2026-08-20 · ideal weight calculator, ideal body weight, IBW, Hamwi formula, Devine formula, healthy BMI range, goal weight

What is ideal body weight and how is it calculated?

Ideal body weight (IBW) is a historical clinical estimate of what a healthy adult of a given height and sex should weigh, produced by simple linear formulas — Hamwi 1964, Devine 1974, Robinson 1983, and Miller 1983. Each starts from a base weight at 5 ft (roughly 100 lb for women and 106 lb for men) and adds a fixed increment per additional inch. It was built for clinical drug dosing, not for weight-loss goals.

Which ideal body weight formula is most accurate?

None is a body-composition measurement, so no formula is 'accurate' in the way a DEXA scan is. Devine 1974 is the most widely used in modern medicine because it anchors aminoglycoside antibiotic dosing (Winter 2004, Pharmacotherapy). Hamwi is the fastest to run mentally. At typical adult heights the four formulas usually land within ±5 kg of each other, so the choice matters less than the concept.

What is the difference between ideal body weight and healthy BMI range?

Ideal body weight is a single number from a 1960s–1980s clinical formula. The healthy BMI range (18.5–24.9 kg/m² per WHO 1995 and NIH 1998) is a range of about 30–40 lb wide at any given height. Modern clinical guidelines use the range, not the single number, because population mortality data (Aune 2016, BMJ) show the lowest all-cause mortality across the whole band, not at one point.

Is ideal body weight the same as goal weight?

No. Ideal body weight is a clinical dosing estimate that ignores muscle mass, body composition, and fat distribution. A realistic personal goal weight is a range you can maintain that also improves your cardiometabolic markers — often 5–10% below your current weight, per Look AHEAD (Wing 2011) and the Diabetes Prevention Program (Knowler 2002). That target usually sits higher than the IBW number the formulas produce.

Do the formulas work for very tall or very short adults?

Not reliably. All four formulas are linear extrapolations from a 5 ft anchor, so at heights under about 5 ft or over 6 ft 6 the four numbers diverge from each other and from the healthy BMI range. The healthy BMI range is a better tool at height extremes because it scales with height squared instead of adding a flat increment per inch. Use the BMI-range readout on this calculator at those heights.

How is ideal body weight used in medicine?

Four current clinical uses. First, drug dose calculations for water-soluble medications like aminoglycoside antibiotics and low-molecular-weight heparin (Winter 2004). Second, mechanical-ventilation tidal-volume settings at 6–8 mL per kg IBW (ARDSNet 2000, NEJM). Third, adjusting creatinine-clearance estimates via Cockcroft-Gault. Fourth, parenteral and enteral nutrition dosing in critically ill patients. None of these uses translate to weight-loss goal-setting.

What is a healthy weight range for my height?

The healthy BMI range at your height is 18.5–24.9 kg/m². For a 5 ft 6 in adult that is roughly 115–154 lb (52–70 kg). For a 5 ft 10 in adult it is roughly 129–174 lb (58–79 kg). Enter your height in the calculator on this page for the range at your exact height. Where you sit inside the range depends on muscle mass, waist circumference, and other cardiometabolic markers — the middle of the band is not automatically better than the edges.

Should I aim for my ideal body weight as a weight-loss goal?

Usually not. The four formulas were built for adult drug dosing and were never validated as weight-loss goals. A single-number IBW target can push you below what your body will comfortably maintain and ignores body composition entirely. A more evidence-supported plan is to aim for a 5–10% loss from your starting weight, then reassess using the healthy BMI range plus waist circumference — see the guidance section on this page.

Ideal Weight Calculator: Hamwi, Devine, Robinson, Miller Formulas Plus Healthy BMI Range

“Ideal body weight” is a historical clinical concept, not a modern weight-loss goal. The four formulas below (Hamwi 1964, Devine 1974, Robinson 1983, Miller 1983) were built for drug dosing and mechanical-ventilation settings, and each produces a single number for an adult of a given height and sex. This calculator returns all four, plus the healthy BMI range at your height (18.5–24.9 kg/m² per WHO 1995 and NIH 1998) — which is the number most modern clinical guidelines actually use. Enter your height, pick a sex, and read all five figures side by side.

