Ideal Body Weight Calculator — IBW Calculator for Female and Male Free

Ideal Body Weight Calculator — Find Your IBW Using 5 Medical Formulas

Our free Ideal Body Weight Calculator calculates your IBW using five established medical formulas simultaneously — Hamwi, Devine, Robinson, Miller, and Peterson. Instead of giving you a single number that may not reflect your body type, the calculator shows all five results so you can see the range and understand how different formulas approach ideal weight calculation.

Enter your height, gender, and optional current weight to get your ideal body weight in kilograms or pounds, a comparison of all five formulas, your healthy weight range based on BMI, and how your current weight compares to the ideal if you enter it.

What Is Ideal Body Weight (IBW)?

Ideal body weight is a target weight range for a given height, calculated using medical formulas developed for clinical use. IBW formulas were originally created to estimate healthy weight ranges for medical purposes — primarily drug dosing calculations — and have since been widely used in nutrition, fitness, and general health planning.

IBW is different from BMI-based healthy weight. BMI gives you a range based purely on the ratio of weight to height squared. IBW formulas use height and gender to calculate a specific target weight, often with a range of plus or minus 10% representing the acceptable variation.

The key point about IBW is that no single formula is universally correct. Different formulas were developed for different purposes and populations, which is why our calculator shows all five side by side.

The 5 IBW Formulas Explained

Our calculator uses all five of the most established IBW formulas in medical and nutritional science.

The Hamwi formula, developed in 1964, is the most widely used in clinical nutrition settings. For men it assigns 48 kg for the first 5 feet of height and adds 2.7 kg for every additional inch. For women it assigns 45.5 kg for the first 5 feet and adds 2.2 kg per additional inch.

The Devine formula, developed in 1974, was originally created for estimating creatinine clearance in drug dosing research. For men it assigns 50 kg for 5 feet and adds 2.3 kg per inch. For women it assigns 45.5 kg for 5 feet and adds 2.3 kg per inch. The Devine formula is still widely used in pharmacology for medication dosing.

The Robinson formula, developed in 1983, was based on population averages from the 1959 and 1983 Metropolitan Life Insurance height and weight tables. For men it assigns 52 kg for 5 feet and adds 1.9 kg per inch. For women it assigns 49 kg for 5 feet and adds 1.7 kg per inch.

The Miller formula, developed in 1983, tends to produce the lowest IBW estimates and is most appropriate for slender or athletic body types. For men it assigns 56.2 kg for 5 feet and adds 1.41 kg per inch. For women it assigns 53.1 kg for 5 feet and adds 1.36 kg per inch.

The Peterson formula, developed in 2016, is the most recently developed IBW formula and uses a BMI-derived approach. It calculates IBW as the weight that would give a BMI of 22 for men and 21 for women at the given height. This formula is considered the most evidence-based of the five as it is derived from current BMI research.

IBW Calculator for Females — Key Differences

The IBW calculation for females differs from males in two ways. First, the base weight assigned for the first 5 feet of height is lower for women than for men across all formulas. Second, the weight added per additional inch of height is also slightly lower for women.

These differences reflect the population-level differences in body composition between men and women. Men on average have higher bone density, greater muscle mass, and lower body fat percentage than women at equivalent heights. The IBW formulas account for this by setting lower baseline weights for women.

For women specifically, the Hamwi formula remains the most widely used in clinical nutrition settings. The Peterson formula, which targets a BMI of 21 for women (versus 22 for men), reflects the slightly lower average healthy BMI associated with female body composition.

How to Calculate IBW for Female Manually — Step by Step

Using the Hamwi formula as an example:

Step 1: Convert your height to feet and inches. If you are 165 cm, divide by 2.54 to get 64.96 inches, which is 5 feet and approximately 5 inches.

Step 2: Calculate the inches over 5 feet. At 5 feet 5 inches, you have 5 extra inches.

Step 3: Apply the Hamwi female formula: 45.5 kg plus (2.2 kg multiplied by 5 extra inches) equals 45.5 plus 11.0 equals 56.5 kg.

Step 4: If you want the result in pounds, multiply by 2.20462: 56.5 multiplied by 2.20462 equals approximately 124.6 lbs.

