Ideal Weight Calculator

What is Ideal Body Weight?

Ideal Body Weight (IBW) is a statistical estimate of a healthy body weight based on height, gender, and frame size. It was originally introduced to determine appropriate pharmaceutical dosages, but it is now widely used in fitness and medical circles to establish baseline target weights.

It is important to remember that "ideal" weight is a mathematical estimate. It does not dictate what you should weigh, but provides a healthy benchmark derived from clinical data.

Why Are There Multiple Formulas?

Over the years, different researchers developed equations to estimate IBW based on mortality rates and pharmaceutical safety studies. The four classic formulas are:

1. The Hamwi Formula (1964)

Developed by Dr. J.R. Hamwi, this is the oldest and remains popular among clinical dietitians.

• Men: 106 lbs + 6 lbs per inch over 5 feet (60 inches)
• Women: 100 lbs + 5 lbs per inch over 5 feet (60 inches)

2. The Devine Formula (1974)

Created by Dr. Ben Devine, this is the medical standard for calculating drug clearance rates.

• Men: 50.0 kg + 2.3 kg per inch over 5 feet
• Women: 45.5 kg + 2.3 kg per inch over 5 feet

3. The Robinson Formula (1983)

Dr. A.S. Robinson updated Devine's formula to align better with modern medical datasets.

• Men: 52.0 kg + 1.9 kg per inch over 5 feet
• Women: 49.0 kg + 1.7 kg per inch over 5 feet

4. The Miller Formula (1983)

Developed by Dr. D.R. Miller, this formula yields slightly higher results for shorter heights and lower results for taller heights.

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

Formula Comparison

The following table compares the output for a height of 5 feet 9 inches (175 cm) by gender:

Formula	Men (175 cm)	Women (175 cm)
**Hamwi (1964)**	72.6 kg (160.0 lbs)	65.8 kg (145.0 lbs)
**Devine (1974)**	70.7 kg (155.9 lbs)	66.2 kg (145.9 lbs)
**Robinson (1983)**	69.1 kg (152.3 lbs)	64.3 kg (141.8 lbs)
**Miller (1983)**	68.9 kg (151.9 lbs)	65.3 kg (144.0 lbs)

Our calculator averages these four formulas to give you a recommended range that accounts for statistical variance.

Healthy BMI Weight Ranges

In addition to height-based equations, the World Health Organization (WHO) defines healthy weight ranges using Body Mass Index (BMI). BMI represents weight in kilograms divided by the square of height in meters:

• Normal Weight Range: BMI 18.5 – 24.9
• Overweight Range: BMI 25.0 – 29.9
• Underweight Range: BMI < 18.5

The BMI healthy weight range is much broader than any single formula, providing a flexible scale that accommodates differences in body composition and bone density.

Limitations of Ideal Weight Calculations

While useful, these formulas have clear limitations:

• Muscle Mass: Muscle is denser than fat. Bodybuilders and strength athletes will weigh significantly more than their "ideal" weight while maintaining very low body fat.
• Frame Size: The formulas assume a medium frame size and do not adjust for individuals with naturally narrow or broad skeletal frames.
• Age: The formulas do not adjust for age, though minor weight gain is common and often healthy in older populations.

Related Resources

Related Calculators

• BMI Calculator — Compare ideal weight with actual BMI.
• Body Fat Calculator — Calculate body fat percentage.

External Authority Resources

• Devine Formula for Ideal Body Weight on PubMed — Scientific paper presenting the Devine equation.
• CDC Healthy Weight Information — Public health assessment tools.

Sources & Citations

• Devine BJ. Gentamicin therapy. Drug Intell Clin Pharm. 1974;8:650-655.
• Robinson JD, et al. Determination of ideal body weight for drug dosage. Am J Hosp Pharm. 1983;40(6):1016-1019.
• Miller DR, et al. Clinical application of a new ideal body weight formula. Am J Hosp Pharm. 1983;40:1019-1022.
• World Health Organization. Physical status: the use and interpretation of anthropometry. WHO Technical Report Series. 1995.

Using Ideal Weight Alongside Other Metrics

Ideal weight is most useful when interpreted alongside complementary metrics rather than in isolation:

Body Fat Percentage provides information that ideal weight formulas cannot — the proportion of your weight that is fat vs. lean mass. A 75 kg person with 12% body fat has a very different health profile than a 75 kg person with 28% body fat, even if both match the same "ideal weight" for their height.

Use our free Body Fat Calculator to estimate your body fat percentage using the US Navy measurement method, and our BMI Calculator to assess your weight-to-height ratio using the WHO classification.

Waist-to-Height Ratio (WHtR) is an increasingly recognised metric that predicts cardiovascular and metabolic risk independently of total weight. The target: keep your waist circumference below half your height. This metric removes muscle mass from the equation and focuses on visceral (abdominal) fat, which is the most metabolically harmful type.

Total Daily Energy Expenditure (TDEE) connects your ideal weight goal to a practical calorie target. Once you know your target weight, our TDEE Calculator can estimate your energy needs at that weight and activity level — giving you the calorie deficit or surplus required to reach it.

Frame Size Adjustment

The four formulas (Hamwi, Devine, Robinson, Miller) all assume a medium skeletal frame. If you have a naturally small or large frame, adjust the ideal weight range:

• Small frame: Subtract 10% from the formula result
• Medium frame: Use the formula result directly
• Large frame: Add 10% to the formula result

Estimating frame size from wrist circumference:

Measure your wrist circumference with a tape measure at the narrowest point:

Men	Frame Size
Wrist < 6.5 inches	Small
Wrist 6.5–7.5 inches	Medium
Wrist > 7.5 inches	Large

Women (5'5" and under)	Frame Size
Wrist < 5.5 inches	Small
Wrist 5.5–5.75 inches	Medium
Wrist > 5.75 inches	Large

What to Do With Your Ideal Weight Result

Your ideal weight range is a benchmark, not a prescription. Here’s how to use it practically:

1. Set a realistic body weight goal within or near the range, adjusted for your frame size and activity level

2. Calculate your current deficit or surplus using our Calorie Calculator to find the daily intake needed to reach your target

3. Set a protein target at 1.6–2.2 g/kg of target body weight to preserve muscle during the journey — see our Protein Calculator

4. Track progress with body measurements alongside scale weight — waist, hip, chest, and arm measurements reveal body recomposition that the scale misses

Frequently Asked Questions

What is the most accurate ideal weight formula?

No single formula is definitively most accurate for all individuals — each was derived from different populations and purposes. Averaging the four formulas (as this calculator does) reduces reliance on any one model and provides a broader, more statistically robust estimate.

Can ideal weight be reached if I have high muscle mass?

Yes, but you may naturally exceed the formula estimates if you are highly muscular. This is not a health concern. Body fat percentage and waist-to-height ratio are more relevant indicators for muscular individuals than scale-based ideal weight formulas.

How long does it take to reach my ideal weight?

At a safe deficit of 250–500 kcal/day (0.25–0.5 kg/week), reaching an ideal weight that is 10 kg away takes approximately 5–10 months. Muscle-preserving strategies (resistance training, high protein) ensure that weight loss is predominantly fat rather than lean tissue.

Should children use ideal weight calculators?

No — adult ideal weight formulas do not apply to children and adolescents. For paediatric weight assessment, use CDC BMI-for-age percentile charts.

What if my current weight is already below the ideal range?

If your weight is below the recommended range, consult a healthcare provider. Underweight status is associated with bone density loss, immune suppression, hormonal disruption, and nutrient deficiencies. A supervised plan to increase muscle mass and improve overall body composition is appropriate.