Looking for more tools? See all seven free weight-loss calculators in one place.

What “ideal body weight” actually means

“Ideal body weight” (IBW) is a historical clinical concept, not a body-shape or aesthetic target. The four formulas the calculator above uses — Hamwi 1964, Devine 1974, Robinson 1983, and Miller 1983 — were each built for a specific hospital use case. Devine’s original 1974 paper in Drug Intelligence and Clinical Pharmacy proposed the formula for gentamicin dosing in patients who were over- or underweight, because dose calculations for water-soluble antibiotics need a lean-mass estimate rather than a total-body-weight number. Robinson and Miller followed in 1983 to serve hospital nutrition and dosing (Robinson 1983, Am J Hosp Pharm).

Winter 2004 (Pharmacotherapy) is the reference that anchors modern usage: IBW is used to bias-correct creatinine-clearance estimates from the Cockcroft-Gault equation, and it is the input for aminoglycoside and low-molecular-weight-heparin dosing. None of that translates to a weight-loss goal. If your reason for looking up IBW is “how much should I weigh,” the healthy BMI range at your height is a better answer — that number sits inside every result panel above.

How to use the calculator

1. Enter your height. Use the metric/imperial toggle to switch between cm and feet + inches.
2. Select your sex. All four historical formulas are sex-specific — women have a lower base weight at 5 ft and a smaller per-inch increment than men.
3. Choose a body frame. Leave it on medium unless you know your frame differs. Small applies −10% and large applies +10% — a historical Metropolitan Life Insurance adjustment from the 1959 and 1983 height–weight tables (Harrison 1985, Am J Clin Nutr). It is a rough correction, not a body-composition measurement.
4. Read all five numbers. The four formulas will usually cluster inside about a ±5 kg (~11 lb) window at typical adult heights. The healthy BMI range is a 30–40 lb band around the same height. If your existing weight is inside the healthy BMI range, the four IBW numbers are context, not a target.

The four historical formulas — where each one came from

Each formula was published for a specific clinical purpose, and each one predates BMI as the primary adult weight-assessment tool (Keys 1972 coined the term; WHO 1995 formalized the healthy-range cutoffs).

Devine’s formula is the one you will meet most often in a modern hospital because it drives aminoglycoside dosing; Hamwi’s is the one clinicians reach for in the corridor because you can run it in your head. Robinson and Miller are close variants of the same idea with slightly different coefficients.

How the formulas compare

Four rows and the same two example adults — a 5 ft 6 in (168 cm) female and a 5 ft 10 in (178 cm) male — run through each formula, medium frame, no adjustment.

Two things stand out. First, at typical adult heights the four formulas land within a ~5 kg (~11 lb) window of each other. Second, the single-number IBW estimates sit near the low-middle of the healthy BMI range — the healthy BMI band is meaningfully wider than the spread of the four historical formulas, and it always extends higher. At heights outside about 5 ft to 6 ft 6 the four formulas diverge more sharply from each other and from the BMI range, because they are linear extrapolations from a 5 ft anchor while BMI scales with height squared. Use the BMI-range readout at the height extremes.

Ideal weight vs healthy BMI range

The healthy BMI range — 18.5–24.9 kg/m² — is the number modern clinical guidelines (WHO 1995 and 2004; NIH NHLBI 1998; USPSTF 2021) actually use for adult weight assessment. It is a range about 30–40 lb wide at typical adult heights, and the range is the point.

Two anchor studies. Aune 2016 (BMJ), a systematic review and dose-response meta-analysis of BMI and all-cause mortality across 230 cohort studies and more than 30 million adults, found the lowest all-cause mortality across a wide plateau inside the healthy BMI range — not at a single point, and not systematically at the middle. Flegal 2013 (JAMA), a meta-analysis of 97 studies, reported the “obesity paradox” caveat: adults with BMI 25–29.9 had lower all-cause mortality than adults with BMI in the 18.5–24.9 healthy range in several subgroups, particularly older adults.

Read together, those two papers are why modern practice uses the range, not a single ideal number. If your weight is inside the healthy BMI range at your height, chasing a specific IBW figure below that range is not evidence-supported.

Why “ideal weight” is a misleading term for weight-loss goals

Three specific reasons the four formulas mislead when used for weight-loss goal-setting.

