Ideal Weight Calculator
Ideal weight by four published formulas at once, shown as a range rather than a single number.
Free forever, no sign-up and no limits, and this tool installs on its own so you can keep it on your home screen.
Four published ideal weight formulas at once, plotted against the healthy BMI range for your height, because they disagree with each other by several kilograms and any single answer hides that. The useful output is a range, not a target.
How to use it
- Pick sex and unitsBoth formulas and ranges differ by sex.
- Enter your heightThat is all four formulas need.
- Read the spreadThe shaded bar is the healthy BMI range. The dots are what each formula says.
The disagreement is the information
Type a height into most ideal weight calculators and you get one number to one decimal place. That number is a choice the site made among several published formulas, and it does not tell you it made one. At 180 centimetres the four here span several kilograms, and seeing them scattered inside the healthy BMI band is a more truthful picture than any point in the middle of it.
This is why the chart is the output rather than a decoration. The dots are the formulas, the bar is the BMI range, and what you are meant to take away is roughly where you fit rather than a figure to hit.
Where these numbers actually came from
Almost every widely used ideal weight formula started life in clinical dosing rather than in nutrition. Devine's 1974 equation was published to work out drug doses from body size, and it was presented without derivation. Hamwi's came from a 1964 method for estimating insulin needs. They spread because they were simple and because something was needed, not because anybody had shown that people at those weights were healthier.
That is not a reason to throw them away. It is a reason to treat them as a rough bracket, which is how the clinicians who use them treat them.
The BMI band does more work
The shaded range on the chart is the weight that gives a BMI between 18.5 and 25 at your height, and it is wider than the formulas because it was derived from population health data rather than from arithmetic convenience. If you want one thing to look at, look at whether you fall inside it. The dots are there to show how much any single formula narrows that band arbitrarily.
What this cannot do
It cannot see muscle, frame, or where weight sits, and it cannot know anything about you beyond your height. It applies to adults only. And it is not a goal setting tool: if you are trying to change your weight, the number worth watching is the direction over months, not the distance to a dot on a chart.
Questions people ask
Why four formulas instead of one?
Because there are at least four in common use and they disagree. Hamwi came from 1964 as a bedside rule for insulin dosing, Devine from 1974 for drug calculations, Robinson and Miller from 1983 as attempts to fit real population data better. None was designed as a health target for the general public. Showing one of them alone implies a precision that does not exist.
Which one should I use?
None of them on its own. The honest answer is the range they cover, read together with the healthy BMI band, which is the wider shaded bar on the chart. If your weight sits inside that band you are in the range these formulas were trying to describe.
Where did these formulas come from?
Clinical medicine rather than fitness. Devine's was published to standardise drug dosing by body size, and it was an estimate offered without much derivation that became a standard through use. That history is worth knowing: they are rules of thumb from prescription pads, not conclusions from studies of health outcomes.
Why do they all start from five feet?
All four are written as a base weight plus so much per inch over five feet, which is a convenient form and a slightly odd one. It means they behave least well at the extremes of height, and for anybody well under five feet the formulas can return figures that are clearly too low.
Is there one ideal weight for a person?
No, and that is the most useful thing on this page. Health outcomes across a healthy BMI band are broadly similar, body composition matters more than the number, and where somebody feels well and functions well varies. A range is the true shape of the answer.
Does this account for frame size or muscle?
No. None of the four formulas takes anything but height and sex. Somebody carrying a lot of muscle will sit above all four while being perfectly healthy, which is the same limitation BMI has and one reason the body fat tool exists.
What about children?
This is for adults. Children are assessed on growth charts by age and sex, and a formula built for adult drug dosing has nothing sensible to say about a growing body.