Iron Absorption Calculator
Non-heme iron absorption depends on what else is on the plate — vitamin C helps, tea and coffee hurt.
Your meal
Plant iron sources
- Lentils, 1 cup cooked6.6 mg
- Tofu (firm), 100 g5.4 mg
- Pumpkin seeds, 30 g4.2 mg
- Chickpeas, 1 cup cooked4.7 mg
- Spinach, 1 cup cooked6.4 mg
- Cashews, 30 g1.9 mg
- Dark chocolate, 30 g3.4 mg
- Quinoa, 1 cup cooked2.8 mg
Vitamin C boosters
- Red bell pepper, ½95 mg
- Strawberries, 1 cup85 mg
- Orange, 1 medium70 mg
- Broccoli, 1 cup cooked100 mg
- Kiwi, 1 fruit65 mg
- Lemon juice, 2 tbsp12 mg
How this is calculated
Baseline: non-heme iron is absorbed at ~10%.
Vitamin C boost: multiplier = 1 + (mg C ÷ 50), capped at 3×. This matches published dose-response curves — the effect plateaus above ~100 mg.
Tea/coffee penalty: polyphenols cut absorption by roughly half at the same meal.
Estimates only. Real absorption also depends on iron status, calcium, phytates, and cooking method.
Frequently asked
Why do plant eaters need more iron?+
Plant (non-heme) iron is absorbed at only ~10% by default, compared to ~25% for heme iron in meat. The RDA reflects this: 18 mg/day for adult women, 8 mg for men — and the Institute of Medicine suggests plant-only eaters aim for ~1.8× that (~32 mg for women).
How much does vitamin C boost iron absorption?+
50 mg of vitamin C at the same meal roughly doubles non-heme iron absorption; 100+ mg can triple it. Half a red bell pepper, 1 cup of strawberries, or a squeeze of lemon over a lentil bowl is enough.
Do tea and coffee really block iron?+
Yes — polyphenols in tea and coffee can cut iron absorption by ~50% when consumed with a meal. Wait 1 hour after eating before your cup.
Related tools
References
- Hurrell R, Egli I. Iron bioavailability and dietary reference values. Am J Clin Nutr. 2010;91(5):1461S–1467S.
- National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press, 2005.
- U.S. Department of Agriculture, Agricultural Research Service. FoodData Central. USDA, 2024.
Educational estimates only, not medical advice. Individual needs vary — consult a physician or registered dietitian.