How Much Should I Weigh? – The Ultimate Ideal Weight Guide & Calculator
Devine • Robinson • Miller • Hamwi — with body frame adjustment
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Table of Contents
How Much Should I Weigh? – The Factors That Matter
How much should I weigh? is one of the most common health questions. The answer isn't a single number – it depends on your gender, age, height, and body frame size. Medical experts use several well‑established formulas to estimate a healthy weight range. In this guide we'll explore each one, show you how to use our interactive calculator, and discuss the limitations so you can interpret the results correctly.
Whether you're a man or a woman, your ideal body weight (IBW) is influenced by your skeletal structure. A person with a larger frame will naturally weigh more than someone with a small frame, even at the same height. That's why our tool lets you select a body frame size – small, medium, or large – and applies a ±10% adjustment to the baseline calculation.
Remember: these formulas are designed for adults (≥18 years). For children and teenagers, BMI percentiles are used instead (see below).
Formulas for Finding the Ideal Weight
Over the decades, several researchers have proposed equations to estimate IBW. All of them start with a base weight (in kg) and add a certain amount for every inch (or cm) above 5 feet (152.4 cm). The following summarizes the four formulas implemented in our calculator:
Hamwi (1964) – male base 48.0 kg, female base 45.5 kg, adding 2.7 kg per inch for males and 2.2 kg per inch for females.
Devine (1974) – male base 50.0 kg, female base 45.5 kg, adding 2.3 kg per inch for both sexes.
Robinson (1983) – male base 52.0 kg, female base 49.0 kg, with 1.9 kg/inch for males and 1.7 kg/inch for females.
Miller (1983) – male base 56.2 kg, female base 53.1 kg, adding 1.41 kg/inch for males and 1.36 kg/inch for females.
G. J. Hamwi Formula (1964)
The Hamwi formula, one of the oldest, is still widely used in clinical settings. For men, the calculation starts at 48 kg for the first 5 feet (152.4 cm) and adds 2.7 kg for each additional inch. For women, the base is 45.5 kg, adding 2.2 kg per inch above 5 feet.
Female: IBW = 45.5 kg + 2.2 kg × (height in inches – 60)
This formula tends to give slightly lower values compared to more modern equations, but it remains a useful reference point.
B. J. Devine Formula (1974)
The Devine formula was originally created for drug dosage calculations. For men, it uses a base of 50 kg plus 2.3 kg per inch over 5 feet. For women, the base is 45.5 kg with the same 2.3 kg increment.
Female: IBW = 45.5 kg + 2.3 kg × (height in inches – 60)
Because the per‑inch addition is identical for both sexes, the Devine formula often produces the most balanced average when combined with others.
J. D. Robinson Formula (1983)
Robinson refined earlier work to better reflect population data. Men: 52 kg base + 1.9 kg/inch. Women: 49 kg base + 1.7 kg/inch.
Female: IBW = 49 kg + 1.7 kg × (height in inches – 60)
The Robinson formula generally yields a slightly higher ideal weight than Hamwi, especially for taller individuals.
D. R. Miller Formula (1983)
Miller's formula uses the highest base weights and the smallest per‑inch increments. Men: 56.2 kg + 1.41 kg/inch. Women: 53.1 kg + 1.36 kg/inch.
Female: IBW = 53.1 kg + 1.36 kg × (height in inches – 60)
This formula results in a narrower range of ideal weights across different heights.
Healthy BMI Range – Adults & Children
Body Mass Index (BMI) is another tool to assess weight relative to height. For adults (≥18), a BMI between 18.5 and 24.9 is considered healthy. Our calculator displays your personal healthy weight range based on this BMI interval.
For children and teens, BMI is interpreted differently using age‑ and sex‑specific percentiles. The Centers for Disease Control and Prevention (CDC) provides growth charts that classify children as underweight (<5th percentile), healthy weight (5th–85th), overweight (85th–95th), or obese (≥95th).
CDC BMI Charts for Boys and Girls (Ages 2–20)
Below are simplified SVG charts based on the CDC BMI‑for‑age percentiles.
Boys: BMI‑for‑age percentiles (2–20 years)
Girls: BMI‑for‑age percentiles (2–20 years)
The charts illustrate how BMI normally decreases during early childhood (the "adiposity rebound" around age 5-6) and then rises again through adolescence. A child whose BMI falls between the 5th and 85th percentiles is generally considered to have a healthy weight.
Limitations of Our IBW Calculator
While the formulas provide a useful starting point, they have important limitations:
- Not for athletes: Muscle weighs more than fat, so very muscular individuals may be classified as "overweight" even though they are healthy.
- Body frame estimation: The ±10% adjustment is an approximation. True frame size is best measured by wrist circumference or elbow breadth.
- Age factor ignored: The formulas do not account for the natural changes in body composition that occur with aging.
- Ethnic differences: The equations were developed primarily on Caucasian populations and may not apply equally to all ethnic groups.
- Not a diagnostic tool: Always consult a healthcare provider for a personalized assessment.
Use the calculator as a guide, not a definitive answer. Your overall health, diet, physical activity, and medical history are far more important than a single number on the scale.
References
- Hamwi, G. J. (1964). Therapy: changing dietary concepts. Diabetes Mellitus: Diagnosis and Treatment, 1, 73‑78.
- Devine, B. J. (1974). Gentamicin therapy. Drug Intelligence & Clinical Pharmacy, 8(11), 650‑655.
- Robinson, J. D., et al. (1983). Determination of ideal body weight for drug dosage calculations. American Journal of Hospital Pharmacy, 40(6), 1016‑1019.
- Miller, D. R., et al. (1983). A simple method for the estimation of ideal body weight. Drug Intelligence & Clinical Pharmacy, 17(12), 928‑931.
- Centers for Disease Control and Prevention. (2022). About Child & Teen BMI.
- World Health Organization. (2021). BMI classification.