How to use the iron intake calculator
Prepare the values for this calculation
Look up the NIH iron RDA or AI for an age/sex/life-stage group and compare it with an entered daily iron intake. Use the formula below to check that it answers your question. Read the input units before transferring figures from a statement, measurement or dataset.
Enter and check each input
- Age group: choose Birth to 6 months, 7–12 months, 1–3 years, 4–8 years, 9–13 years, 14–18 years, 19–30 years, 31–50 years or another listed option. Match this selection to the data you enter.
- Sex used by the reference table: choose Male, Female. Match this selection to the data you enter.
- Life stage: choose Not pregnant or lactating, Pregnant, Lactating. Match this selection to the data you enter.
- Estimated current intake (mg/day): enter a value at least 0. Use the unit named in the label or selected above. Do not leave this required field blank.
The input table gives a complete example. Keep units and time periods consistent across related fields.
Calculate and resolve any input error
Choose Calculate after entering the values. Changes also update the answer after a short pause. If an error appears, follow its message, correct the field and calculate again. Reset restores the example values.
Interpret the answer
Check Iron reference intake first. With the unchanged example inputs, it is 18 mg/day. Compare the additional metrics with the primary result; each has its own label and unit.
Compare and keep a useful result
The result diagram shows the inputs, method and output. A numeric chart is shown only when the calculation supports a meaningful numeric relationship.
Use Copy result or Download CSV to keep the answer. Share tool shares the page address without placing your input values in the URL. Recheck inputs and assumptions before using the result for a decision.
Iron Intake Calculator formula
Reference intake is selected from the NIH ODS iron Dietary Reference Intake table. Difference = entered daily intake − reference intake.
Inputs and units
| Input | Format / range | Example |
|---|---|---|
| Age group | Select an option | 19–30 years |
| Sex used by the reference table | Select an option | Female |
| Life stage | Select an option | Not pregnant or lactating |
| Estimated current intake (mg/day) | minimum 0 | 12 |
Worked example
Using the example inputs above, the iron reference intake is 18 mg/day.
- Iron reference intake
- 18 mg/day
- Reference type
- RDA
- Reference-table group
- 19–30 years; female; Not pregnant/lactating
- Entered intake
- 12 mg/day
- Difference from reference
- 6 mg/day below the reference
Results and assumptions
Iron reference value from the linked NIH Office of Dietary Supplements table. RDA means Recommended Dietary Allowance. This comparison is not a diagnosis and does not set a supplement dose or upper limit.
Sources and method references
Fix an input or unexpected result
Estimated current intake (mg/day) is required. Enter estimated current intake (mg/day) using the format and bounds in the input table. Zero and an empty field are different: use zero only if it is allowed and represents your data.
If your answer differs from the example, choose Reset and compare every field, including selected units and options. Check percentage versus decimal entry and whether values describe the same period. Round only the final displayed answer when reproducing the formula.
If a discrepancy remains, report the calculator issue with the page address, non-sensitive example inputs, actual result, expected result and a reference for your calculation.