September 2026 10 min read

Ideal Weight Calculator

Find your ideal body weight using the four classic clinical formulas — Hamwi, Devine, Robinson, and Miller — alongside the WHO healthy BMI weight range, a frame-size adjustment, and a comparison with your current weight.

Enter Your Details

Gender

Male Female

Age

years

Height

Current Weight

Optional — used for comparison against your ideals.

Wrist Circumference

Optional — estimates frame size for the ±10% adjustment.

Auto-calculate

Ideal Weight Formulas

Every classic IBW formula shares one structure: a base weight at 5 feet, plus a fixed increment for each inch above it. The four differ only in their base and increment values.

IBW = base + increment × (H − 60 inches)

Alternative Form

Healthy BMI range: 18.5 × H(m)² to 24.9 × H(m)²

Variables

Symbol	Name	Unit	Description
IBW	Ideal Body Weight	kg	The formula reference weight for a given height and sex
base	Base Weight	kg	Weight assigned at exactly 5 feet (varies by formula and sex)
Δ	Per-Inch Increment	kg/inch	Weight added for each inch over 5 feet
H	Height	inches	Total height in inches; inches over 60 drive the increment

Explanation

Devine (1974) is the clinical workhorse; Hamwi (1964) is the oldest with the steepest male slope; Robinson and Miller (both 1983) recalibrated Devine downward for taller heights. Because all are linear, they agree closely near average heights and diverge at the extremes — which is why this calculator reports all four plus their average, framed by the WHO healthy BMI weight range.

Derivation

The formulas descend from insurance actuarial height-weight tables of the mid-20th century. Devine derived his coefficients for dosing water-soluble drugs, which distribute primarily in lean tissue — a weight-height proxy was needed at the bedside. Robinson et al. and Miller et al. re-fitted the base and slope on more modern samples. The healthy BMI range (18.5-24.9 × height in meters squared) is the population-based alternative that replaced single-number ideals in modern practice.

Step-by-Step Calculation

Follow each step to understand how the result is calculated from your inputs.

Step 1

Convert height to total inches and find the amount over 5 feet.

over = H(inches) − 60

Height:5'10" = 70 in

Intermediate: 70 − 60

Result: over = 10 inches

Step 2

Apply the Devine formula for a man.

IBW = 50.0 + 2.3 × over

Base:50.0 kg

Increment:2.3 kg/inch

Over:10 in

Intermediate: 50.0 + 2.3 × 10 = 50.0 + 23

Result: IBW = 73.0 kg (~161 lbs)

Step 3

Compare with the other three formulas.

Hamwi: 48.0 + 2.7 × over | Robinson: 52 + 1.9 × over | Miller: 56.2 + 1.41 × over

Over:10 in

Intermediate: Hamwi 75.0 | Robinson 71.0 | Miller 70.3

Result: Average of four formulas ≈ 72.3 kg

Step 4

Cross-check against the healthy BMI range (18.5-24.9).

Range = 18.5 × H(m)² to 24.9 × H(m)²

Height:1.778 m

Intermediate: 18.5 × 3.16 = 58.5 | 24.9 × 3.16 = 78.8

Result: Healthy range: 58.5 - 78.8 kg

Final Answer

IBW ≈ 73 kg (Devine, 5'10" male) — healthy range 58.5-78.8 kg

Worked Examples

See how the calculator works with different scenarios.

Scenario

A 30-year-old man, 5 ft 10 in, checking the spread of the four classic formulas.

Inputs

Gender:Male

Height:5'10" (70 in)

Calculation

Hamwi: 48.0 + 2.7×10 = 75.0 | Devine: 50.0 + 2.3×10 = 73.0 | Robinson: 52 + 1.9×10 = 71.0 | Miller: 56.2 + 1.41×10 = 70.3 kg.

Result

IBW ≈ 70.3 - 75.0 kg (155-165 lbs) | Average ≈ 72.3 kg (159 lbs)

Interpretation

All four formulas cluster within about 10 lbs for average heights — the spread itself shows any single "ideal" number carries several pounds of uncertainty.

How Much Should I Weigh?

"Ideal weight" began as a medical dosing concept, not a beauty standard. The formulas that calculate it were built to estimate drug dosages from height and sex — and they remain genuinely useful in hospitals today. As personal targets, however, they carry real limits: no formula knows whether your weight is muscle or fat, how big your frame is, or how old you are.

The practical answer is a range, not a number: the WHO healthy BMI span (18.5-24.9) for your height, adjusted ±10% for frame size, interpreted alongside body fat percentage and waist circumference. Many perfectly healthy people — especially athletes — sit above every formula value.

The Four Formulas Side by Side

Formula (Year)	Men	Women
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

All values are per inch over 5 feet (60 inches) of height.