1. They ignore body composition entirely. All four formulas use only height and sex. A 5 ft 6 in muscular adult and a 5 ft 6 in sedentary adult get the same IBW number, and the number is meaningless for both. Lean mass and fat mass are the variables that actually drive cardiometabolic risk (Aune 2016). For a composition readout, see the body-fat percentage calculator — the U.S. Navy tape method returns a percentage that IBW cannot approximate.
2. The single-number output can drive unrealistic goals. A 5 ft 4 in female with a Devine IBW of 120 lb may realistically maintain 135–145 lb after healthy weight loss — a weight that sits comfortably inside the healthy BMI range (108–145 lb at that height) and produces meaningful cardiometabolic benefit (Wing 2011 Look AHEAD; Knowler 2002 DPP), without pushing against her body’s set-point. Chasing the IBW number instead can produce restrictive eating patterns for zero additional health return.
3. The formulas were built for adult drug dosing. Using them as weight-loss goals is a category error — like using a fuel-tank capacity to plan a road-trip route. They were validated for dose-per-kilogram calculations in a hospital context, not for what an adult should weigh at home.

The clearer target for weight-loss goal-setting is the healthy BMI range plus a waist-circumference target, not a single IBW number.

What clinicians actually use “ideal body weight” for today

Four current clinical uses, none of which involve weight-loss goal-setting.

1. Drug dose calculations for water-soluble medications. Aminoglycoside antibiotics (gentamicin, tobramycin, amikacin), low-molecular-weight heparin, and several other agents are dosed on IBW rather than total body weight because their distribution volumes track lean mass (Winter 2004, Pharmacotherapy). This is the primary modern use.
2. Mechanical-ventilation tidal-volume settings. The ARDSNet 2000 protocol (NEJM), which reduced mortality in acute respiratory distress syndrome, sets tidal volume at 6–8 mL per kg of IBW — not total body weight — because lung volume tracks height, not adiposity. This is the anchor citation for “lung-protective ventilation” in modern critical care.
3. Creatinine-clearance estimation. The Cockcroft-Gault equation for creatinine clearance uses total body weight by default but is bias-corrected with IBW in adults with elevated adiposity to avoid over-estimating renal function (Winter 2004).
4. Parenteral and enteral nutrition dosing. Calorie and protein prescriptions in critically-ill adults on tube feeds or IV nutrition are typically written per kg of IBW to avoid over-feeding adults with high total body weight.

If you ever wonder why a hospital chart lists an “IBW” figure alongside your actual weight, one of these four is the reason.

The Metropolitan Life height-weight tables

Before BMI became the primary adult weight-assessment tool in the 1990s, the reference was the Metropolitan Life Insurance Company height-weight tables — first published in 1943, revised in 1959, and revised again in 1983. The tables listed a “desirable weight” range for each height, broken down by sex and by small/medium/large frame — which is where the ±10% body-frame adjustment on this calculator comes from.

Harrison 1985 (Am J Clin Nutr) is the most-cited critique of the Met Life tables: the underlying data came from life-insurance applicants, a self-selected non-representative sample, and the “desirable weight” figures were reverse-engineered from actuarial mortality data with methodological limitations that would not clear peer review today. The WHO Expert Consultation (WHO 1995) and NIH NHLBI 1998 both replaced the Met Life framework with BMI cutoffs. The IBW formulas persisted in clinical dosing because they are quick to run — not because they are better than BMI for weight assessment.

How to set a weight-loss goal without using “ideal weight”

If you are trying to set a target weight, run this four-step alternative rather than reading a single IBW number.

1. Aim for the healthy BMI range at your height (18.5–24.9 kg/m²) as a broad target, not a single number. Use the BMI calculator to see the range in pounds for your exact height. Where you land inside that range depends on muscle mass, waist size, and other markers — the middle is not automatically better than the edges.
2. Add a waist-circumference target. Men under 40 in (102 cm) and women under 35 in (88 cm) per NIH 2000 guidelines. Waist size captures the distribution signal that BMI misses — see the waist-to-hip ratio calculator for the paired ratio.
3. Consider a body-fat-percentage target if you have access to a good measurement. Men 10–20%, women 18–28% per ACSM 2021. DEXA is the gold standard; a tape-method estimate from the body-fat percentage calculator is a reasonable home approximation.
4. Use 5–10% total body-weight loss from baseline as the first practical target. The Look AHEAD 4-year outcomes (Wing 2011, Diabetes Care) and the Diabetes Prevention Program (Knowler 2002, NEJM) both produced meaningful cardiometabolic benefit — lower HbA1c, blood pressure, triglycerides, and sleep-apnea severity — at this magnitude of loss, regardless of the starting BMI. This is the most-evidenced clinical goal in adult weight loss.

