What is the Ganzoni formula?

The Ganzoni formula estimates total body iron deficit as: Iron deficit (mg) = Weight (kg) x (Target Hb - Actual Hb) x 2.4 + Iron stores. The 2.4 factor converts hemoglobin to iron using the relationship between blood volume, hemoglobin concentration, and iron content per gram of hemoglobin.

What iron store value is used?

For patients weighing 35 kg or more, iron stores are set to 500 mg as per the standard Ganzoni formula. For patients under 35 kg (typically children), iron stores are calculated as 15 mg/kg body weight.

What target hemoglobin should I use?

The target hemoglobin depends on clinical context. Common targets are 12 g/dL for women and 13 g/dL for men, but your physician may set a different goal based on the patient's condition, comorbidities, and treatment guidelines.

Is this calculator suitable for pediatric patients?

The formula adjusts iron stores for patients under 35 kg using 15 mg/kg, making it applicable to pediatric patients. However, pediatric iron dosing should always be verified by a specialist.

How accurate is this formula?

The Ganzoni formula is a widely accepted estimation tool, but it can underestimate iron requirements in some patient populations such as those with chronic inflammation. Clinical judgment and follow-up laboratory monitoring remain essential.

Which IV iron products match the 200, 500 and 1,000 mg session columns?

Iron sucrose is usually given in doses of up to 200 mg, so read the 200 mg column. Ferric carboxymaltose and ferric derisomaltose allow larger single doses, commonly 500 to 1,000 mg, with weight-based caps that differ by product and country. A 70 kg patient going from Hb 8.5 to 15 g/dL needs 1,592 mg: 8 doses of 200 mg or 2 of 1,000 mg. Check the product label for the maximum dose and the gap between doses.

Can I use this to calculate oral iron dosing?

The Ganzoni formula is primarily used for intravenous (IV) iron replacement. Oral iron bioavailability varies widely, so IV iron dose calculations are not directly applicable to oral supplementation planning.

Iron Deficit Calculator

Calculate total iron deficit in milligrams using the Ganzoni formula from patient weight, actual Hb, and target Hb.

Patient Parameters

Body Weight

Actual Hemoglobin (g/dL)

Current measured hemoglobin level

Target Hemoglobin (g/dL)

Desired hemoglobin level after treatment

Enter patient data and click Calculate to see the iron deficit.

Total Iron Deficit

— mg

Ganzoni Formula Result

Low dose (< 500 mg) High dose (≥ 1,000 mg)

Formula Breakdown

Body Weight —

Hb Deficit (Target - Actual) —

Circulating Iron (Weight x Hb Deficit x 2.4) —

Iron Stores —

Total Iron Deficit —

Typical Infusion Guidance

200 mg/session

—

sessions

500 mg/session

—

sessions

1000 mg/session

—

sessions

Session counts rounded up. Actual dosing schedule depends on the specific iron preparation and clinical protocol.

This calculator is a clinical reference tool only. Always verify iron replacement dosing with a qualified healthcare professional before administration.

Summary

The Iron Deficit Calculator uses the Ganzoni formula to determine how many milligrams of iron a patient needs to correct iron-deficiency anemia. It accounts for body weight, the difference between actual and target hemoglobin, and an additional iron store replenishment component. This tool is intended as a clinical reference aid — always confirm dosing with a qualified healthcare provider.

How it works

Enter the patient body weight in kilograms.
Enter the actual (current) hemoglobin level in g/dL.
Enter the target hemoglobin level in g/dL.
The calculator applies the Ganzoni formula: Iron deficit (mg) = Weight (kg) x (Target Hb - Actual Hb) x 2.4 + Iron stores.
Iron stores are automatically set to 500 mg for patients weighing 35 kg or more, and 15 mg/kg for lighter patients.
Review the calculated total iron dose and per-session split guidance.

Use cases

Determine IV iron replacement dose for iron-deficiency anemia.
Pre-surgical anemia optimization to reduce transfusion risk.
Chronic kidney disease patients requiring iron supplementation.
Postpartum iron deficiency management.
Inflammatory bowel disease patients with iron malabsorption.
Oncology patients with treatment-related anemia.
Clinical pharmacists verifying iron infusion orders.
Medical students learning the Ganzoni formula.

Frequently Asked Questions

Last updated: 2026-05-28 · Reviewed by Nham Vu

Iron Deficit Calculator

Use the Iron Deficit Calculator

Patient Parameters

Typical Infusion Guidance

Summary

How it works

Use cases

Frequently Asked Questions