Ideal Weight Calculator
The Five Ideal Weight Formulas Explained
All four major ideal body weight (IBW) formulas were originally developed in the 1960s–1980s for clinical use — primarily to calculate medication dosing, anaesthesia, and ventilator tidal volume in hospital settings. None were designed as weight-loss targets. Understanding what they calculate and why they differ is important context for interpreting the results.
Devine Formula (1974)
The most widely used formula in clinical medicine, developed by Dr. B.J. Devine for drug dosing. It remains the basis for many pharmaceutical references and mechanical ventilation protocols today.
IBW = 50 kg + 2.3 kg × (height in inches − 60)Women:
IBW = 45.5 kg + 2.3 kg × (height in inches − 60)
Robinson Formula (1983)
A revision of the Devine formula, developed to better reflect observed population data. It uses slightly different base weights and per-inch increments.
IBW = 52 kg + 1.9 kg × (height in inches − 60)Women:
IBW = 49 kg + 1.7 kg × (height in inches − 60)
Miller Formula (1983)
Another 1983 revision, producing slightly lower estimates than both Devine and Robinson — particularly for taller individuals. Often cited in nutrition literature.
IBW = 56.2 kg + 1.41 kg × (height in inches − 60)Women:
IBW = 53.1 kg + 1.36 kg × (height in inches − 60)
Hamwi Formula (1964)
The oldest of the four, developed by Dr. G.J. Hamwi and widely used in clinical dietetics. It uses a slightly different structure — a base for 5 feet, then a fixed increment per inch above or below.
IBW = 48 kg + 2.7 kg × (height in inches − 60)Women:
IBW = 45.4 kg + 2.27 kg × (height in inches − 60)
BMI-Based Healthy Weight Range
Rather than a single target, the BMI-based approach gives a range corresponding to the WHO healthy BMI band (18.5–24.9 kg/m²). This is not a formula with a single output — it produces the weight range within which a person's BMI would be considered healthy for their height.
Weight = 18.5 × height² (in meters)Upper bound:
Weight = 24.9 × height² (in meters)
Why the formulas disagree. The four IBW formulas were developed from different population samples and for different clinical purposes. At average heights (165–175 cm), they typically agree within 3–5 kg. The disagreement grows at shorter and taller heights because the linear relationship between height and ideal weight breaks down at the extremes — a limitation acknowledged in the original papers. The average across all four gives a reasonable central estimate without over-relying on any single formula.
Formula Comparison at Common Heights
| Height | Devine (M/F) | Robinson (M/F) | Miller (M/F) | Hamwi (M/F) |
|---|---|---|---|---|
| 155 cm (5'1") | 52.3 / 47.8 | 53.8 / 50.7 | 58.1 / 55.0 | 50.7 / 47.7 |
| 160 cm (5'3") | 57.7 / 53.2 | 57.6 / 54.1 | 61.2 / 57.9 | 56.1 / 52.9 |
| 165 cm (5'5") | 63.0 / 58.5 | 61.4 / 57.5 | 64.2 / 60.6 | 61.5 / 58.0 |
| 170 cm (5'7") | 68.4 / 63.9 | 65.2 / 60.9 | 67.2 / 63.4 | 66.9 / 63.2 |
| 175 cm (5'9") | 73.7 / 69.2 | 69.0 / 64.3 | 70.3 / 66.2 | 72.3 / 68.3 |
| 180 cm (5'11") | 79.1 / 74.6 | 72.8 / 67.7 | 73.3 / 69.0 | 77.7 / 73.5 |
| 185 cm (6'1") | 84.4 / 79.9 | 76.6 / 71.1 | 76.4 / 71.7 | 83.1 / 78.6 |
All weights in kg. M = Male, F = Female.
Limitations of Ideal Weight Formulas
IBW formulas are useful clinical tools but have well-documented limitations that are important to understand before using them as personal weight targets.
A more useful framing: Rather than targeting a specific formula output, most clinicians recommend using the BMI-based healthy weight range (18.5–24.9) as the broad target, and within that range, focusing on waist circumference (below 94 cm for men, below 80 cm for women) and body composition markers — which are better predictors of cardiometabolic risk than weight alone.
Frequently Asked Questions
Which ideal weight formula is the most accurate?
No single formula is universally most accurate — each was developed from a different population sample and for a different clinical purpose. At average heights, all four agree within 3–5 kg. The Devine formula is most widely used in clinical medicine (particularly for drug dosing and mechanical ventilation), while the BMI-based range is most commonly used in public health contexts. For a personal health target, the BMI-based healthy weight range (18.5–24.9) is generally the most defensible because it is grounded in epidemiological outcome data rather than an arbitrary formula.
Is ideal body weight the same as a healthy weight?
Not exactly. The term "ideal body weight" originated in clinical pharmacology as a dosing correction tool — not as a statement about the weight at which a person is healthiest. A "healthy weight" in the public health sense refers to a weight associated with lower risk of chronic disease, usually defined by BMI 18.5–24.9. These concepts overlap but are not identical. For most people at average height, the IBW formulas produce values within the healthy BMI range, but the alignment weakens at shorter and taller heights.
What if my current weight is already below the ideal weight?
If your current weight falls below both the formula predictions and the healthy BMI lower bound (BMI less than 18.5), being underweight carries real health risks — including reduced bone density, immune suppression, nutritional deficiencies, and impaired wound healing. If this is the case, a conversation with a healthcare provider about healthy weight gain strategies — focused on increasing lean muscle mass through resistance training and adequate protein intake — is appropriate. Avoid interpreting IBW formula outputs as targets to stay below.
Do these formulas apply to children and teens?
No. All four IBW formulas were developed and validated in adults. For children and teenagers, weight assessment should use BMI-for-age percentiles on the CDC or WHO growth charts, which account for the fact that the relationship between height and weight changes significantly as children grow. This calculator is designed for adults aged 18 and above only.
Should I use my ideal weight as a diet goal?
IBW formula outputs are better used as a rough reference point than as a rigid diet target. If your current weight is significantly above the ideal weight range, a more useful goal is to focus on sustainable behavior changes — dietary quality, physical activity, sleep — rather than a specific number. Research on weight management consistently shows that a 5–10% reduction in body weight from an elevated starting point produces meaningful improvements in blood pressure, blood sugar, and lipid profiles — often before reaching any formula-defined ideal weight.
