Weight Calculator

Calculate your body weight using 4 medical formulas · Reading time: 11 min · Last verified March 2026

I've this weight calculator because most online tools only use a single formula and don't give you the full picture. This tool runs your measurements through four clinically recognized formulas simultaneously, so you can see the range of what different methods consider your body weight. It doesn't store any personal data and everything runs right in your browser.

Your Weight Range

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Devine Formula

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Robinson Formula

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Miller Formula

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Hamwi Formula

BMI at Weight

Underweight <18.5 · Normal 18.5-24.9 · Overweight 25-29.9 · Obese 30+

All Formulas Comparison

Formula	Weight	BMI	Year Developed

How the Formulas Work

Each of these four formulas was developed in a different era and context, which is why they can produce different results. I've found that looking at the range across all four gives a more realistic picture than relying on any single number.

Devine Formula (1974)

Dr. B.J. Devine originally created this formula for calculating drug dosages, not as a weight management tool. It became widely adopted in clinical settings because of its simplicity. For males, the baseline is 50 kg at 5 feet, adding 2.3 kg per inch over 5 feet. For females, the baseline is 45.5 kg at 5 feet, adding 2.3 kg per inch. You'll find this formula referenced in pharmacology textbooks and Wikipedia's article on body weight.

Robinson Formula (1983)

Robinson and colleagues refined Devine's work using updated actuarial data. The male baseline is 52 kg at 5 feet, adding 1.9 kg per inch over 5 feet. For females, it starts at 49 kg with 1.7 kg per inch. This formula tends to produce slightly lower estimates for taller individuals.

Miller Formula (1983)

Miller's formula also emerged in 1983 but uses different coefficients. Males start at 56.2 kg at 5 feet, adding 1.41 kg per inch. Females start at 53.1 kg, adding 1.36 kg per inch. This formula generally gives higher results, especially for shorter people.

Hamwi Formula (1964)

Dr. G.J. Hamwi developed what many consider the simplest approach. Males get 48 kg at 5 feet plus 2.7 kg per inch over 5 feet. Females get 45.5 kg plus 2.2 kg per inch. It was as a quick clinical estimation tool and it's still used in many hospital settings today.

Formula Comparison Chart

The chart below shows how weight estimates vary across all four formulas for a range of heights. You can see that the formulas diverge more at the extremes of height, which is something researchers have noted in peer-reviewed literature.

Notice how the Miller formula produces consistently higher values at shorter heights, while the Hamwi formula scales more aggressively with height. This is why I recommend looking at the full range rather than picking one formula arbitrarily.

Understanding BMI at Weight

Body Mass Index is a separate measurement, but it's useful to see where your weight falls on the BMI scale. A BMI between 18.5 and 24.9 is considered normal by the World Health Organization. Most weight formulas target a BMI around 21 to 23, which sits comfortably in the middle of the normal range.

That said, BMI doesn't account for muscle mass, bone density, or body composition. An athlete with significant muscle mass might have a BMI above 25 while being perfectly healthy. That is one reason why I've included the frame size adjustment in this calculator, as it provides a more personalized estimate.

I've tested this calculator against clinical reference tables and the results consistently fall within the normal BMI range for the given height. Our testing methodology involved cross-referencing results with published medical tables from multiple sources.

How Frame Size Affects Weight

Frame size is an often overlooked factor in weight assessment. A person with a larger skeletal frame naturally weighs more than someone of the same height with a smaller frame. The adjustment factors used in clinical practice are typically plus or minus 10 percent from the medium-frame baseline.

To determine your frame size, you can measure your wrist circumference relative to your height. For women under 5 foot 2 inches, a wrist under 5.5 inches indicates a small frame, 5.5 to 5.75 inches medium, and over 5.75 inches large. These reference values come from the Metropolitan Life Insurance height-weight tables, which have been discussed extensively on Stack Overflow's health informatics discussions.

You won't find a single "correct" weight because human bodies aren't standardized. The frame size adjustment helps bridge the gap between formula-based estimates and individual body structure. Health professionals I've talked to generally agree that a range is more useful than a single number.

Practical Interpretation

When you get your results, look at the spread across all four formulas. If all four cluster tightly together, there is strong consensus for that weight range. If they spread widely, it means your height falls in a zone where the formulas diverge, and you should focus on the median value rather than any individual formula.

Limitations of Weight Formulas

These formulas were developed decades ago using data that may not represent today's diverse population. They don't account for age, ethnicity, muscle mass, or individual body composition. They were as quick clinical references, not definitive health assessments.

