# Iron Deficiency Calculator (Ganzoni Formula)

URL: https://speedycalculator.com/calculators/health/iron-deficiency/
Last updated: 2026-10-30

> The iron deficiency calculator estimates total body iron deficit with the Ganzoni formula from weight and current and target haemoglobin, plus iron stores – the figure used to plan intravenous iron dosing.

## Inputs

- Weight (kg, lb, st, g)
- Current haemoglobin (g/dL, g/L, mmol/L)
- Target haemoglobin (g/dL, g/L, mmol/L)

## Results

- Iron stores
- Total iron deficit

## 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)
```

## Explanation

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

FieldWhat to enterWeightUnits: kg, lb, st, gCurrent haemoglobinUnits: g/dL, g/L, mmol/LTarget haemoglobinUnits: 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)351,00452.51,256701,50887.51,7601052,0121402,516
*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.*

## 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.

## FAQ

**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.


## Sources

- [Ganzoni AM. Intravenous iron-dextran: therapeutic and experimental possibilities. Schweiz Med Wochenschr, 1970](https://pubmed.ncbi.nlm.nih.gov/5413918/)