Ideal Weight Calculator

"How much should I weigh?" is one of the most common health questions people ask. The answer is not a single number. Ideal body weight (IBW) is a target weight estimated from your height and biological sex using established medical formulas. These formulas were originally created to help physicians calculate drug dosages, ventilator settings, and nutritional requirements for hospitalized patients — they were never designed as aesthetic goals or fitness targets.

The concept of an "ideal" weight has a long history. Insurance companies in the early 20th century published "desirable weight" tables based on mortality data, most famously the Metropolitan Life Insurance tables of 1943 and 1983. These tables linked height, sex, and body frame size to the weight ranges associated with the lowest death rates among policyholders. While groundbreaking at the time, these tables had significant limitations: the sample was overwhelmingly white, middle-class Americans who could afford life insurance, and "frame size" was loosely defined.

Modern IBW formulas — Hamwi (1964), Devine (1974), Robinson (1983), and Miller (1983) — simplified the calculation to a linear equation based on height and sex alone. Each formula gives a slightly different result, which is why the WeightGPT ideal weight calculator runs all four side-by-side and also shows your healthy BMI range.

It is important to understand that IBW is a medical estimate, not a prescription. Your actual healthy weight depends on your body composition (the ratio of muscle, bone, water, and fat), your activity level, your age, your genetics, and many other factors. A bodybuilder and a sedentary person of the same height and sex may have vastly different ideal weights. Use the WeightGPT (Weight GPT) ideal weight calculator as a starting point, then use our free Body Fat Percentage Calculator, BMI Calculator, BMR Calculator, TDEE Calculator, and Macro Calculator for the full picture.

There are four major IBW formulas used in medicine and fitness. Each was developed independently and uses height and sex to estimate a target weight in kilograms. The WeightGPT ideal weight calculator computes all four instantly and shows the average.

The Hamwi formula is the oldest of the four and was published by Dr. G.J. Hamwi in 1964. It was originally used in clinical nutrition to estimate baseline caloric needs.

Example: A male who is 5'10" (10 inches over 5 feet): IBW = 48.0 + (2.7 × 10) = 75.0 kg (165.3 lb).

The Hamwi formula tends to give the lowest baseline for shorter men and a moderate estimate for women. It is still widely referenced in dietetics textbooks and clinical nutrition practice.

Dr. B.J. Devine published this formula in 1974 to standardize drug dosage calculations, particularly for gentamicin, an antibiotic. Over time it became the most commonly cited IBW formula in pharmacology and clinical medicine — and is the default IBW formula on most medical devices and in many electronic health record systems.

Example: A female who is 5'6" (6 inches over 5 feet): IBW = 45.5 + (2.3 × 6) = 59.3 kg (130.7 lb).

Note that the Devine formula uses the same coefficient (2.3 kg/inch) for both men and women — only the base weight differs. This makes it one of the simpler formulas, but also one that is less sensitive to sex-based differences in body composition at taller heights.

Dr. J.D. Robinson published a modified IBW formula in 1983 that aimed to better reflect the actual weights of healthy adults. It uses a lower coefficient per inch for women, producing a less steep weight increase as height grows.

Example: A male who is 6'0" (12 inches over 5 feet): IBW = 52 + (1.9 × 12) = 74.8 kg (164.9 lb).

The Robinson formula tends to produce more conservative (lower) estimates for tall individuals compared to the Hamwi or Devine formulas. Many nutrition professionals consider it one of the more realistic formulas for the general population.

Also published in 1983, the Miller formula was intended to correct what its author saw as an underestimation of ideal weight in taller adults. It starts with a higher baseline than any other formula.

Example: A female who is 5'4" (4 inches over 5 feet): IBW = 53.1 + (1.36 × 4) = 58.54 kg (129.1 lb).

The Miller formula is unique in that it produces the highest ideal weight for shorter individuals but the lowest rate of increase per inch. This means the four formulas tend to converge for people around 5'8"–5'10" and diverge significantly for very short or very tall people.

The table below compares all four formulas for common heights. All values are in kilograms (kg). The WeightGPT ideal weight calculator computes all four plus the average instantly.

As you can see, the formulas diverge significantly at the extremes of height. This is why WeightGPT shows all four results plus the healthy BMI range — giving you a realistic range rather than a single misleading number.

