Ideal Weight Calculator
Use this free ideal weight calculator to find a sensible weight target for your height. The tool runs four classic ideal weight formulas at once (Hamwi, Devine, Robinson, and Miller) and shows the WHO BMI healthy range alongside them. Comparing all five numbers gives a much more honest picture than any single figure and helps you pick a goal that is realistic and actually healthy.
| Formula | Year | kg | lb |
|---|---|---|---|
| Hamwi | 1964 | 66.7 kg | 147.1 lb |
| Devine | 1974 | 65.9 kg | 145.4 lb |
| Robinson | 1983 | 65.2 kg | 143.7 lb |
| Miller | 1983 | 66.0 kg | 145.4 lb |
| BMI healthy range | 18.5 - 24.9 | 53.5 - 72.0 kg | 117.9 - 158.6 lb |
The four formulas were built decades ago for clinical purposes such as drug dosing and are estimates, not health targets in themselves. The BMI healthy range from the WHO is the figure most current guidelines use for everyday weight goals. This tool is general information and is not medical advice. For tailored guidance on weight, especially if you have a medical condition, talk to a doctor or a registered dietitian.
Everything you need to find a healthy weight target
Six features that cover ideal weight planning without complexity or signups.
Four classic formulas at once
Hamwi, Devine, Robinson, and Miller, all calculated side by side so you see the full range, not a single number.
WHO BMI healthy range
The 18.5 to 24.9 BMI band shown alongside the formulas, the figure most modern dietitians and doctors actually use.
Metric and imperial
Enter height in centimetres or in feet and inches. Results show in kilograms and pounds together.
Sex-specific results
All four formulas adjust for men and women, since the same height produces different ideal weights.
100% private, runs in browser
Your height and sex stay on your device. Nothing is sent to a server, stored, or shared.
Mobile-friendly layout
Clean responsive design that works on phones, tablets, and desktops.
Who uses an ideal weight calculator?
Anyone setting a weight target who wants more than one opinion.
Setting a weight-loss target
Use the BMI band to pick a goal weight that fits comfortably inside a healthy range rather than chasing one specific number.
Tracking pregnancy recovery
Compare current weight with pre-pregnancy ideal to set a steady, realistic path back over the months after birth.
Medication dosing reference
Some drugs are dosed by ideal body weight rather than total weight. Devine in particular is still used in hospital pharmacies.
Insurance and BMI checks
Life insurance and some employer wellness programs use BMI bands. The calculator shows where you sit in the healthy range.
Coaching and consulting
Trainers and dietitians can use the four-formula comparison to set quick starting targets in a consult.
Sanity-checking a goal
If your goal weight sits below all four formulas and below the BMI band, that is a strong signal the target is unrealistically low.
About ideal weight
A clear guide to the four classic formulas, the BMI range, and how to pick a target.
What is an ideal weight?
Ideal weight is the term medical and fitness sources use for a target weight given a person's height and sex. There is no single perfect number because health depends on body composition, lifestyle, age, and ethnicity as much as it does on weight. The calculator shows four classic formula numbers and the WHO BMI healthy range so you can see a sensible target band rather than chase a single figure.
Hamwi formula (1964)
The Hamwi formula is the oldest of the four. For men, ideal weight starts at 48 kg for a 5-foot height and adds 2.7 kg for every additional inch. For women it starts at 45.5 kg and adds 2.2 kg per inch. The formula was originally built as a quick reference for calculating medication doses for hospital patients, and it still appears in some clinical references today.
Devine formula (1974)
Devine is probably the most commonly used in clinical practice. For men, ideal weight is 50 kg at 5 feet plus 2.3 kg per additional inch. For women, 45.5 kg at 5 feet plus 2.3 kg per additional inch. The formula was published in a journal article on antibiotic dosing and has since become a workhorse for medication calculations in pharmacy and intensive care units around the world.
Robinson formula (1983)
Robinson refined Devine using a larger dataset. Men: 52 kg at 5 feet plus 1.9 kg per inch. Women: 49 kg at 5 feet plus 1.7 kg per inch. The Robinson numbers tend to be slightly higher than Devine for shorter people and lower for taller people, which reflects the curve seen in modern populations.
Miller formula (1983)
Miller, published in the same year as Robinson, used a different dataset. Men: 56.2 kg at 5 feet plus 1.41 kg per inch. Women: 53.1 kg at 5 feet plus 1.36 kg per inch. Miller tends to produce the highest of the four for short heights and the lowest for very tall heights. The contrast between Miller and the older Hamwi is a good illustration of why no single formula is definitive.
The WHO BMI healthy range
The World Health Organisation defines a healthy BMI band of 18.5 to 24.9 for adults. Multiplying by height in metres squared converts the BMI band into a weight range. For a 170 cm adult the band runs from about 53.5 kg to 72 kg, a 19 kg span. The BMI band is the figure most modern dietitians and doctors use because it acknowledges that healthy weight is a range, not a point.