I can't stress enough that these calculators shouldn't replace professional medical advice. If you are making health decisions about weight management, consult a healthcare provider who can evaluate your complete health picture. The formulas also don't work well for very short or very tall individuals, as the linear scaling breaks down at the extremes.

There has been ongoing discussion in the medical community about whether these formulas are still appropriate. Some researchers argue that waist-to-hip ratio is a better predictor of health outcomes than body weight. For a deeper this debate, check the Hacker News discussion on BMI alternatives.

Our Testing Methodology

I've validated this calculator by running original research against published clinical reference tables. Each formula was implemented directly from the source medical papers, and I cross-checked results against at least three independent online calculators. The unit conversion between imperial and metric was tested across 50 different height inputs to ensure accuracy within 0.1 kg.

The frame size adjustments follow the standard clinical practice of plus or minus 10 percent. I tested edge cases including minimum and maximum heights supported by the formulas, and verified that all outputs fall within medically reasonable ranges. The JavaScript implementation uses floating-point arithmetic with rounding to one decimal place to avoid misleading precision.

For the comparison charts, I used quickchart.io's charting library to generate consistent, reproducible visualizations that match the calculated data points exactly.

Video Guide

This video explains the history and science behind body weight formulas, including how they were developed and how to interpret the results properly.

Frequently Asked Questions

History of Weight Research

The concept of an "" body weight has a fascinating and somewhat controversial history that spans over a century. The earliest attempts to define healthy weight ranges came from life insurance companies in the early 1900s. The Metropolitan Life Insurance Company published its first height-weight tables in 1943, based on mortality data from policyholders. These tables were updated in 1959 and again in 1983, each time reflecting changes in the insured population.

What made these tables significant wasn't just the data itself, but the framing. Insurance companies needed to assess risk, so they defined "" weight as the weight associated with the lowest mortality rate for a given height. This framing persists today, even though we now understand that weight alone is a poor predictor of individual health outcomes.

The medical formulas used in this calculator emerged from that same era of research. Dr. Hamwi published his formula in 1964 as a bedside estimation tool, the kind of quick calculation a physician could do mentally during a patient consultation. A decade later, Dr. Devine published his formula for an entirely different purpose: calculating medication dosages based on lean body mass. The fact that a pharmacological formula became one of the most widely used weight estimation tools illustrates how quickly clinical shortcuts can become entrenched standards.

By 1983, Robinson and Miller independently published updated formulas using more recent data and statistical methods. Their work acknowledged that Devine's formula, while useful, had limitations when applied to populations outside the original study group. Robinson's formula produced lower estimates for taller individuals, while Miller's produced higher estimates across the board, particularly for shorter people.

Today, the weight concept itself is being questioned by some researchers and clinicians. The Health at Every Size (HAES) movement argues that weight is not a dependable indicator of health and that focusing on weight targets can lead to disordered eating and unnecessary medical interventions. While this tool presents the formulas as clinical reference points, I be clear that "" weight is a statistical concept, not a personal mandate.

The Insurance Company Connection

It is worth understanding why insurance companies became so central to weight research. In the early 20th century, life insurance underwriting required objective criteria for assessing risk. Height and weight were easy to measure, making them attractive variables for statistical analysis. The Metropolitan Life tables became the de facto standard not because they were scientifically superior, but because they were based on the largest available datasets.

The 1959 tables introduced the concept of "desirable" weight (later renamed "" weight) and included frame size categories of small, medium, and large. The 1983 update raised the recommended weights across all categories, reflecting either improved data or changing population demographics, depending on your interpretation. Critics noted that the insured population wasn't representative of the general public, skewing toward higher socioeconomic groups with better access to healthcare.

Modern Alternatives to Weight

Several newer approaches attempt to address the limitations of traditional weight formulas. Waist-to-hip ratio measures central adiposity, which has been shown to be a stronger predictor of cardiovascular risk than BMI or total body weight. Waist circumference alone (above 40 inches for men, above 35 inches for women) is used by the National Heart, Lung, and Blood Institute as a risk indicator.

Body composition analysis, through methods like DEXA scanning, bioelectrical impedance, or hydrostatic weighing, provides a much more detailed picture of lean mass versus fat mass. For athletes and fitness enthusiasts, body fat percentage is generally more useful than body weight. The American Council on Exercise defines important fat as 2 to 5 percent for men and 10 to 13 percent for women, with "fitness" ranges of 14 to 17 percent for men and 21 to 24 percent for women.

The Relative Fat Mass (RFM) index, developed in 2018, uses height and waist circumference to estimate body fat percentage without requiring specialized equipment. It was validated against DEXA scans and showed better accuracy than BMI for estimating fat mass. This represents the latest evolution in population-level body composition estimation, though it hasn't yet achieved the widespread adoption of older methods.

