Iron Intake Calculator
Calculate your recommended daily iron intake by age, sex, and life stage, with adjustment for vegetarian and vegan diets where non-haem iron is absorbed less efficiently.
🩸 Nutrition📐 RDA: 8–27 mg/day depending on age, sex, and life stage🏥 Health
Sex
Age (years)
Life stage
Diet type
Please enter valid values.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| Iron Intake Calculator | — | RDA: 8–27 mg/day depending on age, sex, and life stage | mg/day |
Step-by-Step Examples
Example 1
Adult Man
32-year-old man, mixed diet.
- RDA for men 19 and over: 8 mg/day
- No vegetarian adjustment applied
✓ 8 mg/day
Example 2
Menstruating Woman
32-year-old woman, mixed diet.
- RDA for women 19–50: 18 mg/day
- Higher than men due to menstrual iron losses
✓ 18 mg/day
Example 3
Pregnant Vegetarian
30-year-old pregnant woman, vegetarian.
- Pregnancy RDA: 27 mg/day
- Vegetarian adjustment: 27 × 1.8 = 48.6 mg/day
- This exceeds the 45 mg upper limit — medical guidance is essential here
✓ About 49 mg/day — requires clinician input
Real-World Applications
Menstrual Losses
The RDA for menstruating women is more than double that for men, reflecting monthly iron loss.
Pregnancy Demands
Pregnancy raises iron requirements to 27 mg/day to support expanded maternal blood volume and fetal needs.
Plant-Based Diets
Non-haem iron from plants is absorbed far less efficiently, which is why vegetarian requirements are set roughly 1.8 times higher.
Absorption Enhancers
Vitamin C consumed alongside plant iron sources can substantially increase absorption from the same meal.
Common Mistakes to Avoid
⚠️
Taking iron supplements without testing
Iron overload is genuinely harmful and undiagnosed haemochromatosis is not rare. Supplementation should follow a confirmed deficiency, not a hunch.
⚠️
Pairing iron with tea, coffee, or calcium
Tannins, polyphenols, and calcium all inhibit iron absorption substantially when consumed with the same meal. Separating them by a couple of hours helps.
⚠️
Assuming spinach is a great iron source
Spinach contains iron but its oxalate content severely limits absorption. Legumes, fortified cereals, and tofu deliver far more usable iron.
Frequently Asked Questions
How much iron do I need daily? ▾
Adult men need 8 mg, menstruating women 18 mg, pregnant women 27 mg, and postmenopausal women 8 mg per day.
Why do vegetarians need more iron? ▾
Plant foods contain non-haem iron, which is absorbed at a much lower rate than the haem iron in meat — so requirements are set roughly 1.8 times higher.
What helps iron absorption? ▾
Vitamin C is the most effective enhancer. Cooking in cast iron adds a small amount, and avoiding tea, coffee, and calcium at the same meal helps considerably.
Can I take too much iron? ▾
Yes. The adult upper limit is 45 mg/day, and excess iron causes gastrointestinal distress acutely and organ damage over time in overload states.
Should I get tested before supplementing? ▾
Yes. Ferritin and transferrin saturation identify whether you are actually deficient, and in adults a deficiency also warrants investigating why.