Iron Deficit Calculator (Ganzoni)

About this calculator

The Ganzoni formula estimates total body iron deficit in milligrams: deficit = weight(kg) × (target Hb − actual Hb, in g/dL) × 2.4 + iron stores (typically 500 mg for adults ≥35 kg, or 15 mg/kg for children and lighter adults). The factor 2.4 converts the haemoglobin gap into the iron mass needed to rebuild red-cell haemoglobin, and the added store term accounts for replenishing the body's iron reserves, not just the blood itself.

Haematologists, nephrologists managing dialysis patients, and gastroenterologists treating iron-deficiency anaemia from chronic blood loss use this calculation to size a course of intravenous iron replacement, since oral iron is often too slow or poorly tolerated for larger deficits. It is a calculation tool only — the resulting figure is meant to inform a clinician's decision, not to be interpreted as a treatment recommendation.