The acceptable IBW range is typically the calculated result plus or minus 10%. For this example, the acceptable range would be 50.9 to 62.2 kg.

Actual Body Weight vs Ideal Body Weight

Actual body weight (ABW) is simply your current weight. Ideal body weight (IBW) is your calculated target. The relationship between these two values is used in clinical settings for several purposes.

When a patient is at or near their IBW, clinical calculations use actual body weight directly. When a patient is significantly above their IBW (typically more than 30% above), an adjusted body weight (AdjBW) is used for certain clinical calculations to better represent lean mass. The adjusted body weight formula is AdjBW equals IBW plus 0.4 multiplied by (ABW minus IBW).

Our calculator shows you the difference between your actual and ideal body weight when you enter your current weight, making it easy to understand how close you are to your IBW target.

Predicted Body Weight Calculator — For Clinical Use

Predicted body weight (PBW) is a specific IBW calculation used primarily in mechanical ventilation settings in critical care medicine. The PBW formula is used to determine appropriate tidal volumes for ventilated patients.

The PBW formula is nearly identical to the Devine formula: for men PBW equals 50 plus 2.3 multiplied by (height in inches minus 60); for women PBW equals 45.5 plus 2.3 multiplied by (height in inches minus 60). Our calculator’s Devine formula result serves as the predicted body weight calculation.

IBW vs BMI — What Is the Difference?

Both IBW and BMI are tools for assessing whether weight is appropriate for height, but they work differently.

BMI is a ratio of weight to height squared. It gives you a numerical score that falls into one of four categories: underweight, normal weight, overweight, or obese. BMI does not give you a target weight — it tells you where your current weight falls.

IBW gives you a target weight for your height using formulas that were developed for specific clinical purposes. It is more prescriptive than BMI. The healthy weight range generated by our calculator using BMI (18.5 to 24.9) is broader than individual IBW formula results because BMI captures a wider range of healthy weights.

For most practical purposes, aiming for a weight within the BMI healthy range of 18.5 to 24.9 and within 10% of your IBW formula average is a reasonable, evidence-based weight goal.

Frequently Asked Questions About IBW Calculator

What is the IBW calculator?

An IBW calculator calculates your ideal body weight using established medical formulas based on your height and gender. Our calculator uses all five main formulas simultaneously and shows you the average and individual results.

How do I calculate IBW for females?

Use the Hamwi formula for females: start with 45.5 kg for 5 feet of height and add 2.2 kg for every additional inch. Convert your height to feet and inches first, then apply the formula. Use our calculator above for instant results across all five formulas.

What is a normal IBW?

A normal IBW is simply the result of the IBW formula for your height and gender. The acceptable range is typically the calculated IBW plus or minus 10%. The five major formulas generally produce results within 5 to 10 kg of each other for most heights.

Which IBW formula is most accurate?

No single formula is universally most accurate — each was developed for a specific purpose and population. The Peterson formula is the most recently developed and is based on current BMI research. The Hamwi formula is most widely used clinically. Our calculator shows all five so you can use the average as your target range.

What is the Hamwi IBW calculator?

The Hamwi formula is one of five IBW formulas used in our calculator. For females it calculates IBW as 45.5 kg plus 2.2 kg per inch over 5 feet. For males it calculates IBW as 48 kg plus 2.7 kg per inch over 5 feet. It is the most commonly used formula in clinical nutrition settings.

What is predicted body weight?

Predicted body weight (PBW) is an IBW calculation used in critical care medicine to determine appropriate ventilator tidal volumes. It uses the Devine formula. Our calculator’s Devine result serves as the predicted body weight calculation.

Is ideal body weight the same as healthy weight?

IBW and healthy weight are related but not identical. IBW formulas give a specific target weight, while the BMI-based healthy weight range (18.5 to 24.9) gives a broader range. Most people with a weight within 10% of their IBW will also fall within the BMI healthy range.

Can I use the IBW calculator in pounds?

Yes. Select “Pounds (lbs)” from the result unit dropdown before clicking Calculate. All five formula results will be shown in pounds.

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