Limits of the formulas
All four classic formulas use only height and sex. They ignore body frame, muscle mass, age, ethnicity, and current body composition. A very muscular athlete will sit well above all four ideal weights without being unhealthy, while a sedentary person can sit right inside the ideal range with high body fat and poor metabolic markers. Use the formulas as references, not as targets to be hit.
Body frame size
Frame size is the rough size of your skeleton, often estimated from wrist circumference. People with a large frame naturally sit at the upper end of any healthy band, and people with a small frame at the lower end. The classic formulas do not adjust for frame, so allow yourself a few kilograms of leeway in either direction if you have a noticeably small or large skeletal structure.
Ideal weight and age
Some research suggests a BMI slightly above 25 may actually be protective in older adults over about age 65, because a small amount of extra mass cushions illness and falls. The classic formulas do not adjust for age. For young and middle-aged adults the BMI band of 18.5 to 24.9 is the standard, but for older adults a BMI of 23 to 27 is sometimes recommended instead.
How to use this calculator
Enter your height and sex and look at the spread of the four formula numbers. They will usually differ by 3 to 6 kg. Then look at the WHO healthy weight band, which is wider. Picking any point inside the band is a reasonable target, and the formula numbers give a sense of where most people sit. Combine the calculator with a body fat measurement and a sense of how strong and energetic you feel at a given weight, because the body responds to those signals as much as it does to a number on a scale.
Frequently asked questions
If you don't find your question here, ask us directly.
A tool that estimates a target body weight for your height and sex using established formulas. This calculator runs four classic formulas at once (Hamwi, Devine, Robinson, Miller) and also shows the healthy weight range from the WHO BMI band of 18.5 to 24.9. You can compare all five numbers and pick a sensible target rather than chasing a single figure.
Each formula was published in a different decade and rests on different assumptions. Hamwi (1964) was built for medication dosing. Devine (1974) is the most commonly cited and still used in clinical practice. Robinson (1983) and Miller (1983) refined the earlier figures with newer data. They disagree by a few kilograms because they reflect different study populations. Comparing all four gives a more honest sense of the range.
There is no single best formula because none was designed to define optimal health. They were built for specific purposes, mainly drug dosing for hospital patients. The BMI healthy range from the WHO is the figure most modern dietitians and doctors use for everyday targets, which is why the calculator shows it as a band alongside the four point estimates.
The BMI range is wider than any single formula because it spans a healthy band rather than a single point. For an average-height adult the band is usually 12 to 18 kg wide. The four formula results almost always fall inside the BMI band, often clustered near its lower half. That is why the band is a more forgiving and realistic target.
At the same height men tend to carry more lean mass and slightly heavier bones, which is why most formulas give a higher figure for men than for women at the same height. The BMI healthy range itself is the same band for both sexes, with men typically sitting higher within it and women lower.
No. The classic formulas use only height and sex. Frame size, the rough size of your skeleton from wrist circumference, shifts a healthy weight by a few kilograms in either direction. Someone with a large frame will sit at the upper end of the BMI band, and someone with a small frame at the lower end. The formula numbers are an average across frames.
Because the formulas use total mass, a very muscular person can appear above their ideal weight while having low body fat and excellent health. This is the same limitation that makes BMI a poor tool for athletes. If you train hard with weights, pair the ideal weight estimate with a body fat measurement to get a real picture.
Each classic formula uses a base weight at 5 feet (60 inches) plus a per-inch increment for every inch above 5 feet. For Devine, men start at 50 kg and add 2.3 kg per inch over 5 feet; women start at 45.5 kg and add 2.3 kg per inch. The BMI band uses the standard equation weight = BMI x height in meters squared, with BMI between 18.5 and 24.9.
The formula outputs do not change with age, but real-world healthy weight does shift through life. Older adults often retain slightly more body fat at the same weight, and there is some evidence that a BMI a little above 25 may be protective after about age 65. For young and middle-aged adults the band 18.5 to 24.9 remains the standard.
The formulas were calibrated decades ago using populations that were on average leaner than people in many countries today. A current weight above the ideal does not necessarily mean unhealthy, especially if body fat is in a healthy range and other markers like blood pressure and cholesterol are fine. Use the BMI band as the practical guide and the formula numbers as additional reference points.
No. The four formulas and the BMI healthy range are for adults aged 18 and older. Children and teens use age- and sex-specific BMI percentiles, which require growth charts from the WHO or CDC and should be interpreted by a pediatrician.
No. Aiming for the lowest of the four formula figures can push you below a healthy body fat percentage, especially for women, and can be hard to maintain. A safer approach is to land anywhere inside the BMI healthy band and feel strong and energetic at that weight. The body works against extremes in both directions.
Yes. Your height, sex, and any other inputs stay in your browser. Nothing is sent to a server, logged, or shared. You can use the calculator without an account and even offline once the page has loaded.
Related tools
Try our other free calculators
BMI calculator, body fat calculator, calorie calculator, and more.