Ideal Body Weight Calculator

Calculation Method	Target Weight (US)	Target Weight (Metric)	Clinical Focus
Devine Equation	159.8 lbs	72.5 kg	Pharmacology, Clearance & ICU Dosing
Robinson Equation	157.0 lbs	71.2 kg	Empirical General Population Fit
Miller Equation	153.9 lbs	69.8 kg	Reduced Height Stature Bias
Hamwi Formula	166.0 lbs	75.3 kg	Endocrine & Diabetic Dietetics
WHO Healthy BMI (18.5-24.9)	128.9 – 173.5 lbs	58.5 – 78.7 kg	Global Morbidity & Mortality Risk Range

Calculation Method

Target Weight (US)

Target Weight (Metric)

Clinical Focus

Devine Equation

159.8 lbs

72.5 kg

Pharmacology, Clearance & ICU Dosing

Robinson Equation

157.0 lbs

71.2 kg

Empirical General Population Fit

Miller Equation

153.9 lbs

69.8 kg

Reduced Height Stature Bias

Hamwi Formula

166.0 lbs

75.3 kg

Endocrine & Diabetic Dietetics

WHO Healthy BMI (18.5-24.9)

128.9 – 173.5 lbs

58.5 – 78.7 kg

Global Morbidity & Mortality Risk Range

Ideal Body Weight (IBW): Clinical Pharmacology & Anthropometric Models

Ideal Body Weight (IBW) is a standardized medical benchmark originally developed in clinical pharmacology to compute therapeutic drug dosages for narrow therapeutic index medications (such as aminoglycosides, theophylline, and anaesthetic agents). In obese or severely underweight individuals, gross body mass fails to represent drug distribution volume accurately because adipose tissue has lower metabolic clearance and blood perfusion than lean tissue.

The Classical Anthropometric Formulations

Clinical algorithms model ideal body weight based on stature (height) relative to a 5-foot (60-inch / 152.4 cm) baseline. Letting $h_{\text{over5ft}} = \text{height (inches)} - 60$:

1. Devine Formula (1974) — Medical Gold Standard

Formulated by Dr. Ben J. Devine, this is the most universally adopted benchmark in pharmacokinetics:

\begin{aligned} \text{IBW}_{\text{male}} &= 50.0 \text{ kg} + 2.3 \text{ kg} \times h_{\text{over5ft}} \\ \text{IBW}_{\text{female}} &= 45.5 \text{ kg} + 2.3 \text{ kg} \times h_{\text{over5ft}} \end{aligned}

2. Robinson Formula (1983)

An empirical modification of Devine based on metropolitan life insurance actuarial studies:

\begin{aligned} \text{IBW}_{\text{male}} &= 52.0 \text{ kg} + 1.9 \text{ kg} \times h_{\text{over5ft}} \\ \text{IBW}_{\text{female}} &= 49.0 \text{ kg} + 1.7 \text{ kg} \times h_{\text{over5ft}} \end{aligned}

3. Miller Formula (1983)

Introduced to better align recommendations with athletic populations:

\begin{aligned} \text{IBW}_{\text{male}} &= 56.2 \text{ kg} + 1.41 \text{ kg} \times h_{\text{over5ft}} \\ \text{IBW}_{\text{female}} &= 53.1 \text{ kg} + 1.36 \text{ kg} \times h_{\text{over5ft}} \end{aligned}

4. Hamwi Formula (1964) — Clinical Nutrition Rule of Thumb

\begin{aligned} \text{IBW}_{\text{male}} &= 48.0 \text{ kg} + 2.7 \text{ kg} \times h_{\text{over5ft}} \quad (106 \text{ lbs} + 6 \text{ lbs/in}) \\ \text{IBW}_{\text{female}} &= 45.5 \text{ kg} + 2.2 \text{ kg} \times h_{\text{over5ft}} \quad (100 \text{ lbs} + 5 \text{ lbs/in}) \end{aligned}

World Health Organization (WHO) Healthy Weight Range

Because physiological body types vary across bone density and muscle mass, modern epidemiologists recommend an optimal weight target range derived from healthy Body Mass Index thresholds ($18.5 \le \text{BMI} \le 24.9\text{ kg/m}^2$):

W_{\text{min}} = 18.5 \times h_{\text{m}}^2, \quad W_{\text{max}} = 24.9 \times h_{\text{m}}^2

Step-by-Step Practical Calculation Example

Determine the ideal body weight for a female measuring 5 ft 7 in (170.2 cm):

Inches Above 5 Feet: $h = 67 - 60 = 7\text{ inches}$.
Devine Formula: $\text{IBW} = 45.5 + (2.3 \times 7) = 45.5 + 16.1 = \mathbf{61.6\text{ kg}} \, (135.8\text{ lbs})$.
Robinson Formula: $\text{IBW} = 49.0 + (1.7 \times 7) = 49.0 + 11.9 = \mathbf{60.9\text{ kg}} \, (134.3\text{ lbs})$.
Miller Formula: $\text{IBW} = 53.1 + (1.36 \times 7) = 53.1 + 9.52 = \mathbf{62.6\text{ kg}} \, (138.0\text{ lbs})$.
WHO Normal Weight Range ($h = 1.702\text{ m}$): $$\begin{aligned} W_{\text{min}} &= 18.5 \times (1.702)^2 = \mathbf{53.6\text{ kg}} \, (118.2\text{ lbs}) \\ W_{\text{max}} &= 24.9 \times (1.702)^2 = \mathbf{72.1\text{ kg}} \, (159.0\text{ lbs}) \end{aligned}$$

Scientific & Medical Formula Breakdown