What Vitamin D does
Vitamin D helps the body absorb calcium and supports bone health and immune function. It can come from sunlight exposure, fortified foods, and supplements, and is measured in either International Units (IU) or micrograms (mcg).
How this calculator works
Select your age group to see the standard Recommended Dietary Allowance (RDA), based on published national nutrition guidelines. The calculator also converts between IU and micrograms using the standard factor of 1 mcg = 40 IU, and shows what percentage of the RDA your entered intake represents.
This tool is for general educational purposes only. Vitamin D needs can vary with sun exposure, skin tone, and health status, and high-dose supplementation should be discussed with a physician, especially before exceeding standard upper intake limits.