Iron Intake Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/6/2026
The percentage of recommended iron intake is calculated as (iron consumed ÷ reference intake) × 100. The reference intake is 11 mg/day for a man and 16 mg/day for a non-menopausal woman; with 8 mg consumed, a woman reaches 50% of her reference intake.
Explanation
Iron is a mineral essential for oxygen transport in the blood (it's a component of hemoglobin) and for many enzymatic reactions. The recommended dietary intake differs markedly by sex in adults: 11 mg per day for a man, versus 16 mg per day for a non-menopausal woman, an almost 50% higher requirement that reflects iron losses from menstruation. After menopause, a woman's requirement moves closer to a man's, since this higher need no longer applies; conversely, pregnancy increases it even further (up to 25-35 mg/day depending on the guidelines). Prolonged iron deficiency can lead to iron-deficiency anemia (fatigue, paleness, shortness of breath on exertion), the most common nutritional deficiency in the world, particularly among women of childbearing age and people following a strict vegetarian or vegan diet, since plant-based (non-heme) iron is less well absorbed by the body than animal-based (heme) iron.
Example: non-menopausal woman, 8 mg of iron consumed
Inputs
Iron consumed: 8 mg. Sex: non-menopausal woman (reference intake 16 mg/day).
Calculation
Percentage of reference intake = (8 ÷ 16) × 100 = 50%.
Result
This intake covers 50% of the recommended dietary iron intake for this profile.
Frequently asked questions
Why is the recommended iron intake higher for women than for men?
Because menstruation causes a regular loss of blood, and therefore iron, which the body must compensate for through higher dietary intake. This higher requirement (16 mg/day versus 11 mg/day for men) applies to non-menopausal women; after menopause, the reference intake moves closer to that of a man of the same age.
Which foods are the best sources of iron?
Animal-based iron (red meat, organ meats, blood sausage, seafood), called heme iron, is better absorbed by the body (10 to 30% of ingested iron) than plant-based iron (legumes, spinach, whole grains), called non-heme iron, whose absorption is lower and more variable (2 to 10%) but can be improved by pairing these foods with a source of vitamin C in the same meal.
How do I know if I really lack iron?
This calculator only gives an estimate based on self-reported dietary intake, not a diagnosis. An actual iron deficiency is confirmed by a blood test (notably a ferritin measurement), and persistent symptoms like unusual fatigue, shortness of breath on exertion, or paleness should be evaluated by a health professional rather than by this calculation alone.