Lentils are one of the most reliable plant-based sources of iron. A single cooked cup delivers roughly 6.6 mg — around a third of the 18 mg recommended daily amount for adult women and over 80% of the 8 mg men need. Because lentil iron is non-heme, how much your body actually absorbs depends on the meal you eat alongside them and your individual needs.
This calculator turns those facts into something practical. Enter your serving size in grams, ounces, or cups, choose the lentil form (cooked or dry) and variety, then set your daily iron target and a realistic absorption rate. You'll instantly see total iron, its percentage of your daily need, an estimate of absorbed iron, and how much more lentil you'd need to eat to reach 100%.
It's built for vegetarians and vegans, athletes, dietitians, and anyone tracking micronutrients — making iron budgeting simple, down to the last milligram.
Lentil Iron Calculator
Estimate the iron in your lentil portion — as a percentage of your daily target and as absorbed iron, based on your serving size and meal context.
⚙️ Lentil details
Why Lentil Iron Varies by Form
Dry lentils contain roughly 9 mg of iron per 100 g, but once boiled they absorb water and the same weight of cooked lentils delivers only about 3.3 mg per 100 g. This is one of the most common sources of confusion when tracking iron. The table below lists the typical iron values used by this calculator, based on average values from the USDA FoodData Central database.
| Lentil type | Cooked iron (mg / 100 g) | Dry iron (mg / 100 g) |
|---|---|---|
| Brown / green | 3.3 | 9.0 |
| Red / split | 3.5 | 9.0 |
| Black (beluga) | 2.8 | 9.0 |
When you enter a serving in cups, the calculator uses standard cup weights: about 198 g for cooked lentils and 192 g for dry lentils. Ounces are converted using 28.35 g per ounce. That is why the same numeric portion in grams can produce very different iron totals depending on whether you choose cooked or dry.
How the Calculation Works
The calculation follows three simple steps. First, your serving size is converted to grams. Second, that weight is multiplied by the iron density of the selected lentil form and variety. Third, the resulting iron is expressed as a percentage of your daily target, adjusted for your chosen absorption rate.
Iron (mg) = (Iron per 100 g × Serving weight in g) ÷ 100
% of daily need = (Iron ÷ Daily target) × 100
Absorbed iron (mg) = Iron × Absorption rate ÷ 100
Lentils needed for 100% target (g) = Daily target ÷ Iron per 100 g × 100
Iron per 100 g values are not modified by cooking method here because the calculator's cooked values already reflect boiled lentils. If you use canned lentils, expect slightly lower iron than fresh cooked because the canning brine dilutes nutrients somewhat.
Worked Examples
Example 1: 1 cup cooked brown lentils, adult female target (18 mg). The serving converts to 198 g. Iron = 3.3 × 198 ÷ 100 = 6.53 mg. This covers 6.53 ÷ 18 × 100 = 36% of the daily target. At 10% absorption, the body absorbs about 0.65 mg of iron. To hit 18 mg solely from lentils, you would need 18 ÷ 3.3 × 100 = 545 g of cooked lentils, about 2.75 cups.
Example 2: 100 g dry red lentils, adult male target (8 mg). Dry red lentils contain 9.0 mg iron per 100 g, so this portion provides 9.0 mg — already 113% of the 8 mg target. At 15% absorption due to vitamin C intake, absorbed iron is 1.35 mg. Interestingly, after cooking this 100 g dry portion becomes about 260 g of cooked lentils, but the total iron stays roughly the same.
Tips for Better Iron Absorption
Lentil iron is non-heme, which is less absorbable than the heme iron found in meat. The absorption rate selector lets you account for this. To improve your actual iron uptake, combine lentils with foods rich in vitamin C, such as bell peppers, tomatoes, citrus fruits, or broccoli. Cooking lentils with a splash of lemon juice or vinegar also helps lower phytate activity.
- Pair lentils with a vitamin C source at the same meal — this can roughly double absorption.
- Soak or sprout dry lentils before cooking to reduce phytic acid.
- Avoid drinking tea, coffee, or red wine within an hour of eating lentils — their tannins inhibit iron uptake.
- Use a cast-iron pan when simmering lentil dishes to add a small amount of food iron.
Frequently Asked Questions
Is lentil iron the same as meat iron?
No. Meat provides heme iron, which is absorbed at 15–35% regardless of what else is eaten. Lentils provide non-heme iron, absorbed at only 2–20% depending on your body's stores and the meal composition. That is why a vegetarian diet often needs higher total iron intakes.
Should I choose cooked or dry lentils for tracking?
Choose the form you actually weigh and eat. If you cook from dry and measure the dry portion before cooking, use the dry setting. If you are logging a prepared meal by volume, the cooked setting is more accurate. The calculator supports both so you can compare.
Can I rely on lentils alone to meet my iron needs?
It is possible but requires very large portions. For example, an adult woman would need about 545 g of cooked lentils per day to reach 18 mg before accounting for absorption. In practice, combine lentils with other iron-rich plants such as chickpeas, tofu, pumpkin seeds, and fortified cereals to reach your target without monotony.
Reference Data: Daily Iron Recommendations
The calculator includes five common daily targets. These reference values are based on the National Institutes of Health Office of Dietary Supplements recommendations for healthy individuals.
| Population | Recommended daily iron (mg) |
|---|---|
| Adult men (19–50) | 8 |
| Adult women (19–50) | 18 |
| Pregnant women | 27 |
| Breastfeeding women | 10 |
| Teen girls (14–18) | 15 |
| Teen boys (14–18) | 11 |
If your individual needs differ — for example, due to heavy menstrual bleeding, endurance training, or a diagnosed iron deficiency — use a custom target instead of the presets. The NIH Iron Fact Sheet provides more detail on iron requirements and sources.