Ideal Weight Calculator
Calculate ideal body weight using four established formulas — Devine, Hamwi, Robinson and Miller — adjusted for your actual frame size, with a target BMI and a direct comparison to your current weight.
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Where These Four Formulas Actually Came From
Ideal Body Weight was not originally invented as a fitness goal — the Devine formula, still the most widely used of the four, was published in 1974 purely to help clinicians dose medication based on body size rather than actual weight, which can be skewed by fluid retention or excess fat. Hamwi's 1964 version came out of nutrition assessment work, Robinson's 1983 formula was built from actuarial and insurance mortality datasets, and Miller's 1983 formula — which consistently produces the highest numbers of the four — drew from a population that included more heavily built individuals. None of them was designed with the others in mind, which is exactly why running all four together and averaging gives a steadier reference than committing to any single one.
Why Frame Size Changes the Answer
All four formulas take only height and sex as input, which means they quietly assume everyone at a given height has roughly the same skeletal build — and that assumption breaks down more than people expect. A large-framed adult carries more structural bone and joint mass without any extra body fat, so a formula tuned to an average frame will underestimate what is actually healthy for them; the opposite happens for a naturally small frame. The ±10% adjustment used here is a long-standing clinical approximation, not a precise measurement, but it meaningfully narrows the gap between "average person at this height" and "you at this height" — which is the entire point of adding it rather than stopping at a single averaged number the way most free calculators do.
Two Examples Worth Walking Through
The frame-adjustment case: a 178 cm man with a genuinely large frame (wrist around 19.5 cm) gets a four-formula average of about 74 kg. Left unadjusted, that number undersells what is structurally normal for him — the large-frame adjustment lifts his target closer to 81 kg, a meaningfully different and more realistic reference point for the same height.
The composition mismatch case: a competitive powerlifter at 170 cm and 88 kg sits well above even the highest (Miller) formula estimate for his height. His BMI reads in the "obese" range. Neither number is wrong on its own terms, but neither is useful for him either — his actual body fat percentage, checked separately, is under 15%. This is exactly the population the classic IBW formulas were never built to describe, and exactly why pairing this result with a Body Fat Calculator reading matters for anyone with an athletic build.
IBW, BMI and Body Fat — Which Number Should You Actually Trust?
Run the same person through all three tools and it is common to get three slightly different verdicts — and that is not a contradiction, it is three different questions being asked. Ideal Body Weight asks "what would a typical person of your height and sex weigh?" using decades-old population regressions. BMI asks a narrower question — "does your weight sit inside a broad band linked to lower population health risk?" — without any reference to sex, frame or age at all. Body fat percentage asks something closer to the real question most people actually care about: "how much of you is fat versus everything else?" None of the three is more "correct" than the others; they simply measure different things and were built for different jobs, one of them (Devine, in particular) not even originally for individuals at all.
A practical way to use all three together: treat the IBW range from this calculator as a quick, frame-aware starting point when you have no other data, lean on BMI as a fast population-level sanity check, and treat body fat percentage as the tie-breaker whenever the first two disagree with how you actually look, feel or perform. If your IBW target, BMI category and body fat reading broadly agree, that convergence is a reasonably strong signal. If they pull in different directions — most often for very muscular, very tall, or very short people — that disagreement itself is the useful information, and it usually means body composition, not just body weight, is the number worth following.
Who Actually Uses an Ideal Weight Calculator
- People setting a weight goal for the first time — a sanity-checked starting target instead of a single guessed number.
- Anyone preparing for a medical or nutrition consultation — arriving with a reference range already in hand.
- People comparing IBW against their BMI or body fat reading — checking whether the different systems roughly agree.
- Clinicians and dietitians (informally) — the Devine formula in particular remains common in dosing and nutrition-assessment contexts.
Once you have a target weight in mind, our Calorie Calculator and BMR Calculator turn that number into a daily calorie target to actually work toward it.
What These Formulas Cannot See
Every formula here is built from height and sex alone — none of them knows your muscle mass, bone density, age, ethnicity or where you carry fat. That is a real limitation, not a minor caveat: someone within their IBW range can still have high body fat and low muscle (sometimes called "normal weight obesity"), while someone well above it can be lean, strong and in excellent health. Treat the target and range here as a starting reference to weigh alongside other measurements, such as BMI and body fat percentage, rather than a number to chase for its own sake.
Age and ethnicity add another layer none of the four formulas touches. Bone density and muscle mass both decline gradually after roughly age 40, so a target built purely from height and sex can end up pointing at a weight that suited someone's 30-year-old frame rather than their current one — some clinicians informally nudge expectations downward for older adults for exactly this reason, even though none of the formulas builds that adjustment in automatically. Ethnic background matters too: population research has found healthy body composition at a given height varies somewhat between groups, which is part of why BMI itself has a separate Asian-Pacific threshold set with lower cut-offs. None of this makes the target here useless — it simply means the number is a well-reasoned estimate for an average body at your height and sex, not a personalised clinical judgment. If you are managing a specific health condition, recovering from disordered eating, or planning a significant intentional weight change, loop in a healthcare provider or registered dietitian rather than treating any calculator's output — this one included — as medical guidance.