Ideal Weight Calculator

How Ideal Weight Is Calculated

“Ideal weight” is a simplified clinical tool used to estimate medication dosing, anesthesia requirements, and nutritional targets — not a judgment about attractiveness or health. Several formulas exist, each developed by different researchers.

Devine formula (most clinically used):

For males:

IBW (kg) = 50 + 2.3 × (Height in inches − 60)

For females:

IBW (kg) = 45.5 + 2.3 × (Height in inches − 60)

Worked example — 5'9" male (69 inches):

IBW = 50 + 2.3 × (69 − 60) = 50 + 2.3 × 9 = 50 + 20.7 = 70.7 kg (156 lb)

Robinson formula (1983 — slightly more accurate):

Males: IBW = 52 + 1.9 × (inches over 5 feet) Females: IBW = 49 + 1.7 × (inches over 5 feet)

Miller formula (1983):

Males: IBW = 56.2 + 1.41 × (inches over 5 feet) Females: IBW = 53.1 + 1.36 × (inches over 5 feet)

BMI-based ideal weight range:

Ideal weight range = BMI range (18.5–24.9) × Height (m)²

For someone 5'9" (1.753 m):

Low: 18.5 × 1.753² = 56.8 kg (125 lb) High: 24.9 × 1.753² = 76.5 kg (169 lb)

Important context:

These formulas were developed for average-framed, Caucasian adults. They are less accurate for:

• Athletes (underweight result due to high muscle mass)
• People under 5 feet tall (formula becomes negative for very short individuals)
• Elderly individuals (bone density loss shifts the ideal range)

Clinicians use ideal body weight primarily for drug dosing (chemotherapy, antibiotics) — not as a weight-loss target.