Free Ideal Weight Calculator Online

Ideal Weight Calculator: Devine, Robinson, Miller, and Hamwi Formulas

"Ideal weight" sounds like it should be one number, but the medical literature actually offers several competing formulas, each built decades ago from a different reference population and for a different original purpose. This calculator runs a single height and gender through four of the most cited ones — Devine, Robinson, Miller, and Hamwi — and returns all four results side by side along with their average, so instead of picking one formula and hoping it's the "right" one, you can see how much they agree or disagree for your specific height.

It's worth knowing upfront what these formulas actually were built for. None of them came from a fitness or aesthetics context — they were developed mid-20th-century as quick reference weights for calculating medication dosages in clinical settings, where a rough body-weight estimate was good enough to size a drug dose safely. Using them today as a personal weight target stretches them well past that original job. Treat every figure on this page as an informational estimate, not a personalized health target or medical advice, and talk to a doctor or dietitian about what a healthy weight actually looks like for your body, age, and health history.

How to Get Your Four Ideal Weight Estimates

The tool takes just two inputs, entered as two lines of text:

1. Height in centimeters — the same figure you'd use for a BMI calculation, measured standing without shoes.
2. Gender — "male" or "female" — since every one of the four formulas uses different constants for each.

Submit those two values and the output lists a result for each formula in kilograms: Devine, Robinson, Miller, and Hamwi, followed by a simple average of all four. There's no weight input required at all — unlike BMI, these formulas only ever needed height and gender to produce a reference figure, since they were designed to estimate a "typical" body weight for a given stature rather than evaluate a weight you already have. The calculator also converts your height into inches internally, since three of the four formulas were originally written in imperial units (Hamwi is stated in pounds), and shows that converted figure alongside the results for reference. As with the rest of this tool family, the math runs in your browser the instant you submit the two values — nothing is uploaded anywhere to produce the answer.

Why People Look Up an "Ideal" Weight

Despite the clinical origin of these formulas, people reach for an ideal-weight figure for a range of everyday reasons:

• A starting reference point for a weight goal. Someone beginning a weight-loss or weight-gain plan often wants a rough target number to aim for, even knowing it's approximate, rather than picking a number with no basis at all.
• Comparing several formulas instead of trusting just one. Because Devine, Robinson, Miller, and Hamwi were each calibrated slightly differently, seeing all four together — and how close or far apart they land — gives a better sense of the real range than any single formula alone.
• Cross-checking a number from a doctor's office or drug-dosing context. These formulas are still used clinically for estimating dosing weight in some settings, and this tool lets a patient or caregiver reproduce that same figure independently.
• Understanding how the BMI-based healthy weight range compares. The range this tool produces is calculated completely differently from the 18.5–24.9 BMI-based range shown on a BMI calculator, and comparing the two shows how much they diverge (or don't) for a given height.
• General curiosity about the history of "ideal weight" charts. Height-and-weight charts have circulated since long before modern body-composition science, and running the actual formulas behind them is a quick way to see where those numbers came from.
• Estimating a dosing-relevant body weight for a caregiving situation. A caregiver following medication instructions that reference body weight can use a recognized formula rather than guessing at a round number.

The Four Formulas, Side by Side

All four formulas share a common structure: start from a base weight, then add a fixed amount for every inch of height above five feet (60 inches). Written out, with "over" meaning inches of height beyond 60:

Formula	Men	Women
Devine (1974)	50 + 2.3 × over kg	45.5 + 2.3 × over kg
Robinson (1983)	52 + 1.9 × over kg	49 + 1.7 × over kg
Miller (1983)	56.2 + 1.41 × over kg	53.1 + 1.36 × over kg
Hamwi (1964)	106 + 6 × over lb	100 + 5 × over lb

Hamwi's original formula is stated in pounds rather than kilograms — this tool converts the pound figure to kilograms after computing it so all four results share the same unit for easy comparison. Take a 175 cm tall man as an example: that's 68.9 inches, or 8.9 inches "over" the 60-inch baseline. Devine gives 50 + 2.3 × 8.9 = 70.5 kg. Robinson gives 52 + 1.9 × 8.9 = 68.9 kg. Miller gives 56.2 + 1.41 × 8.9 = 68.7 kg. Hamwi gives 106 + 6 × 8.9 = 159.4 lb, which converts to roughly 72.3 kg. Averaging the four lands at 70.1 kg — a spread of about 3.6 kg between the lowest and highest formula for the exact same height and gender, which is itself the clearest illustration of why no single one of these should be treated as a definitive number.

