Iron Deficit (Ganzoni) Calculator

About this calculator

The Ganzoni formula, published in 1970, calculates the total body iron deficit that needs to be replaced (typically via IV iron infusion) in patients with iron-deficiency anemia: Total iron deficit (mg) = weight (kg) × (target Hb − current Hb) (g/dL) × 2.4 + iron stores (mg), where the 2.4 factor converts the hemoglobin gap into the iron mass needed to close it, and iron stores are conventionally assumed to be 500 mg for adults over 35 kg (lower for smaller patients).

Hematologists and gastroenterologists use this formula to dose IV iron precisely for patients who can't tolerate or don't respond adequately to oral iron — chronic kidney disease, inflammatory bowel disease and heavy menstrual bleeding are common reasons — since giving too little iron leaves the anemia under-treated while overshooting risks iron overload, so the formula-driven dose matters more here than a rough estimate would in most other supplement dosing.

This calculator takes body weight, current hemoglobin and target hemoglobin and returns the total iron deficit in milligrams using the Ganzoni formula.