What Is Ideal Body Weight?
Ideal Body Weight (IBW) refers to a weight range that is associated with lower health risks for a given height and gender. Several formulas have been developed over the decades, each with slightly different assumptions. The most common are Devine (1974, originally for medical dosing), Robinson (1983, a refinement), Miller (1985, for nutrition settings), and Hamwi (1964, a traditional rule of thumb). None of these formulas account for muscle mass, body fat distribution, or bone density — use them as rough reference points, not absolute targets.
How to Use This Calculator
- Select your gender — Formulas differ for men and women.
- Choose your unit system — Metric (cm) or Imperial (ft/in).
- Enter your height — Click "Calculate" to see results from all four formulas plus the healthy BMI range.
Ideal Weight Formulas Explained
Devine Formula (1974)
Developed for calculating medication dosages. Men: 50 kg + 2.3 kg per inch over 5 ft. Women: 45.5 kg + 2.3 kg per inch over 5 ft. Despite its medical origins, it became the most widely used IBW formula in clinical practice.
Robinson Formula (1983)
A revision of Devine intended to be more accurate for the general population. Men: 52 kg + 1.9 kg per inch over 5 ft. Women: 49 kg + 1.7 kg per inch over 5 ft. Tends to give slightly lower values than Devine for taller individuals.
Miller Formula (1985)
Developed for nutrition assessment settings. Men: 56.2 kg + 1.41 kg per inch over 5 ft. Women: 53.1 kg + 1.36 kg per inch over 5 ft. More conservative for very tall individuals.
Hamwi Formula (1964)
The simplest and oldest formula, originally a rule of thumb. Men: 48 kg + 2.7 kg per inch over 5 ft. Women: 45.5 kg + 2.2 kg per inch over 5 ft. Tends to give higher values, especially for taller people.
Limitations of Ideal Weight Formulas
- Do not account for muscle mass — A muscular athlete may be "over" their IBW but have a healthy body fat percentage.
- Do not account for bone density — People with larger frames naturally weigh more at the same height.
- Based on limited populations — Original formulas were derived from relatively small sample sizes and may not apply to all ethnic groups.
- Age is ignored — Ideal weight does not change with age in these formulas, though body composition changes significantly.
Beyond Ideal Weight: Better Health Metrics
Body composition — Measured via DEXA, calipers, or bioelectrical impedance. Healthy body fat: 10-20% (men), 20-30% (women).
Waist circumference — A better predictor of health risk than weight alone. Target: under 40 in (102 cm) for men, under 35 in (88 cm) for women.
Waist-to-hip ratio — Target: under 0.90 (men), under 0.85 (women).
Physical fitness markers — Blood pressure, resting heart rate, strength, and endurance are better health indicators than weight on a scale.
Frequently Asked Questions
What is the ideal weight for my height?
There is no single number. For a 5'9" (175 cm) man, the range from all four formulas is roughly 67-78 kg (148-171 lbs). For a 5'4" (163 cm) woman: 54-64 kg (120-140 lbs). Use the healthy BMI range as a complementary reference.
Which formula is most accurate?
The Devine formula is the most widely used in medical settings. The Robinson formula is a common alternative that gives more conservative numbers. No formula is perfect — consider the range from all formulas plus your BMI.
Does ideal weight change with age?
These formulas do not account for age. However, after age 30, muscle mass typically decreases by 3-8% per decade, while body fat tends to increase. A slightly higher weight at older ages may be healthy — some studies suggest a BMI of 24-27 is optimal for adults 65+.
Sources: Devine BJ (1974), Robinson JD et al. (1983), Miller DR et al. (1985), Hamwi GJ (1964). National Institutes of Health (NIH).