Ideal Weight Calculator: Comparing Four Clinical Formulas

Ideal body weight (IBW) formulas have been used for decades in clinical settings to estimate a healthy weight for a given height. While no formula can account for individual differences in muscle mass, bone density, and body composition, these equations provide useful reference points for medication dosing, nutritional assessment, and general health benchmarking. Use our Ideal Weight Calculatorto see your results across all four major formulas.

The Four Major Formulas

Devine Formula (1974)

The Devine formula was originally developed to estimate creatinine clearance for drug dosing, but it became the most widely cited ideal weight formula in medical literature.

• Men: 50 kg + 2.3 kg per inch over 5 feet
• Women: 45.5 kg + 2.3 kg per inch over 5 feet

Robinson Formula (1983)

The Robinson formula was developed as a revision to Devine, using a larger sample and different statistical methods. It gives slightly lower weights than Devine for taller individuals.

• Men: 52 kg + 1.9 kg per inch over 5 feet
• Women: 49 kg + 1.7 kg per inch over 5 feet

Miller Formula (1983)

The Miller formula was derived from life insurance actuarial data and tends to give the lowest weight estimates among the four formulas, especially for tall individuals.

• Men: 56.2 kg + 1.41 kg per inch over 5 feet
• Women: 53.1 kg + 1.36 kg per inch over 5 feet

Hamwi Formula (1964)

The Hamwi formula is the oldest of the four and was developed for dietary consultation. It gives more aggressive weight targets with higher per-inch increments.

• Men: 48 kg + 2.7 kg per inch over 5 feet
• Women: 45.5 kg + 2.2 kg per inch over 5 feet

How Ideal Weight Differs From Healthy Weight

It is important to understand the distinction between "ideal weight" (a specific number from a formula) and "healthy weight" (the full BMI range of 18.5-24.9):

• Ideal weight is a single target number from a formula — useful as a reference but does not account for individual variation.
• Healthy weight range (18.5-24.9 BMI) is a broader zone that accommodates different body types, muscle masses, and frame sizes.

For most people, any weight within the healthy BMI range is a reasonable goal. The ideal weight formulas tend to fall in the middle to lower end of this range.

Sample Calculation

Let us calculate the ideal weight for a 5'9" (175 cm) male:

• Devine: 50 + 2.3 × 9 = 70.7 kg (156 lbs)
• Robinson: 52 + 1.9 × 9 = 69.1 kg (152 lbs)
• Miller: 56.2 + 1.41 × 9 = 68.9 kg (152 lbs)
• Hamwi: 48 + 2.7 × 9 = 72.3 kg (159 lbs)

The average across all four formulas is approximately 70.3 kg (155 lbs). The healthy BMI range for this height is approximately 57-76 kg (125-168 lbs).

Limitations of Ideal Weight Formulas

These formulas have several important limitations to keep in mind:

• No muscle mass adjustment: A muscular person may exceed these weights while having very low body fat.
• Body frame size: None of the formulas account for small, medium, or large bone structure.
• Ethnicity: The formulas were developed from predominantly Caucasian populations and may not be appropriate for all ethnic groups.
• Age: Body composition changes with age, but these formulas do not adjust for it.
• Single number: Health depends on many factors beyond weight, including body fat percentage, fitness level, diet quality, and metabolic health.

Using the Healthy BMI Range

The Body Mass Index (BMI) range of 18.5-24.9 is the most commonly used healthy weight guideline from health organizations worldwide. For any given height, you can calculate the corresponding weight range:

Healthy weight minimum: 18.5 × height(m)²
Healthy weight maximum: 24.9 × height(m)²

While BMI does not directly measure body fat, it correlates reasonably well with body fat percentage at the population level and provides a useful screening tool.

Setting Realistic Weight Goals

Here is a practical approach to setting weight goals:

1. Calculate your healthy BMI range — this is your broad target zone.
2. Check the ideal weight formulas — see where you fall relative to the average.
3. Consider your body composition — if you have significant muscle mass, you may be healthy above the formula targets.
4. Set a trend, not a target — focus on gradual progress (0.5-1 kg per week) rather than a specific number.
5. Look beyond the scale — track how your clothes fit, your energy levels, and your strength in the gym.

FAQs

Q: Which formula should I use?
A: For general reference, take the average across all four formulas. The Devine formula is most commonly used clinically, while the healthy BMI range provides the most comprehensive guide.

Q: Can I be healthy even if I weigh more than these formulas suggest?
A: Absolutely. If you have high muscle mass from regular strength training, you may weigh more than these formulas predict while having excellent health markers. Body fat percentage and waist circumference are better health indicators than weight alone.

Q: Why is there no height minimum in these formulas?
A: The formulas assume a base height of 5 feet (60 inches). For anyone shorter than 5 feet, the formula simply gives the base weight. This is a limitation — ideal weight formulas are less reliable for very short or very tall individuals.

Q: Do these formulas work for teenagers?
A: No. These adult formulas are not appropriate for growing children and teenagers. Pediatric growth charts and BMI percentiles should be used instead.

Q: How do I know if my current weight is healthy?
A: Check whether your weight falls within the healthy BMI range for your height. Also consider your waist circumference (under 40 inches for men, 35 inches for women) and lifestyle factors like diet quality, physical activity, and blood markers.