This free watercress iron calculator shows exactly how much iron you get from any serving of raw watercress. Enter a portion in grams, ounces, or chopped cups, and the tool instantly returns the iron in milligrams plus the contribution toward a daily target you can customize.
Watercress is a low-calorie leafy green with a surprisingly rich nutrient profile: 100 g of raw watercress provides about 0.2 mg of iron, along with vitamin C, vitamin K, folate, and calcium. Because vitamin C improves the absorption of non-heme iron, adding watercress to meals can be a smart move for plant-based eaters and anyone monitoring their iron intake.
Use this calculator for meal planning, daily micronutrient tracking, diet check-ins, or quick portion comparisons. It is designed for students, home cooks, dietitians, and anyone who wants a clearer picture of iron in a watercress-heavy diet.
🌿 Amount of Watercress
🎯 Daily Iron Target
How It Works
The calculator applies the USDA nutrient value for raw watercress: 0.20 mg of iron per 100 grams. It first converts your portion into grams using the selected unit, then multiplies by 0.20 ÷ 100 to get iron in milligrams, and finally expresses that result as a percentage of your daily iron target.
The conversion factors used are: 1 ounce = 28.3495 g, and 1 metric cup of chopped raw watercress = 34 g. If you enter the portion in grams, no conversion is needed. For example, a 150 g portion yields 150 × 0.20 ÷ 100 = 0.30 mg of iron. The step-by-step breakdown in the result panel walks through each stage so you can check the math yourself.
Non-heme iron: Watercress iron is non-heme iron, the plant form that the body absorbs less efficiently than the heme iron found in meat. Eating watercress together with vitamin C-rich foods such as citrus, tomatoes, kiwifruit, or bell peppers can improve absorption. For more on iron needs and absorption, see the NIH Iron Fact Sheet.
Worked Examples
Example 1 — 100 g serving: 100 g × 0.20 ÷ 100 = 0.20 mg of iron. Against an 18 mg daily target for adult women, that is 0.20 ÷ 18 × 100 ≈ 1.1% of the day's needs.
Example 2 — 1 chopped cup: 1 cup ≈ 34 g, so iron = 34 × 0.20 ÷ 100 = 0.068 mg, which rounds to about 0.07 mg. Against an 8 mg target for adult men, that is roughly 0.9%.
Example 3 — 2 oz portion: 2 oz = 56.7 g, so iron = 56.7 × 0.20 ÷ 100 = 0.113 mg, about 0.11 mg.
Notice that even generous salad portions contribute only a small fraction of daily iron needs. That is normal for leafy greens — they are valued for volume, variety, vitamin C, vitamin K, and fiber as much as for their iron content alone.
Iron Reference Table
| Portion | Approx. weight | Iron |
|---|---|---|
| 1 cup chopped | 34 g | 0.07 mg |
| 1 oz | 28.35 g | 0.06 mg |
| 50 g | 50 g | 0.10 mg |
| 100 g | 100 g | 0.20 mg |
| 150 g | 150 g | 0.30 mg |
| 250 g | 250 g | 0.50 mg |
Tips & Best Practices
- Weigh watercress with a kitchen scale for the most reliable numbers; volume measures of chopped leaves vary with packing density.
- A typical salad handful is about 40 g of raw leaves, while 100 g is a very generous bowl.
- Keep cooking methods gentle: a quick blanch or sauté preserves more vitamin C than prolonged boiling, and vitamin C helps your body absorb non-heme iron.
- Iron needs vary widely by life stage: adult men need about 8 mg/day, premenopausal women about 18 mg/day, and pregnant women about 27 mg/day.
Quick tip: To turn a modest watercress salad into a more iron-friendly meal, add grilled chicken or legumes plus a squeeze of lemon. The vitamin C boosts absorption of the non-heme iron from both the greens and the legumes.
Factors Affecting Accuracy
The 0.20 mg per 100 g figure comes from USDA FoodData Central and represents an average of analyzed samples. Real watercress iron content varies with variety, season, soil, and maturity, so treat the output as an estimate rather than a laboratory value.
- Chopped cup weights can range from about 30 to 40 g depending on how tightly the leaves are packed.
- Iron content of different batches can vary by roughly 15–20% around the published average.
- Very small amounts may display as 0.000 mg due to rounding at the third decimal place; this does not mean the food contains zero iron.
Frequently Asked Questions
Is watercress a good source of iron? Watercress contains a modest amount of iron — about 0.2 mg per 100 g — which is roughly 1% of the 18 mg daily target for adult women. It is not a concentrated iron source like liver, clams, or fortified cereals, but its vitamins A and C, vitamin K, and low calorie count make it a worthwhile addition to a varied diet.
Can I use watercress to treat iron deficiency? No. Diagnosed iron deficiency needs professional medical care, and iron supplements or prescribed treatment should not be replaced with greens. Watercress can support a balanced diet but will not correct a deficiency on its own.
Why do nutrition databases disagree on iron content? Growing conditions, harvest timing, leaf maturity, and laboratory methods all influence measured values. USDA FoodData Central lists raw watercress near 0.2 mg per 100 g, while some international databases report slightly different numbers. The USDA FoodData Central database is a reliable public reference for checking official values.