Micronutrient calculator

The numbers below are the Dietary Reference Intakes (DRIs) set by the National Academies and published by the NIH Office of Dietary Supplements. Three terms do most of the work, and they are easy to confuse:

• RDA (Recommended Dietary Allowance) — the daily intake that meets the needs of ~97.5% of healthy people in a given age and sex group. This is the target to aim for. Where the science isn't strong enough to set an RDA, an AI (Adequate Intake) is used instead (vitamin K, potassium, sodium).
• UL (Tolerable Upper Intake Level) — the highest daily intake unlikely to cause harm. The gap between the RDA and the UL is your safe range; routinely exceeding the UL (almost always via supplements, not food) is where risk starts. Several nutrients have no established UL.
• %DV (Percent Daily Value) — the single reference number on a food label. It is deliberately one-size-fits-all (generally the highest adult RDA), so it over- or under-states the target for most individuals. The calculator replaces it with your RDA.

Why needs vary. Iron requirements roughly double for menstruating women (18 mg vs 8 mg) and jump to 27 mg in pregnancy. Folate rises to 600 mcg in pregnancy to support neural-tube development. Calcium and vitamin D climb in older adults to protect bone. Vitamin B6 increases after 50. The calculator applies these age, sex, and life-stage adjustments from the DRI tables.

Plant-based diets. Two requirements genuinely change. The iron RDA is set 1.8× higher for vegetarians and vegans because plant (non-heme) iron absorbs at roughly 10% versus 18% on a mixed diet, and zinc may need to be up to 50% higher because phytates impair absorption — both per the NIH Office of Dietary Supplements. Vitamin B12 is different: the requirement is identical, but there is no reliable plant source, so vegans need fortified foods or a supplement. Iodine, vitamin D, and calcium are similarly flagged as source problems, not higher numbers. Choosing a diet pattern applies the iron and zinc adjustments and surfaces these notes.

Units note. Vitamin A is shown in mcg RAE (retinol activity equivalents), niacin in mg NE (niacin equivalents), and folate in mcg DFE (dietary folate equivalents) — the modern bioavailability-adjusted units used by the DRIs. The vitamin A and folate ULs apply to preformed retinol and synthetic folic acid respectively, not to the forms found naturally in food.

Not medical advice. These are population reference intakes for healthy people, not a prescription. Medical conditions, medications, malabsorption, and individual lab values can change your needs substantially. Talk to a doctor or registered dietitian before starting supplements, especially anything approaching a UL.