⚖️ Clinical Nutrition Tool

Ideal Body Weight Calculator

Calculate IBW using three clinically validated formulas (Hamwi, Devine, Robinson) plus Adjusted Body Weight for individuals with obesity. Essential for clinical dietetics and medication dosing.

Calculate Your Ideal Body Weight

Enter your height and gender to get IBW estimates from three clinical formulas.

Height (cm)

Biological Sex

Actual Weight (kg) (optional, for ABW)

IBW estimates across three clinical formulas:

Hamwi

—

Devine ⭐
—
kg (most used in RD practice)

Robinson

—

What Is Ideal Body Weight?

Ideal Body Weight (IBW) is a clinically derived estimate of a person's optimal body weight based on their height and sex. While not a perfect measure of health, IBW is widely used in clinical dietetics for calculating medication doses (including chemotherapy), estimating nutritional needs in critically ill patients, ventilator settings, and determining Adjusted Body Weight (ABW).

The Three Most Used IBW Formulas

1. Hamwi Formula (1964)

Women: 45.5 kg + 2.2 kg per inch over 5 feet
Men: 48.0 kg + 2.7 kg per inch over 5 feet

2. Devine Formula (1974) — Most Used in Clinical Practice

Women: 45.5 kg + 2.3 kg per inch over 5 feet
Men: 50.0 kg + 2.3 kg per inch over 5 feet

3. Robinson Formula (1983)

Women: 49.0 kg + 1.7 kg per inch over 5 feet
Men: 52.0 kg + 1.9 kg per inch over 5 feet

Adjusted Body Weight (ABW)

When a patient's actual weight exceeds their IBW by more than 30%, the Adjusted Body Weight is used for many clinical calculations:

ABW = IBW + 0.4 × (Actual Body Weight − IBW)

ABW accounts for the fact that some excess body weight is metabolically active tissue, and is used to calculate nutritional needs, drug dosing, and ventilator parameters in patients with obesity.

Clinical Uses of IBW

Medication dosing — many drugs (e.g., aminoglycosides, chemotherapy) are dosed based on IBW or ABW
Ventilator settings — tidal volumes in mechanical ventilation are based on predicted body weight (similar to IBW)
Nutritional needs estimation — used in clinical dietetics when actual weight is not appropriate (e.g., severe obesity, edema)
Dialysis calculations — used for dry weight targets and adequacy measures

Limitations of IBW

IBW formulas were derived from insurance actuarial data decades ago and were not designed to define "ideal" health weight for individuals. They do not account for:

Age (muscle mass changes throughout life)
Body frame size (small, medium, large)
Ethnicity-specific differences in body composition
Athletic or muscular builds

IBW should be used as a clinical tool, not as a personal weight goal. Work with a Registered Dietitian to determine appropriate weight targets for your individual health situation.

This tool is for informational and educational purposes only. Always consult a qualified clinician for medical decisions.