Ganzoni’s formula (1970) estimates the iron needed to rebuild haemoglobin and refill stores. It is used to calculate total-dose intravenous iron; doses are split according to the product’s maximum single dose.
How to use the Iron Deficiency Calculator
- Weight
- Current haemoglobin
- Target haemoglobin
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter weight, current haemoglobin and the target (often 15 g/dL, or 13 g/dL for lighter patients).
Inputs explained
| Field | What to enter |
|---|---|
| Weight | Units: kg, lb, st, g |
| Current haemoglobin | Units: g/dL, g/L, mmol/L |
| Target haemoglobin | Units: g/dL, g/L, mmol/L |
Example values
How the main result changes when Weight changes and everything else stays at the example values above:
| Weight (kg) | Total iron deficit (mg) |
|---|---|
| 35 | 1,004 |
| 52.5 | 1,256 |
| 70 | 1,508 |
| 87.5 | 1,760 |
| 105 | 2,012 |
| 140 | 2,516 |
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
Iron deficit (mg) = weight (kg) × (target Hb − actual Hb) (g/dL) × 2.4 + iron stores
Iron stores = 500 mg (≥ 35 kg) or 15 mg/kg (< 35 kg)
Worked example
Inputs — Weight: 70 kg; Current haemoglobin: 9 g/dL; Target haemoglobin: 15 g/dL.
Results — Iron stores = 500 mg; Total iron deficit = 1,508 mg.
Key terms
- Iron deficit
- Amount of iron needed to correct anaemia and refill stores.
Frequently asked questions
Is the Ganzoni formula used for oral iron?
Mainly for intravenous iron dosing.
Why add iron stores?
To refill the body's reserve after haemoglobin recovers.
How long until haemoglobin improves?
It typically rises about 1–2 g/dL within 2–4 weeks of treatment.