Daily Iron Intake Calculator
Find daily iron intake in mg from age, sex, pregnancy status, and diet type.
Returns NIH RDA, top food sources by mg per serving, and absorption tips.
Iron intake requirements vary significantly by age, sex, and physiological status. Iron is essential for hemoglobin synthesis, oxygen transport, and cellular energy metabolism. Both deficiency (the most common nutritional deficiency worldwide) and excess cause serious health consequences.
Dietary iron absorption formula: Absorbed Iron (mg) = Total Dietary Iron × Absorption Rate
Absorption rates:
- Heme iron (from meat, poultry, fish): 15–35% absorption
- Non-heme iron (from plants, fortified foods): 2–20% absorption
- With vitamin C (50+ mg concurrent): absorption increases 2–4×
- With calcium, tannins (tea/coffee), phytates (grains): absorption decreases 30–60%
Daily iron requirements (RDA, National Institutes of Health):
| Group | Daily RDA |
|---|---|
| Infants (0–6 months) | 0.27 mg |
| Infants (7–12 months) | 11 mg |
| Children (1–8 years) | 7–10 mg |
| Males (14–18) | 11 mg |
| Males (19+) | 8 mg |
| Females (14–18) | 15 mg |
| Females (19–50) | 18 mg |
| Females (51+) | 8 mg |
| Pregnant women | 27 mg |
| Breastfeeding women | 9–10 mg |
Iron deficiency anemia threshold: Hemoglobin < 12 g/dL (women), < 13 g/dL (men). Ferritin < 12 ng/mL confirms depleted iron stores.
Worked example: A 28-year-old vegetarian woman needs 18 mg/day (RDA). Non-heme iron lunch: 1 cup lentils (6.6 mg) + 1 cup spinach (3.7 mg) = 10.3 mg total. Absorption without vitamin C: 10.3 × 0.08 = 0.82 mg absorbed With orange juice (70 mg vitamin C): absorption rate triples → 10.3 × 0.24 = 2.47 mg absorbed — three times more iron from the same meal.
This highlights why pairing plant-based iron sources with vitamin C is critical for vegetarians and vegans who lack heme iron sources.