In addition to the four IBW formulas, the WeightGPT calculator also shows your ideal weight based on the healthy BMI range (18.5–24.9) defined by the World Health Organization. This method takes your height and calculates the weight range that would place you within a "normal" BMI:

Example: For someone 5'9" (1.753 m): Lower = 18.5 × 1.753² = 56.8 kg | Upper = 24.9 × 1.753² = 76.5 kg.

Many health professionals now prefer the healthy BMI range over any single IBW formula because it provides a range (typically spanning 15–25 kg or 35–55 lb) rather than a point estimate. This range accounts for natural variation in body composition, frame size, and muscle mass. For a deeper analysis, pair this with the WeightGPT BMI Calculator.

Ideal body weight formulas only use height and sex, but many other factors influence what a healthy weight actually is for you:

• Age: Older adults tend to accumulate more body fat and lose muscle mass (sarcopenia). A 60-year-old and a 25-year-old of the same height and sex may have very different ideal weights. Many clinicians allow a slightly higher weight target for older adults.
• Gender / Biological Sex: Males generally have more muscle mass and higher bone density, which is why most IBW formulas give men a higher ideal weight at the same height. Hormonal differences (testosterone vs. estrogen) also affect fat distribution.
• Height: All four IBW formulas are anchored to 5 feet (60 inches / 152.4 cm) and add weight per inch above that baseline. The formulas become less reliable at the extremes — under 5'0" or over 6'2".
• Body Frame Size: A person with a large skeletal frame will naturally weigh more than someone with a small frame at the same height. The Metropolitan Life Insurance tables from 1983 included frame size adjustments, and measuring your wrist circumference is a simple way to estimate your frame size (see the body frame size section below).
• Muscle Mass: Athletes and people who strength train may weigh significantly more than their IBW suggests while being very lean. Our Body Fat Percentage Calculator is a much better tool for these individuals.
• Ethnicity: Body composition norms vary across ethnic groups. For example, people of South Asian descent tend to carry more visceral fat at lower BMI values, while people of Polynesian descent tend to have higher muscle mass.
• Activity Level: A highly active person with significant lean mass may have a healthy weight well above their calculated IBW. Use the WeightGPT TDEE Calculator and Macro Calculator to match your nutrition to your activity.

Body frame size refers to the size of a person's skeletal structure. People with larger frames naturally weigh more due to heavier bones and a broader build. The simplest way to estimate your body frame size is by measuring your wrist circumference and comparing it to your height.

How to measure:

1. Wrap a flexible measuring tape around your dominant wrist, just below the wrist bone (the bony protuberance on the outside of your wrist).
2. Record the circumference in inches.
3. Compare to the tables below.

Women — Wrist Circumference & Frame Size

Men (height over 5'5") — Wrist Circumference & Frame Size

If you have a small frame, your ideal weight is likely at or below the IBW formula estimates. If you have a large frame, you can expect your ideal weight to be 10–15% above the formula estimates. The classic rule of thumb is: subtract 10% for a small frame, add 10% for a large frame.

The four IBW formulas (Hamwi, Devine, Robinson, Miller) were developed for adults and should not be used for children or adolescents. Children's bodies are constantly growing, and their body composition changes dramatically during puberty.

For children and teens aged 2–20, the CDC growth charts are the gold standard. These charts use age- and sex-specific BMI percentiles rather than fixed formulas:

A child's BMI is compared to other children of the same age and sex. For example, a 10-year-old boy at the 75th percentile weighs more than 75% of 10-year-old boys. As long as the percentile is between the 5th and 85th, the child is considered a healthy weight. Parents concerned about their child's weight should consult a pediatrician rather than using adult IBW calculators.

