Spinach has a reputation as an iron powerhouse, but the amount you actually get depends on several factors: the form of spinach, how it was prepared, and how much you're eating. This calculator converts your serving size into milligrams of iron using standard USDA nutrition values for raw, boiled, frozen, and canned spinach. It also estimates the iron your body can realistically absorb, since the non-heme iron in spinach is absorbed less efficiently than the heme iron found in animal foods.
Use it to plan meals, track micronutrients, or check whether that big salad actually delivers a meaningful dose of iron. The tool reports total iron, the percent of the adult Daily Value, and an adjusted absorption estimate based on vitamin C co-factors and common absorption inhibitors.
This tool is designed for dietitians, fitness enthusiasts, people managing iron intake, and anyone curious about spinach nutrition. You can switch between grams, ounces, and cup measurements, choose the exact preparation method, and use quick presets for common portions.
🥬 Spinach Iron Calculator
Estimate iron in raw, boiled, frozen, or canned spinach.
Serving Size
Spinach Form
Absorption Factors (optional)
📊 Results
Based on USDA reference values. Absorption is an estimate only.
Step-by-Step Instructions
- Enter the amount of spinach you ate or plan to eat in the first input field.
- Choose the matching unit: grams, ounces, cups of raw chopped spinach, or cups of cooked spinach.
- Select the preparation form that best matches your food — raw, boiled, frozen cooked, or canned.
- Optionally check the absorption factors that apply to your meal.
- Press Calculate to see total iron, percent Daily Value, and estimated absorbed iron.
How the Iron Content Is Calculated
The calculator uses standard USDA nutrient values for iron in spinach per 100 g:
- Raw spinach: 2.71 mg iron per 100 g
- Boiled and drained spinach: 3.57 mg per 100 g
- Frozen spinach, cooked: 1.89 mg per 100 g
- Canned spinach, drained: 2.61 mg per 100 g
To find the total iron for your serving, the calculator converts your chosen unit into grams, then applies this simple formula: total iron (mg) = serving weight (g) × iron per 100 g ÷ 100. The Daily Value percentage is then calculated against 18 mg, the reference amount for iron used on nutrition labels for adults.
The values used here are based on the USDA FoodData Central database, the standard reference used by nutrition professionals. For raw spinach, 100 g is roughly a 3.5 oz portion. Because spinach shrinks dramatically when cooked, a 100 g portion of cooked spinach is much more compact and therefore contains more iron per forkful.
The absorption estimate is separate. Spinach contains non-heme iron, which the body absorbs at roughly 2–20% depending on the meal. The calculator starts with a conservative 5% baseline, adds about 10 percentage points when a vitamin C source is present, and subtracts about 3 percentage points when known inhibitors like tea, coffee, or dairy are included. This is a practical estimate, not a clinical measurement.
Iron Content Reference Table
These values give a quick comparison of common serving sizes:
| Spinach form | Iron per 100 g | Iron per 1 cup (approx.) |
|---|---|---|
| Raw, chopped | 2.71 mg | 0.81 mg (30 g) |
| Boiled, drained | 3.57 mg | 6.43 mg (180 g) |
| Frozen, cooked | 1.89 mg | 3.59 mg (190 g) |
| Canned, drained | 2.61 mg | 5.59 mg (214 g) |
Worked Examples
Example 1: Large raw salad. A 2-cup raw chopped spinach salad is about 60 g. Total iron = 60 × 2.71 ÷ 100 = 1.63 mg, which is 9% of the Daily Value. With a vitamin C-rich dressing or citrus on the side, estimated absorption would be higher.
Example 2: Cooked side dish. A 1-cup serving of boiled spinach weighs about 180 g. Total iron = 180 × 3.57 ÷ 100 = 6.43 mg, about 36% of the Daily Value.
Example 3: Canned spinach in a recipe. A 100 g portion of canned, drained spinach provides 2.61 mg, or about 15% of the Daily Value.
Factors That Affect Iron Absorption
The total iron figure is only part of the story. The non-heme iron in spinach is sensitive to what else is in your meal:
- Vitamin C from citrus, bell peppers, tomatoes, or strawberries can substantially improve non-heme iron absorption.
- Tea and coffee contain tannins that reduce absorption, so it is better not to drink them with an iron-rich meal.
- Calcium from milk, cheese, or yogurt can compete with iron absorption.
- Oxalates and phytates in spinach and whole grains further limit bioavailability.
If you are trying to improve iron status, pair spinach with vitamin C, avoid tea or coffee within an hour of meals, and consider cooking the spinach to help reduce oxalate content. If an absorption inhibitor is checked along with vitamin C, the benefit of vitamin C may partially offset the inhibitor, but the net effect is hard to predict exactly. The calculator models a moderate scenario rather than a best- or worst-case scenario.
Frequently Asked Questions
Is spinach the best plant source of iron? It is good, but not the most efficient. Other plant foods like lentils, beans, tofu, and fortified cereals often provide more iron per serving. Spinach's oxalates also limit absorption, which is why the absorption estimate in this calculator is lower than the total iron value.
Is cooked spinach higher in iron than raw spinach? By weight, yes. Because boiling removes water, 100 g of boiled spinach contains more iron than 100 g of raw spinach. But the iron content of the original leaves is unchanged — the serving simply becomes more concentrated.
Can spinach cause iron overload? Extremely unlikely from food alone. Non-heme iron absorption is tightly regulated, and spinach's own inhibitors limit uptake. Iron overload from diet alone is rare; it is more often associated with supplements or genetic conditions.
Should I use total iron or absorbed iron for meal planning? For general nutrition tracking, total iron is useful for comparing foods. For people with low iron stores, the absorbed amount is more meaningful. The absorption estimate here should be used as a guide, not a medical recommendation. If you are managing anemia or iron deficiency, speak with a healthcare professional.