommended daily vitamin D intake in both IU and mcg.
Related Calculations
Check other micronutrient targets with the Iron Calculator or Potassium Calculator.