Why Four Different Formulas Exist

Devine's formula, published in 1974, was created specifically to estimate lean body weight for calculating drug dosages — particularly for medications like aminoglycoside antibiotics, where dosing by total body weight in an overweight patient risks overdosing. Robinson and Miller followed a decade later, each proposing adjustments based on different reference datasets and slightly different assumptions about "normal" body proportions at a given height. Hamwi's formula predates all three, developed in 1964 as a quick bedside estimate for dietitians rather than a precision clinical tool. None of the four was built with fitness, bodybuilding, or personal weight goals in mind, and none of them accounts for frame size, muscle mass, age, or the body-composition factors that a modern approach to healthy weight would consider.

That history matters because it explains the gap between what these formulas were built to do and how they get used today. A drug-dosing estimate from 1974 and a bodybuilder's target walk-around weight are different questions, even though both might get typed into a search bar as "ideal weight." This tool answers the first question with real, citable formulas; it cannot answer the second, because no formula that only knows height and gender realistically can. Modern approaches to a genuinely personalized healthy-weight range tend to fold in waist circumference, body fat percentage, activity level, and family health history — a far longer list of inputs than any of these four equations was ever designed to take.

Reading a Chart by Hand vs. Running the Formulas

Ideal-weight figures show up in a few different forms, each with its own limitations:

• A printed height-weight chart. Common in older medical offices and insurance tables, these give a quick lookup but are usually built around a single formula and don't show how much the answer would change under a different one.
• Manually computing one formula. Devine's formula alone is simple enough to do on a calculator, but computing all four by hand to compare them is tedious enough that most people just trust whichever one they found first.
• A doctor's clinical estimate. A physician may reference one of these formulas (often Devine) for a specific clinical purpose like medication dosing, using the exact figure needed for that context rather than a general-purpose target.
• This calculator. All four formulas computed at once, plus an average, with the same math available as a metered API endpoint for anyone building a health or fitness app that needs the identical reference figures programmatically — the request format is documented at /docs.

Why do these formulas only use height and gender, and not age?

Because they were designed as quick clinical reference points rather than a full health assessment, and adding age would have complicated the original bedside or dosing calculation they were meant for. Body composition does shift with age even at a constant height, which is one more reason a decades-old two-variable formula shouldn't be read as a precise, individualized target.

Which of the four formulas should I actually trust?

None of them is more "correct" than the others in an absolute sense — they're different statistical fits to different reference populations from different decades. Devine is the most widely cited in modern clinical dosing contexts, but for a general sense of a reasonable weight range, the average of all four (shown alongside the individual results) is often more informative than picking just one.

Why doesn't this calculator ask for my current weight?

Because these particular formulas were never designed to evaluate a weight you already have — they estimate a reference weight from height and gender alone. If you want to know where your current weight falls relative to a standard range, the BMI Calculator is built for exactly that comparison.

Does this account for muscle mass or body frame size?

No. All four formulas use only height and gender, so a heavily muscled person and a person with very little muscle at the identical height get the identical "ideal weight" figures, even though a healthy weight for each of them in practice would likely differ. For a frame-size-aware estimate, see the Body Type Calculator.

Why is there such a big gap between the Hamwi and Miller results?

Each formula was calibrated against a different dataset with a different per-inch weight increment, so the gap widens the further your height sits from 60 inches (five feet) — the baseline all four formulas start from. Shorter and taller-than-average heights tend to show a bigger spread between formulas than heights near the middle of the range.

Is this a substitute for a doctor's weight recommendation?

No. These are general-purpose reference formulas from clinical dosing literature, not a personalized assessment. A doctor or dietitian can factor in your medical history, muscle mass, activity level, and other details that height and gender alone can never capture — always treat this page as informational, not a health directive.

Do these formulas work for someone under five feet tall?

They still compute a number, but the "over 60 inches" structure they're all built on means a height right at or below that baseline produces very little adjustment from the base constant, and the original research behind these equations focused on typical adult heights rather than the shorter or taller extremes of the range. Treat results near either edge of the height spectrum as even rougher approximations than usual.

Related Tools

An "ideal weight" figure is more useful alongside the tools that measure what these formulas leave out. Check body composition directly with the Body Fat Calculator, or get a frame-size-adjusted read with the Body Type Calculator. To compare against the standard weight-to-height ratio most clinics use, see the BMI Calculator, and to translate any target weight into a daily calorie plan, the Calorie Calculator picks up where this page leaves off.