Which ideal weight formula is the right one?

None of them, strictly. They were developed for clinical purposes such as drug dosing and ventilator settings, not to tell individuals what to weigh. Showing four side by side makes the point: they disagree by several kilograms at the same height, which is itself the most useful result.

Why is the healthy BMI range so much wider?

Because it reflects what the evidence actually supports. The formulas produce a single number, while mortality and health outcome data show a broad plateau spanning 18.5 to 24.9 BMI — often a span of 20 kilograms or more. There is no single correct weight for a given height.

Where did these formulas come from?

Hamwi (1964) was devised for estimating insulin requirements in diabetes. Devine (1974) was created for calculating drug doses and is still used that way in pharmacy. Robinson and Miller, both 1983, were attempts to fit the data better. All four are anchored at a height of five feet and add a fixed amount per inch above it.

Do these formulas account for build or muscle?

No. They use height and sex only, so they cannot distinguish a heavily muscled frame from a slight one. Someone lifting seriously will often exceed every figure here while carrying low body fat. Body fat percentage is the more meaningful measure for that question.

Should I use this to set a weight goal?

Use the healthy BMI range as the target zone and treat the formulas as historical context. A goal anywhere inside that range is defensible, and where you sit within it is better decided by how you feel, perform and measure on body composition than by a formula from 1974.

Ideal Weight Calculator: Four Formulas Compared

How to use this calculator

Choose units and enter your sex at birth.
Enter your height. In imperial this is total inches — five foot ten is 70.

Four formulas are shown alongside the healthy BMI range, because the comparison between them is more informative than any single figure.

How the calculations work

All four formulas share a structure: a base weight at five feet tall, plus a fixed amount for every inch above that.

Formula	Male	Female
Hamwi (1964)	48.0 kg + 2.7 kg/in	45.5 kg + 2.2 kg/in
Devine (1974)	50.0 kg + 2.3 kg/in	45.5 kg + 2.3 kg/in
Robinson (1983)	52.0 kg + 1.9 kg/in	49.0 kg + 1.7 kg/in
Miller (1983)	56.2 kg + 1.41 kg/in	53.1 kg + 1.36 kg/in

The healthy BMI range is calculated separately, as the weights giving a BMI between 18.5 and 24.9 at your height.

A worked example

A male at 175 cm, which is 68.9 inches — 8.9 inches over five feet.

Devine   = 50.0 + 2.3   × 8.9 = 70.5 kg
Robinson = 52.0 + 1.9   × 8.9 = 68.9 kg
Miller   = 56.2 + 1.41  × 8.9 = 68.7 kg
Hamwi    = 48.0 + 2.7   × 8.9 = 72.0 kg


Average of the four	70.0 kg
Devine (1974)	70.5 kg
Robinson (1983)	68.9 kg
Miller (1983)	68.7 kg
Hamwi (1964)	72.0 kg
Healthy BMI range	56.7 kg – 76.3 kg

The four formulas span 3.3 kilograms. The healthy BMI range spans 19.6 kilograms — six times wider.

That contrast is the most useful output on this page. Four respected formulas cannot agree on a single number, and the evidence base underneath them supports a broad plateau rather than a point.

Where these formulas came from

None of them were created to tell individuals what to weigh.

Hamwi (1964) was devised for estimating insulin requirements in people with diabetes.

Devine (1974) was created for calculating drug dosages, and it is still used that way in clinical pharmacy today — for aminoglycoside antibiotics and chemotherapy agents, where dosing on actual body weight would be unsafe for heavier patients. This is the formula’s real and continuing purpose.

Robinson (1983) and Miller (1983) were attempts to fit population data more closely after Devine’s equation became widespread.

They are clinical conveniences that escaped into popular use. Treating them as a personal target is applying a drug-dosing heuristic to a question it was never asked.

What they cannot account for

Build and muscle mass. Height and sex are the only inputs. A heavily muscled person will exceed every figure here while carrying low body fat, and the formulas have no way to know.

Frame size. Skeletal width varies considerably between people of the same height, which older height-weight tables at least attempted to address with small, medium and large frame categories.

Age. Body composition shifts through life, and modest additional weight in older adults is associated with better outcomes, not worse.

Anything about health. Blood pressure, fitness, blood markers and waist circumference all tell you more about health than a target weight does.

Are they valid at the extremes?

They become unreliable. Every formula extrapolates from a five-foot baseline, so well below that height they can produce implausibly low figures, and at great heights they drift from what BMI would suggest.

Between roughly five feet and six foot four they broadly agree with the healthy BMI range, which is the span where they are worth looking at.

A more useful way to set a target

Use the healthy BMI range as the zone, then decide where in it you want to sit based on things that are actually measurable about you: how you feel, how you perform, waist circumference, and body fat percentage.

A goal anywhere inside that range is defensible. Choosing a point within it is a personal decision informed by body composition, not an equation from 1974.

Common mistakes to avoid

Treating the average as the answer. It is the mean of four disagreeing estimates, not a consensus. It is shown because people ask for one number, not because one number is right.

Entering height in feet instead of total inches. In imperial mode, 5.10 is not five foot ten — it is five and a tenth inches, and the result will be nonsense.

Setting a target below the healthy BMI range. All four formulas sit comfortably inside it at normal heights. If a goal you have set falls below the bottom of that range, the formulas are not what put it there.

When this calculator is not the right tool

For assessing your current status, BMI is the faster screen and body fat percentage is the more informative measure. For a weight change plan, the calorie calculator works from energy expenditure rather than a target weight. And for clinical drug dosing, use the specific formula your protocol requires — usually Devine — rather than the average shown here.

Ideal Weight Calculator