Vitamin Dosage Calculator
Nine Vitamins, One Lookup
Recommended Dietary Allowances for vitamins aren't single universal numbers — they're broken out by age bracket and sex, published by the NIH Office of Dietary Supplements. Most people encounter these figures as a single rounded number on a supplement label; this calculator instead looks up the specific value that applies to your actual age and sex for nine commonly tracked vitamins.
The Method
Rather than a formula, this calculator performs a table lookup against NIH Office of Dietary Supplements Recommended Dietary Allowance data, matching your age into the correct bracket (0–3, 4–8, 9–13, 14–18, 19–50, and 51+, with some vitamins using slightly different bracket boundaries) and returning the RDA for your sex within that bracket.
Adult RDA Reference (Ages 19–50 and 51+)
| Vitamin | Unit | 19–50, Male | 19–50, Female | 51+, Male | 51+, Female |
|---|---|---|---|---|---|
| Vitamin A | mcg RAE | 900 | 700 | 900 | 700 |
| Vitamin C | mg | 90 | 75 | 90 | 75 |
| Vitamin D | mcg | 15 | 15 | 15* | 15* |
| Vitamin E | mg | 15 | 15 | 15 | 15 |
| Vitamin K | mcg | 120 | 90 | 120 | 90 |
| Vitamin B6 | mg | 1.3 | 1.3 | 1.7 | 1.5 |
| Vitamin B12 | mcg | 2.4 | 2.4 | 2.4 | 2.4 |
| Folate | mcg DFE | 400 | 400 | 400 | 400 |
| Thiamin (B1) | mg | 1.2 | 1.1 | 1.2 | 1.1 |
*Vitamin D stays at 15 mcg/day through age 70 in this calculator's table and rises to 20 mcg/day only from age 71 onward — its bracket boundary sits at 70, not 50, unlike the other vitamins here. Vitamin B6 is the other notable exception: it rises after 50 rather than staying flat.
Why the Brackets Shift
- Growth years (0–18) — requirements climb steadily through each childhood and adolescent bracket as the body's needs increase with growth.
- Sex differences emerge at puberty — several vitamins show matched male/female values in early brackets that diverge starting at the 14–18 bracket.
- Later-life adjustments — Vitamin B6 and Vitamin D both increase in older age brackets, reflecting reduced absorption or synthesis efficiency with age.
How to Use This Calculator
- Select a Vitamin from the dropdown (A, C, D, E, K, B6, B12, Folate, or Thiamin/B1).
- Enter your Age.
- Select Male or Female for Gender.
- Select Calculate for the Recommended Dietary Allowance that applies to you.
Related Calculations
To check specific mineral intake against RDA targets rather than vitamins, use the Micronutrient Tracker Calculator. For fiber, which uses a similar age-bracket lookup, see the Fiber Intake Calculator.