While IBW formulas are clinically useful, they have significant limitations that every user should understand:

• They ignore body composition. IBW formulas cannot distinguish between muscle and fat. A lean, muscular person and an unfit person of the same height and sex get the same IBW — which is clearly misleading for at least one of them.
• They only use height and sex. Age, frame size, ethnicity, fitness level, and medical history are all excluded. Two 5'8" men — one a 22-year-old athlete, the other a 70-year-old retiree — will get the same IBW.
• They were designed for populations, not individuals. IBW formulas are statistical averages derived from population-level data. They describe what the "average" healthy person of a given height and sex should weigh — not what you should weigh.
• They break down at extreme heights. All four formulas are anchored at 5 feet and become increasingly unreliable below 5'0" or above 6'2". For very short or very tall individuals, the healthy BMI range is usually a better guide.
• They don't account for ethnicity. The formulas were developed primarily using data from Caucasian populations. They may not apply equally to people of Asian, African, Hispanic, or Polynesian descent, who have different average body compositions.
• They can trigger unhealthy fixation. Focusing on a single "ideal" number can foster unhealthy relationships with weight, particularly for people prone to eating disorders. Health is a spectrum, not a point on a scale.

For all these reasons, WeightGPT shows all four formulas plus the healthy BMI range — encouraging you to think in terms of a range, not a single number. For a more complete assessment, use our Body Fat Percentage Calculator and BMI Calculator alongside this tool.

The very concept of "ideal weight" is a simplification. Health is not determined by a single number on a scale. Here are the key reasons why ideal weight should be treated as a rough guideline, not a definitive target:

• Body fat distribution matters more than total weight. Visceral fat (fat stored around internal organs) is far more dangerous than subcutaneous fat (fat stored under the skin). Two people at the same weight may have dramatically different health risk profiles based on where their fat is stored.
• Metabolic health is independent of weight. Research shows that metabolically healthy obese individuals (with normal blood pressure, blood sugar, and cholesterol) may have lower mortality risk than metabolically unhealthy normal-weight individuals.
• Fitness level is a stronger predictor of longevity than weight. Cardiorespiratory fitness (measured by VO2 max) has been shown to be a stronger predictor of all-cause mortality than BMI or weight.
• Weight fluctuates naturally. Your body weight can vary by 2–5 lbs (1–2.5 kg) within a single day due to hydration, food intake, sodium levels, and hormonal cycles.
• Mental health matters too. Obsessing over hitting an exact "ideal" number can lead to disordered eating, over-exercise, and anxiety. A healthy weight is one where you feel energetic, strong, and mentally well — not necessarily the number a formula produces.

The best approach is to use IBW as one data point among many. Combine it with your BMI, body fat percentage, waist-to-hip ratio, blood markers (cholesterol, blood sugar, blood pressure), and how you feel day-to-day. That holistic approach is exactly what WeightGPT (Weight GPT) was built to support.

All four IBW formulas produce different values for men and women at the same height. This reflects real physiological differences:

• Muscle mass: Men naturally carry more skeletal muscle than women (on average 36% vs. 28% of total body weight), which increases their ideal weight at the same height.
• Bone density: Male skeletons are typically denser and heavier, adding to the weight difference.
• Essential body fat: Women require a higher percentage of essential body fat (10–13%) compared to men (2–5%) for hormonal and reproductive health. While this fat is essential, it is lighter in total weight than the additional muscle men carry.
• Fat distribution: Women tend to store more fat in the hips, thighs, and breasts (gynoid pattern), while men tend to store fat around the abdomen (android pattern). Abdominal fat carries greater health risks.

The WeightGPT ideal weight calculator handles these differences automatically. Simply select your sex and enter your height — all four formulas adjust accordingly.

Knowing your ideal weight is the easy part. Actually reaching it is the challenge — and that is exactly what WeightGPT (Weight GPT) was built for. WeightGPT is the #1 AI weight loss and fitness app, used by over 10,000 people to transform their bodies.

Here is how WeightGPT goes beyond simple calculators:

• AI-Personalized Workout Plans: Enter your stats, goal, equipment access, and available training days — WeightGPT builds a complete, periodized workout program tailored to you.
• AI-Personalized Diet Plans: Get a custom meal plan matched to your TDEE, macro targets, dietary preferences (keto, vegan, halal, etc.), and food allergies.
• Progress Tracking: Log your weight, body measurements, and workouts. WeightGPT's AI adapts your plan as you progress.
• Complete Calculator Suite: All our calculators — BMI, Body Fat %, BMR, TDEE, Macros, and Ideal Weight — are available for free on the web and inside the app.

Numbers don't change bodies — plans do. Download WeightGPT free on Google Play and let the AI build your path to your ideal weight.