Use the Dragon Iron Calculator to find out how much dietary iron a serving of your favorite food actually delivers. Pick a food from the list, enter a portion in grams or ounces, choose a daily target, and the tool instantly returns the iron in milligrams, the percentage of your daily goal covered, and the number of servings you would need to reach the full target.
Iron needs vary widely by age, sex, and life stage. A generic percentage bar on a package is often based on an average adult, which may not apply to you. This tool uses standard U.S. RDAs so you can compare your portion against a number that matches your situation. It is built for meal planners, students, athletes, and anyone trying to keep energy levels steady through smarter food choices.
Each result includes a simple step-by-step breakdown of the math, and an optional vitamin C tip helps you get more value from plant-based iron sources. Whether you are tracking anemia recovery, vegetarian nutrition, or sports performance, this tool makes iron intake easy to understand.
🧲 Dragon Iron Calculator
Estimate how much dietary iron a serving of food provides and compare it with your daily target.
How to Use This Tool
Start by selecting a food from the dropdown list — cooked spinach, beef liver, lentils, firm tofu, oysters, dark chocolate, and several other common iron sources are included. Next, enter the portion you actually eat. You can type the weight in grams or switch the unit to ounces; the calculator converts automatically at 1 oz = 28.3495 g. Then choose the daily iron target that matches your age, sex, and life stage from the provided RDA options.
Press Calculate iron and the result panel shows three numbers: the iron delivered by your serving in milligrams, the percentage of your daily goal that serving covers, and how many identical servings you would need to reach the full target. If you tick the optional vitamin C box, an absorption tip is appended to the result. A step-by-step breakdown of the arithmetic appears beneath the main values so you can verify the math by hand.
How the Calculation Works
Each food in the list has a reference iron value expressed in milligrams per 100 grams of edible portion, based on USDA nutrient composition data. The calculator converts your serving to grams (1 ounce = 28.3495 grams) and then applies a simple proportion:
Iron (mg) = iron per 100 g × serving weight (g) ÷ 100
The percentage of your daily target equals the iron in your serving divided by your selected RDA, multiplied by 100. The number of servings needed to reach the target is your target divided by the iron in one serving, rounded up to the next whole serving. This is the same logic used in nutrition labeling, just recalculated for your specific portion and personal target instead of a generic 2,000-calorie reference.
Reference: Daily Iron Targets
The daily targets come from the Recommended Dietary Allowances (RDAs) published by the National Institutes of Health for healthy individuals.
| Life stage | RDA (mg/day) |
|---|---|
| Adult men, 19–50 years | 8 mg |
| Adult women, 19–50 years | 18 mg |
| Pregnancy | 27 mg |
| Lactation | 9 mg |
| Boys, 14–18 years | 11 mg |
| Girls, 14–18 years | 15 mg |
Vegetarians and vegans need roughly 1.8 times the standard RDA because non-heme iron is absorbed less efficiently. Check with a healthcare provider if you have anemia, heavy menstrual bleeding, or any condition that changes iron needs.
Worked Examples
Example 1 — Cooked spinach: a 180 g cup of cooked spinach provides 3.6 mg of iron per 100 g. Iron = 3.6 × 180 ÷ 100 = 6.5 mg. Against an adult woman's 18 mg target, one cup covers 36% of her daily need, and she would need about 3 cups to reach the full target.
Example 2 — Beef steak: a 3 oz (85 g) cooked steak provides 2.6 mg per 100 g. Iron = 2.6 × 85 ÷ 100 = 2.2 mg. Against an adult man's 8 mg target, that steak covers 28%, and roughly 4 servings would meet the full target.
Tips for Better Iron Absorption
- Pair plant (non-heme) iron sources with vitamin C. Orange juice, strawberries, kiwi, bell peppers, and tomatoes all boost absorption when eaten in the same meal.
- Separate calcium-rich foods such as milk, cheese, and yogurt from iron-rich meals by a few hours, since calcium competes with iron for uptake.
- Tannins in tea and coffee bind iron and reduce absorption; wait about an hour after an iron-rich meal before drinking them.
- Cooking acidic foods like tomato sauce in a cast-iron skillet can add a small amount of iron to the dish.
Frequently Asked Questions
Why is the food list limited?
The tool keeps a short, hand-checkable list of the most common iron sources so the math stays transparent and easy to verify. For thousands of additional foods, search USDA FoodData Central using the link below.
What is the difference between heme and non-heme iron?
Heme iron comes from meat, poultry, and fish and is absorbed at roughly 15–35% efficiency. Non-heme iron from plants, eggs, and fortified foods absorbs at only about 2–20%. The values shown are total iron, so plant-based results may overstate what your body actually uses. Vitamin C and cooking methods can improve non-heme absorption considerably.
Can I rely on this tool if I am anemic?
No calculator replaces medical advice. Iron deficiency anemia is diagnosed with blood tests, and supplements should only be taken on the recommendation of a healthcare professional because iron overload is also dangerous. Use this tool as an educational aid for planning iron-rich meals.