Ideal Weight Calculator

What is Ideal Body Weight?

Ideal body weight (IBW) is not a single number but a range based on your height and gender. Several formulas have been developed over decades to estimate a healthy target weight. These formulas serve as general guidelines — your actual ideal weight depends on body composition, muscle mass, and individual factors. Our calculator uses four scientifically recognized formulas and shows you the average and range, giving you a more complete picture than any single formula alone.

Ideal Weight Formulas

Robinson Formula (1983)

Miller Formula (1983)

Devine Formula (1974)

Hamwi Formula (1964)

All four formulas use height in inches relative to a baseline of 5 feet (60 inches). The calculator automatically converts your input from centimetres to inches using the factor 1 inch = 2.54 cm.

Step-by-Step Example

Interpreting Your Results

The range between the four formulas is typically 3-5 kg. Here's how to use these results wisely:

• Average: The most balanced estimate. Use this as your primary reference point.
• Lower end (Miller): More suitable for smaller-framed individuals.
• Upper end (Hamwi/Devine): More suitable for larger-framed or muscular individuals.
• Within 10% of average: If your current weight is within 10% of the average ideal weight, you are likely in a healthy range.

Real-Life Use Cases

• Setting weight goals: Use the ideal weight range as a realistic, evidence-based target rather than arbitrary numbers.
• Medical assessments: Doctors use IBW to calculate drug dosages, ventilator settings, and nutrition requirements.
• Fitness planning: Personal trainers use IBW alongside body fat percentage to design customized workout and nutrition programs.
• Insurance and health screening: Some life insurance providers use IBW formulas as part of their health risk assessment.

Limitations

These formulas were developed for adults of average build and don't account for muscle mass, bone density, ethnicity, or age. Athletes and very muscular individuals may have an "ideal weight" higher than these estimates. Use them as general guidelines, not strict targets.

Common Mistakes to Avoid

• Treating the Number as an Absolute: Ideal body weight is a range, not a single perfect number. Being a few kilograms outside the "ideal" does not automatically mean you are unhealthy.
• Ignoring Body Composition: If you carry a lot of muscle mass, your healthy weight will likely be higher than these formulas predict. These formulas don't know your muscle-to-fat ratio.
• Setting Unrealistic Goals: Using the lowest end of the formula range (like the Miller formula) when you naturally have a larger, broader frame can lead to unhealthy dieting behaviors.

Sources & Citations

• Robinson, J. D., et al. (1983): Determination of ideal body weight for drug dosage calculations.
• Miller, D. R., et al. (1983): Formulas for calculating ideal body weight.
• Devine, B. J. (1974): Gentamicin therapy. Drug Intelligence & Clinical Pharmacy.
• Hamwi, G. J. (1964): Therapy: changing dietary concepts.

Frequently Asked Questions

Which formula is the most accurate?

No single formula is universally best. The Robinson formula is commonly used in clinical settings. Using the average of all four formulas gives a reasonable range.

Why do the formulas give different results?

Each formula was developed using different population samples and methodologies. The differences reflect the natural variation in what constitutes a healthy weight.

Does ideal weight change with age?

These formulas don't account for age, but body composition does change with aging. Older adults may carry slightly more weight while still being healthy.