Ideal Weight Calculator — Free Online Multi-Formula Tool

How to Use the Ideal Weight Calculator

1. Select your unit system: Choose Metric (kg/cm) or Imperial (lbs/ft). Results are displayed in your chosen unit.
2. Select your biological sex: Each formula uses different coefficients for males and females. Choose the sex that aligns with your biological body composition for the most relevant results.
3. Enter your height: Input your height accurately. All four formulas use height as the primary variable, so accuracy here directly affects result quality.
4. Enter your current weight: This allows the calculator to show how your current weight compares to the ideal weight average from all four formulas.
5. Review your results: The calculator displays the ideal weight from each of the four formulas, their average, your current weight, and the difference between your current weight and the average. Use the range across formulas as a target zone rather than focusing on any single number.

Ideal Weight Formulas

Step-by-Step Calculation Example

For a male who is 180 cm (5'11", or 71 inches) tall:

1. Inches over 60: 71 - 60 = 11 inches
2. Hamwi: 48.0 + (2.7 x 11) = 48.0 + 29.7 = 77.7 kg
3. Devine: 50.0 + (2.3 x 11) = 50.0 + 25.3 = 75.3 kg
4. Robinson: 52.0 + (1.9 x 11) = 52.0 + 20.9 = 72.9 kg
5. Miller: 56.2 + (1.41 x 11) = 56.2 + 15.5 = 71.7 kg
6. Average: (77.7 + 75.3 + 72.9 + 71.7) / 4 = 74.4 kg (164 lbs)

The four formulas suggest a range of 71.7 to 77.7 kg for a 5'11" male, with an average of 74.4 kg. The 6 kg spread between formulas reflects their different development methodologies.

Practical Examples

Example 1: Jason's Fitness Goal Setting

Jason is a 29-year-old male, 178 cm (5'10") tall, currently weighing 88 kg. He wants evidence-based weight goals:

• Hamwi: 48.0 + 2.7 x 10 = 75.0 kg
• Devine: 50.0 + 2.3 x 10 = 73.0 kg
• Robinson: 52.0 + 1.9 x 10 = 71.0 kg
• Miller: 56.2 + 1.41 x 10 = 70.3 kg
• Average: 72.3 kg | Difference: +15.7 kg

Jason is 15.7 kg above the average ideal weight. His trainer suggests targeting 78 kg initially (a realistic 10 kg loss) over 5-6 months, which would already produce significant health benefits, then reassessing whether to aim lower based on his body composition and how he feels.

Example 2: Claudia's Post-Surgery Recovery

Claudia is a 45-year-old female, 163 cm (5'4") tall, weighing 56 kg after weight loss surgery:

• Hamwi: 45.5 + 2.2 x 4 = 54.3 kg
• Devine: 45.5 + 2.3 x 4 = 54.7 kg
• Robinson: 49.0 + 1.7 x 4 = 55.8 kg
• Miller: 53.1 + 1.36 x 4 = 58.5 kg
• Average: 55.8 kg | Difference: +0.2 kg

Claudia is almost exactly at the formula average. Her medical team is pleased with her weight stabilization and focuses on ensuring she maintains adequate nutrition and muscle mass at this weight through balanced protein intake and light resistance exercise.

Example 3: Raj Comparing to His Athletic Build

Raj is a 34-year-old male competitive cyclist, 175 cm (5'9") tall, weighing 72 kg with visible muscularity:

• Hamwi: 48.0 + 2.7 x 9 = 72.3 kg
• Devine: 50.0 + 2.3 x 9 = 70.7 kg
• Robinson: 52.0 + 1.9 x 9 = 69.1 kg
• Miller: 56.2 + 1.41 x 9 = 68.9 kg
• Average: 70.3 kg | Difference: +1.7 kg

Raj is only 1.7 kg above the average, and his weight aligns closely with the Hamwi formula. Given his muscular build from cycling, this weight is appropriate. His sports dietitian notes that these formulas do not account for athletic body composition, and his low body fat percentage confirms he is at a healthy weight.

Ideal Weight Comparison Table

Tips and Complete Guide to Understanding Ideal Weight

Understanding the Context of These Formulas

These ideal weight formulas were developed in specific contexts that are important to understand. The Devine formula was created for calculating drug dosages, not for defining healthy body weight. The Hamwi formula emerged from insurance industry mortality data. Despite their origins, these formulas have been widely adopted in clinical practice because they provide simple, sex-specific weight estimates that correlate reasonably well with health outcomes. However, they should be viewed as rough guidelines, not precise prescriptions. Modern medicine increasingly recognizes that metabolic health markers (blood pressure, glucose, lipids) are more important than achieving a specific weight number.

Using the Average Wisely

The average of all four formulas is the most practical number to use because it smooths out the biases inherent in any single formula. However, the spread between the highest and lowest values (typically 5-10 kg for most heights) provides an equally important target range. If your current weight falls within this range, you are likely close to an appropriate weight for your height, assuming normal body composition. If you are significantly above or below the range, discussing your specific situation with a healthcare provider is recommended. Use the body fat calculator for additional perspective.

Beyond the Numbers

Ideal weight is influenced by far more than height and sex. Age, ethnicity, muscle mass, bone density, health conditions, and lifestyle all play significant roles. A person who exercises regularly and has significant muscle development may weigh more than these formulas suggest while being in excellent health. Conversely, a sedentary person at the "ideal" weight may have poor metabolic health due to low muscle mass and high body fat percentage. Focus on achieving and maintaining a weight that supports your energy, mobility, and clinical health markers rather than matching a formula precisely.

Common Mistakes to Avoid

• Treating any single formula as the definitive answer: No formula accounts for individual variation in body composition, frame size, or age. Use the range across formulas, not a single number.
• Ignoring body composition: Two people at the same weight and height can have very different health profiles depending on their muscle-to-fat ratio. Ideal weight formulas do not distinguish between muscle and fat.
• Using formulas for individuals under 5 feet tall: These formulas use 60 inches (5 feet) as a baseline. For shorter individuals, they may produce unreliable results.
• Setting unrealistic timelines: If you are significantly above the ideal range, targeting the average immediately is unrealistic. Aim for a 5-10% weight reduction first, which produces meaningful health benefits, then reassess.
• Comparing across formulas to find the most flattering result: The formulas serve different purposes and were derived from different populations. The average across all four provides the most balanced estimate.

Frequently Asked Questions