Ideal Weight Calculator
Estimate your ideal body weight based on height and gender using the Devine formula. Commonly used in clinical settings to guide medication dosing and nutrition planning.
About this calculator
The Devine formula, developed by Dr. B.J. Devine in 1974, estimates ideal body weight (IBW) in kilograms based on height in inches above 5 feet (60 inches). The formulas are: IBW (male) = 50 + 2.3 × (height_in − 60) and IBW (female) = 45.5 + 2.3 × (height_in − 60), where height_in = height in cm ÷ 2.54. The base values (50 kg for men, 45.5 kg for women) represent the estimated IBW at exactly 5 feet, and 2.3 kg is added for each additional inch of height. Originally designed for pharmacokinetic drug dosing, it is now widely used in nutrition, anesthesia, and respiratory care. Note that IBW is a guideline, not an absolute standard — body composition, frame size, and muscle mass are not accounted for.
How to use
Example: A 175 cm tall male. Step 1 — Convert height to inches: 175 ÷ 2.54 = 68.9 inches. Step 2 — Subtract 60: 68.9 − 60 = 8.9 inches above 5 feet. Step 3 — Apply formula: IBW = 50 + 2.3 × 8.9 = 50 + 20.47 = 70.5 kg. Result: The ideal body weight for a 175 cm male is approximately 70.5 kg (about 155 lbs). This value can serve as a reference for caloric needs, medication dosing, or setting a realistic weight-management goal.
Frequently asked questions
How accurate is the Devine formula for estimating ideal body weight?
The Devine formula provides a reasonable population-level estimate but was originally derived from a small, predominantly male clinical dataset, limiting its precision for all individuals. It does not account for body composition, bone density, ethnicity, or muscle mass — a highly muscular athlete may have an IBW well above the formula's estimate without any health risk. Research comparing IBW formulas consistently shows variability of ±10–15% versus measured healthy weights. It is best used as a rough clinical reference rather than a personal fitness target.
What is the difference between ideal body weight and healthy BMI weight range?
Ideal body weight (IBW) using the Devine formula yields a single number, while a healthy BMI range (18.5–24.9 kg/m²) produces a weight range spanning several kilograms. For a 175 cm male, the healthy BMI range is roughly 57–76 kg, while the Devine IBW is about 70.5 kg — which falls comfortably within that range but is not the same value. BMI-based healthy weight is generally preferred for public health use, while IBW is more common in clinical and pharmaceutical contexts such as ventilator tidal volume settings and chemotherapy dosing.
When is ideal body weight used in medical practice?
Clinicians use IBW most frequently when calculating weight-based medication doses, particularly for drugs that distribute poorly into fatty tissue, such as certain antibiotics, anticoagulants, and chemotherapy agents. Anesthesiologists and respiratory therapists use IBW to set mechanical ventilator tidal volumes because lung capacity correlates with height rather than actual body weight. It is also used in enteral and parenteral nutrition calculations to estimate protein and caloric needs. In these contexts, using actual body weight for obese patients could lead to dangerous overdosing.