Ideal Body Weight Calculator

The Ideal Body Weight Calculator estimates ideal body weight from your height and sex using four published clinical formulas, Devine, Robinson, Miller, and Hamwi, and places them next to the healthy weight range implied by a body mass index of 18.5 to 25.

How It Works

1. Select your sex. Each formula uses a different base weight and per-inch increment for men and women.
2. Enter your height in centimeters. The calculator converts it to inches and measures how far it sits above 5 feet (60 inches).
3. The four formulas run. Each one starts from its base weight for a 5-foot adult and adds a fixed number of kilograms for every inch over 5 feet.
4. Compare the spread. You get four separate estimates plus the BMI-based healthy range for your height, so you can see how much the methods disagree before treating any single number as a target.

Formula

Every formula has the same shape, with different constants:

$\text{IBW} = \text{Base weight} + (\text{Increment} \times \text{Inches over 5 feet})$

| Formula | Men | Women | | --- | --- | --- | | Devine | 50.0 kg + 2.3 kg per inch | 45.5 kg + 2.3 kg per inch | | Robinson | 52.0 kg + 1.9 kg per inch | 49.0 kg + 1.7 kg per inch | | Miller | 56.2 kg + 1.41 kg per inch | 53.1 kg + 1.36 kg per inch | | Hamwi | 48.0 kg + 2.7 kg per inch | 45.5 kg + 2.2 kg per inch |

For heights under 5 feet, the inches-over-5-feet term goes negative and the formulas scale down accordingly. The healthy range comes from inverting the BMI formula at the band edges:

$\text{Weight} = \text{BMI} \times \text{Height in metres}^2$

using BMI values of 18.5 and 25.

Input Parameters

| Input | Unit | Realistic range | Notes | | --- | --- | --- | --- | | Sex | Choice | Male or female | Selects the formula constants | | Height | Centimeters | 100 to 220 cm for most adults | Calculator accepts values above 50 and up to 300 cm |

Worked Example

For a woman who is 165 cm tall:

1. Convert height: 165 / 2.54 = 64.96 inches, which is 4.96 inches over 5 feet.
2. Devine: 45.5 + (2.3 x 4.96) = 56.9 kg.
3. Robinson: 49.0 + (1.7 x 4.96) = 57.4 kg.
4. Miller: 53.1 + (1.36 x 4.96) = 59.8 kg.
5. Hamwi: 45.5 + (2.2 x 4.96) = 56.4 kg.
6. Healthy BMI range: height in metres is 1.65, and 1.65 squared is 2.7225. Lower edge: 18.5 x 2.7225 = 50.4 kg. Upper edge: 25 x 2.7225 = 68.1 kg.

The four formulas cluster between 56.4 kg and 59.8 kg, a spread of about 3.4 kg, and all four sit comfortably inside the BMI healthy range of 50.4 kg to 68.1 kg.

Interpreting Your Results

The formulas were built for clinical convenience, mainly drug dosing and nutritional assessment, not for defining how a person should look. Devine usually lands mid-pack, Hamwi gives the steepest increase per inch so it tends to be highest for tall men and lowest for shorter women, and Miller rises slowest with height.

Agreement matters more than any single value. When all four estimates fall inside the BMI healthy range, as in the example, the methods broadly agree for that height. When they diverge or fall outside the range, that is a sign the height-based approach is a poor fit for the individual, for example for very tall, very short, muscular, or older adults.

Use the range, not a point. Aiming for the middle of the overlap between the formula cluster and the BMI band is more defensible than chasing one equation's output to the decimal.

Choosing the Right Tool

• Use this Ideal Body Weight Calculator when you want the four clinical formulas reported separately, exactly as published, alongside a BMI 18.5 to 25 healthy range.
• Use the Ideal Weight Calculator if you prefer a single blended figure: it runs the same four formulas but averages them, uses a BMI ceiling of 24.9, and applies the base weights unchanged for heights under 5 feet.
• Use the BMI Calculator to classify your current weight against the standard BMI categories.
• Use the Calorie Calculator when the next question is how much to eat, since it works from your actual weight, age, and activity level.

Limitations

These formulas use height and sex only. They ignore body composition, so a strength athlete and a sedentary person of the same height receive identical estimates. They were derived from mid-20th-century reference populations and are not validated as personal targets for adolescents, pregnancy, amputees, or people with conditions that change fluid or tissue mass. The BMI range has the same limits, since BMI cannot distinguish muscle from fat. None of this output is a diagnosis or a dosing input.

Questions

Why do the four formulas give different answers?

Each author fitted different base weights and per-inch increments from different reference data. Devine published in 1974 for medication dosing, Robinson and Miller revised the approach in 1983, and Hamwi's 1964 rule uses the steepest increment. The differences are real, which is why this calculator shows all four instead of hiding the disagreement.

Is ideal body weight the same as a healthy weight?

No. The formulas estimate a statistical reference weight for a height. The healthy range from BMI is wider and usually more useful for personal planning. Being inside one and outside the other is common and is not by itself a health finding.

What if I am shorter than 5 feet?

This calculator lets the per-inch term go negative, so the estimates scale down below the base weights. The sibling Ideal Weight Calculator instead holds the formulas at their 5-foot base values for shorter heights, which is one reason the two pages can differ for the same person.

Sources and Methodology

The four equations are the published Devine (1974), Robinson (1983), Miller (1983), and Hamwi (1964) formulas, implemented with their original kilogram constants and converted heights. The healthy range uses the World Health Organization adult BMI band of 18.5 to 24.9, applied here with an upper edge of 25. Discuss dosing, nutrition, pregnancy, and medical decisions with a qualified clinician rather than relying on any height-based estimate.