For the fuller reference on which numbers matter and which come from which trial, see the weight-loss guidelines and numbers cheat sheet. And for the deficit math that turns a target into a daily calorie plan, see how many calories to lose weight.

Frequently asked questions

What is ideal body weight and how is it calculated? Ideal body weight (IBW) is a historical clinical estimate of what a healthy adult of a given height and sex should weigh, produced by simple linear formulas — Hamwi 1964, Devine 1974, Robinson 1983, and Miller 1983. Each starts from a base weight at 5 ft (roughly 100 lb for women and 106 lb for men) and adds a fixed increment per additional inch. It was built for clinical drug dosing, not for weight-loss goals.

Which ideal body weight formula is most accurate? None is a body-composition measurement, so no formula is “accurate” in the way a DEXA scan is. Devine 1974 is the most widely used in modern medicine because it anchors aminoglycoside antibiotic dosing (Winter 2004, Pharmacotherapy). Hamwi is the fastest to run mentally. At typical adult heights the four formulas usually land within ±5 kg of each other, so the choice matters less than the concept.

What is the difference between ideal body weight and healthy BMI range? Ideal body weight is a single number from a 1960s–1980s clinical formula. The healthy BMI range (18.5–24.9 kg/m² per WHO 1995 and NIH 1998) is a range of about 30–40 lb wide at any given height. Modern clinical guidelines use the range, not the single number, because population mortality data (Aune 2016, BMJ) show the lowest all-cause mortality across the whole band, not at one point.

Is ideal body weight the same as goal weight? No. Ideal body weight is a clinical dosing estimate that ignores muscle mass, body composition, and fat distribution. A realistic personal goal weight is a range you can maintain that also improves your cardiometabolic markers — often 5–10% below your current weight, per Look AHEAD (Wing 2011) and the Diabetes Prevention Program (Knowler 2002). That target usually sits higher than the IBW number the formulas produce.

Do the formulas work for very tall or very short adults? Not reliably. All four formulas are linear extrapolations from a 5 ft anchor, so at heights under about 5 ft or over 6 ft 6 the four numbers diverge from each other and from the healthy BMI range. The healthy BMI range is a better tool at height extremes because it scales with height squared instead of adding a flat increment per inch. Use the BMI-range readout on this calculator at those heights.

How is ideal body weight used in medicine? Four current clinical uses. First, drug dose calculations for water-soluble medications like aminoglycoside antibiotics and low-molecular-weight heparin (Winter 2004). Second, mechanical-ventilation tidal-volume settings at 6–8 mL per kg IBW (ARDSNet 2000, NEJM). Third, adjusting creatinine-clearance estimates via Cockcroft-Gault. Fourth, parenteral and enteral nutrition dosing in critically ill patients. None of these uses translate to weight-loss goal-setting.

What is a healthy weight range for my height? The healthy BMI range at your height is 18.5–24.9 kg/m². For a 5 ft 6 in adult that is roughly 115–154 lb (52–70 kg). For a 5 ft 10 in adult it is roughly 129–174 lb (58–79 kg). Enter your height in the calculator on this page for the range at your exact height. Where you sit inside the range depends on muscle mass, waist circumference, and other cardiometabolic markers — the middle of the band is not automatically better than the edges.

Should I aim for my ideal body weight as a weight-loss goal? Usually not. The four formulas were built for adult drug dosing and were never validated as weight-loss goals. A single-number IBW target can push you below what your body will comfortably maintain and ignores body composition entirely. A more evidence-supported plan is to aim for a 5–10% loss from your starting weight, then reassess using the healthy BMI range plus waist circumference — see the guidance section on this page.