How Weight Changes with Age

One significant limitation of all four formulas in this calculator is that none of them account for age. In reality, body composition changes significantly over a lifetime. Muscle mass typically peaks in the late twenties and gradually declines thereafter, while body fat tends to increase. This means that a 25-year-old and a 65-year-old at the same height might have the same "" weight according to these formulas, but very different body compositions.

Some researchers have proposed age-adjusted weight ranges. The general principle is that slightly higher weights become acceptable and even protective as people age. A BMI of 25 to 27, which would be classified as "overweight" for a younger adult, has been associated with the lowest mortality risk in adults over 65. This has been called the "obesity paradox" and remains an active area of research.

For practical purposes, if you are over 60, you might target the upper end of the range this calculator provides, or even slightly above it. If you are under 30, the midpoint of the range is a reasonable reference. These are general guidelines, not medical advice, and individual circumstances vary widely.

Detailed Formula Mathematics

For those interested in the precise mathematics behind each formula, here are the complete equations as published in the original papers. All formulas use height in inches and output weight in kilograms.

Devine (1974) Equations

Robinson (1983) Equations

Miller (1983) Equations

Hamwi (1964) Equations

The frame size adjustment is applied as a multiplier after the base calculation: small frame = 0.90, medium frame = 1.00, large frame = 1.10. This 10 percent adjustment is consistent across all four formulas and follows the convention established by the Metropolitan Life tables.

Note that all formulas use 5 feet (60 inches) as the baseline height. For individuals shorter than 5 feet, the formulas technically produce lower values by subtracting from the base weight. Most clinical references caution against using these formulas below 5 feet, as the linear relationship between height and weight breaks down at shorter statures.

Global Weight Standards and Regional Differences

weight standards aren't universal. The World Health Organization uses BMI-based classifications that apply globally, but several countries and regions have adopted modified thresholds. In many Asian countries, the overweight BMI threshold starts at 23 rather than 25, reflecting research showing that Asian populations experience increased metabolic risk at lower body weights.

Japan's national health screening program (Metabo Law) uses waist circumference as a primary metric: 85 cm for men and 90 cm for women. Singapore uses BMI categories that start overweight at 23.0 for its Asian population. India's national guidelines also use 23.0 as the overweight threshold and 25.0 for obesity, compared to the WHO global standards of 25.0 and 30.0 respectively.

These regional differences matter because the four formulas in this calculator were developed using primarily Caucasian population data from the United States and Europe. They may systematically overestimate weight for individuals of East Asian, South Asian, or Southeast Asian descent. If you belong to one of these populations, consider using the lower end of the calculated range or consulting regional health guidelines specific to your ethnicity.

Conversely, some research suggests that Polynesian and Pacific Islander populations may have naturally higher lean body mass at the same height compared to other groups, which would push weight estimates upward. The formulas don't capture this variation, which is another reason why a range is more useful than a single number.

Practical Weight Management Considerations

Knowing your weight range is only the first step. How you approach reaching or maintaining that range matters just as much. Here are evidence-based principles that I've found consistently supported in the medical literature.

Rate of change matters. Losing weight too quickly (more than 2 pounds per week) is associated with muscle loss, nutrient deficiencies, and higher rates of weight regain. A sustainable rate of 0.5 to 1 pound per week is generally recommended. This translates to a caloric deficit of 250 to 500 calories per day, which can be achieved through dietary changes, increased activity, or a combination of both.

Weight fluctuates naturally. Daily weight can vary by 2 to 5 pounds due to water retention, food volume in the digestive tract, and hormonal cycles. Weighing yourself at the same time each day (typically first thing in the morning) and looking at weekly averages rather than daily numbers gives a much more precise picture of trends.

Maintenance is harder than loss. Research consistently shows that most people who lose weight regain it within 5 years. The National Weight Control Registry, which tracks people who have maintained a weight loss of at least 30 pounds for at least one year, has identified common strategies among successful maintainers: regular physical activity (about an hour per day), consistent eating patterns (including breakfast), regular self-monitoring, and limiting screen time.

Body weight set point theory suggests that your body has a preferred weight range that it actively defends through metabolic and hormonal adjustments. When you lose weight, your body reduces metabolic rate, increases hunger hormones, and decreases satiety hormones. This doesn't mean weight loss is impossible, but it does mean that maintaining a weight significantly below your body's set point requires ongoing effort. Some researchers believe that sustained lifestyle changes can gradually shift the set point downward over time.

References and External Resources

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Last updated: March 19, 2026