Most people don’t realize tea is a source of dietary iron — and also one of the common drinks that can reduce iron absorption. This Tea Iron Calculator estimates the amount of iron in a serving of brewed tea based on tea type, serving size, and brewing strength, so you can understand what your daily cup contributes to your iron intake.
Using approximate USDA reference values for brewed teas, the tool converts cups or milliliters into milligrams of iron, calculates the percentage of the Daily Value (18 mg), and estimates absorbable non-heme iron. It’s useful for nutrition students, dietitians, and anyone managing their iron levels.
Keep in mind that brewed tea contains much less iron than many plant foods, but its polyphenols can block absorption of iron from other foods eaten at the same time. This calculator is a planning guide, not a medical measurement.
🍵 Tea Iron Calculator
Estimate iron from a serving of brewed tea
How to Use This Tool
Select the tea type from the dropdown, enter your serving size in cups or milliliters, and choose a brewing strength. You can also tap a preset button to quickly enter 1 cup, 2 cups, or 500 mL. Press Calculate Iron to see the estimated iron content for that serving. The Reset button clears both the inputs and the result area so you can try another tea or portion.
The result panel shows four useful numbers:
- Iron per 100 mL after adjusting for brewing strength.
- Total iron in your serving in milligrams.
- Share of the Daily Value using 18 mg as the reference for adults.
- Estimated absorbable iron using a conservative 3% non-heme iron absorption rate.
If you know the exact iron label value for a specific tea product, you can treat it as the baseline and adjust the calculation mentally: multiply your volume in mL by that value, then divide by 100 and apply the strength factor.
How the Iron Estimate Is Calculated
Brewed tea contains only a small fraction of the iron found in dry tea leaves. Most of the iron in your mug comes from water-soluble minerals released during steeping, so the calculation starts with a baseline amount per 100 mL for each tea type.
Formula: Iron (mg) = volume (mL) × iron per 100 mL ÷ 100 × strength factor.
For example, a 240 mL cup of black tea with a baseline of 0.02 mg per 100 mL and a regular strength factor of 1.00 gives 240 × 0.02 ÷ 100 × 1.00 = 0.048 mg. The strength factor accounts for steeping time: 0.75 for a light or short steep, 1.00 for regular, and 1.35 for a strong or long steep. Values are based on typical entries in the USDA FoodData Central for brewed tea.
Iron in tea is non-heme iron, which has lower bioavailability than heme iron from animal foods. The human body typically absorbs only about 2–5% of non-heme iron, so this calculator uses 3% as a middle estimate. That means the absorbable-iron number is much smaller than the total iron number — and both are small compared with foods like lentils or spinach.
Why Tea Can Lower Your Iron Absorption
Beyond the small amount of iron tea itself provides, tea is well known for affecting how your body handles iron from other foods. Tea leaves contain polyphenols, including tannins, catechins, and gallic acid, which bind non-heme iron in the digestive tract and keep it from being absorbed efficiently.
Studies suggest that drinking tea with a meal can reduce non-heme iron absorption by a substantial margin, especially for plant-based iron sources. Black tea and green tea tend to have the strongest effect because they are made from the same Camellia sinensis leaves and contain high levels of tannins. Herbal infusions, such as chamomile, mint, or rooibos, are generally lower in tea tannins but can still contain polyphenols that influence iron absorption to some degree.
Tip: If you are trying to raise your iron levels, drink tea between meals rather than with iron-rich meals. Pairing plant iron with vitamin C sources like citrus, bell peppers, or strawberries can also improve absorption.
Reference Iron Values for Brewed Tea
The table below lists the approximate baseline values used by this calculator. They match the options in the tea type dropdown and are intended for planning and education, not as a replacement for laboratory analysis.
| Tea Type | Iron per 100 mL (mg) |
|---|---|
| Black tea | 0.02 |
| Green tea | 0.02 |
| Oolong tea | 0.015 |
| White tea | 0.01 |
| Herbal blend (chamomile, mint, rooibos) | 0.08 |
| Decaffeinated black tea | 0.02 |
These values are averages. A particular batch of leaves, a different steeping temperature, or a longer infusing time can shift the result noticeably.
Worked Examples
Example 1 — Regular black tea: A 240 mL cup (about 8 oz) of black tea at regular strength gives 240 × 0.02 ÷ 100 × 1.00 = 0.048 mg of iron, which is about 0.27% of the 18 mg Daily Value. At 3% absorption, the body might retain roughly 0.0014 mg.
Example 2 — Strong herbal blend: Two cups (480 mL) of a chamomile-mint blend steeped long, with a 0.08 mg/100 mL baseline and a 1.35 strength factor, gives 480 × 0.08 ÷ 100 × 1.35 = 0.518 mg, which is about 2.88% of the Daily Value. The absorbable estimate is about 0.016 mg.
These examples show why tea is rarely a meaningful dietary source of iron for most people. What matters more is how tea affects the iron you get from the rest of your meal.
Limitations and Notes on Accuracy
Actual iron in brewed tea can vary with leaf grade, tea bag versus loose leaf, water mineral content, brewing time, and whether you add milk, lemon, or sweetener. The values in this calculator are educational estimates, not lab results. If you drink tea with meals, the inhibiting effect on non-heme iron can be substantial even though the iron supplied by the tea itself is small.
If you brew with well water or mineral-rich tap water, the water itself can contribute additional iron beyond the tea leaves. For a separate estimate of that source, see the water iron calculator.
Important: This tool is not a medical diagnostic. Iron deficiency should be evaluated by a doctor with a ferritin or hemoglobin test, especially if you experience fatigue, pale skin, dizziness, or shortness of breath.