Iron RDA Calculator
Iron is an essential mineral required for haemoglobin synthesis, oxygen transport, and energy metabolism. Iron needs differ significantly by sex and life stage because of menstrual blood losses and pregnancy demands. The NIH Office of Dietary Supplements sets the RDA at 8 mg per day for adult men and post-menopausal women, 18 mg per day for women aged 19-50, and 27 mg per day during pregnancy. Vegetarians and vegans should target 1.8 times the standard RDA due to lower bioavailability of non-heme iron. The tolerable upper intake level (UL) is 45 mg per day. Enter your daily iron intake and select your demographic to compare against your RDA and the UL.
Iron RDA values (NIH ODS)
% of RDA = Intake (mg) / RDA (mg) * 100
RDA: men/post-meno 8 mg, women 19-50: 18 mg,
pregnant 27 mg, breastfeeding 9 mg
Tolerable Upper Level (UL): 45 mg/day
Vegetarian/vegan: multiply RDA by 1.8
Values from the NIH Office of Dietary Supplements Iron Fact Sheet. Vegetarian and vegan targets are derived by applying the 1.8x bioavailability adjustment factor recommended by the National Academies.
Optimising iron intake
- Eat heme iron sources (meat, seafood) with non-heme sources to improve overall absorption.
- Pair non-heme iron foods with vitamin C (e.g., orange juice with iron-fortified cereal) to enhance absorption.
- Avoid drinking tea or coffee with iron-rich meals, as polyphenols inhibit iron absorption.
- Cooking in cast iron cookware can add small amounts of dietary iron, particularly in acidic dishes like tomato sauce.
- Iron supplementation should be guided by a healthcare provider; excess iron from supplements can be harmful and symptoms may mask other conditions.
Iron RDA calculator: frequently asked questions
How much iron do I need per day?
The NIH ODS RDA for iron is 8 mg/day for adult men (19+) and 18 mg/day for women aged 19-50 (due to menstrual losses). Post-menopausal women need only 8 mg/day. Pregnant women need 27 mg/day. Vegetarians and vegans may need 1.8 times the standard RDA because non-heme iron from plants is less bioavailable than heme iron from meat.
What is the tolerable upper intake level (UL) for iron?
The UL for iron in adults is 45 mg per day from all sources combined. Amounts above the UL increase the risk of gastrointestinal distress, and very high doses can cause iron toxicity. Accidental iron overdose is a leading cause of poisoning in young children.
What are good sources of iron?
Heme iron (most bioavailable) is found in meat, poultry, and seafood: 3 oz beef (2.1 mg), 3 oz oysters (8 mg). Non-heme iron sources include fortified cereals (up to 18 mg per serving), white beans (8 mg per cup), lentils (3.3 mg per 1/2 cup), spinach (3.2 mg per 1/2 cup cooked), and tofu (3 mg per 1/2 cup).
What increases iron absorption?
Consuming vitamin C alongside non-heme iron foods significantly increases absorption. Heme iron from meat is absorbed at 15-35%, while non-heme iron is absorbed at only 2-20% depending on iron status and diet composition. Phytates (in whole grains), polyphenols (in tea/coffee), and calcium reduce iron absorption.
What are the signs of iron deficiency?
Iron deficiency anaemia causes fatigue, weakness, pale skin, shortness of breath, cold hands and feet, unusual cravings for non-food items (pica), and brittle nails. Iron deficiency without anaemia can cause fatigue and impaired cognitive function. A blood ferritin test is the most sensitive marker of iron stores.
Official sources
- NIH Office of Dietary Supplements: Iron Fact Sheet for Health Professionals.
- USDA FoodData Central: FoodData Central (iron content per food).
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.