IBW in Modern Clinical Practice

Drug dosing — aminoglycosides, vancomycin, and anesthetic agents distribute in lean tissue, so IBW-based dosing prevents overdating in higher-fat patients and underdosing in lean ones.
Ventilator settings — lung-protective tidal volumes of 6-8 mL/kg are calculated from predicted body weight (a Devine derivative), a standard that measurably reduces lung injury in ARDS.
Kidney function — the Cockcroft-Gault creatinine clearance estimate uses IBW (or adjusted body weight) to avoid overstating clearance in obese patients.
Nutrition & bariatrics — hospital energy needs and surgical outcome metrics (%EWL) are referenced to IBW.

IBW vs Healthy Weight vs Your Ideal

Medically defined IBW is a single clinical reference from height and sex. BMI-based healthy weight is the evidence-based range for your height. Your personal ideal is whatever weight lets you perform, sleep, and live well — informed by both of the above plus body composition, not dictated by them.

Practical Tips

•Read all four formulas together: the average (or the cluster they form) is more informative than any single number.
•Use the healthy BMI weight range (18.5-24.9) as your realistic boundaries — it spans roughly 13-20% of body weight, far wider than the formulas' single points.
•Measure your wrist to estimate frame size: small frames sit near the bottom of the range, large frames near the top (classic ±10% adjustment).
•If you strength train seriously, expect to sit above your IBW at a healthy body fat percentage — that is normal, not a failure.
•Watch the height extremes: under 5'0" and over 6'3", formulas diverge sharply and BMI itself distorts; favor body composition measures.
•Do not chase the exact IBW number — treat it as a clinical reference point, with the BMI range and body fat percentage as better personal targets.
•Recalculate after any lasting height change (adolescents) or if using it for medical dosing conversations — always with your clinician's numbers.
•Combine with waist circumference: under 40 in (men) / 35 in (women) supports metabolic health regardless of the scale.
•For drug-dosing contexts (aminoglycosides, ventilator settings), clinical systems use adjusted or predicted body weight variants — defer to your care team.
•If your current weight differs greatly from IBW, set process goals (steps, protein, training sessions) rather than fixating on a target scale number.

Common Mistakes

Treating IBW as a health target

IBW formulas were built for drug dosing, not to define your best weight. They ignore muscle mass, frame, age, and ethnicity. Use them as a reference anchor alongside the healthy BMI range and body composition measures.

Picking one formula and ignoring the others

The four formulas can differ by 10-25 lbs at the same height. A single number hides that uncertainty. Compare all four — the calculator shows the full spread and average for this reason.

Applying IBW to muscular people

Formulas assume average muscle mass. Athletes routinely sit 15-30% above IBW at low body fat. Judge athletic bodies by body fat percentage and performance, not IBW.

Using IBW for children or teens

All four formulas apply to adults 18+. Growing bodies should be tracked on CDC BMI-for-age growth charts by a pediatrician — an adult IBW target during growth is inappropriate and potentially harmful.

Ignoring frame size

Bone structure shifts healthy weight by roughly ±10%. A large-wristed person at the formula number may be underweight; a small-framed person at the same number may be overfat. The wrist-based frame estimate adjusts for this.

Forgetting IBW's clinical purpose

IBW persists in medicine for dosing water-soluble drugs, setting ventilator tidal volumes (6-8 mL/kg IBW), and estimating kidney function (Cockcroft-Gault). Recreational use as a beauty standard is a modern misuse.

Comparing across formulas and sexes incorrectly

Female formulas have lower bases (45.5-53.1 kg at 5 ft) and mostly smaller increments. Comparing a woman's Devine to a man's Hamwi, or heights entered in the wrong unit, produces meaningless numbers.

Expecting formulas to include age

None of the four formulas contain an age term. The calculator collects age for context (and healthy-range interpretation) but the IBW numbers depend only on height and sex — age-related composition change is out of scope.

Assumptions

This calculator makes the following assumptions to provide estimates:

Adults 18+: All four formulas were developed on adult populations; pediatric use requires growth charts instead.

Average Body Composition: IBW assumes a typical muscle-to-fat ratio. Muscular, very lean, or sarcopenic individuals deviate systematically.

Heights Near Average: The linear per-inch design was fitted around average heights; under 5'0" and over 6'3" the spread widens and accuracy falls.

No Frame or Age Terms: The classic ±10% frame adjustment is optional (wrist-based here); the formulas themselves encode no age or ethnicity information.

Limitations

Be aware of these limitations when using this calculator:

Dosing Legacy: IBW was created for medication dosing — not aesthetics or health optimization — and should be interpreted in that spirit.

No Composition Data: IBW cannot distinguish muscle from fat; two people at their "ideal" can have completely different body compositions.

Narrow Height Validity: Linear extrapolation degrades at height extremes where real body proportions change faster than the per-inch increment.

Not Medical Advice: For actual clinical dosing or ventilator settings, your care team uses validated protocols — do not substitute this calculator.

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Authoritative References

Information sources used in creating this calculator and educational content.

Ideal Weight & Body Composition Glossary

Technical terms used in mortgage calculations explained in plain language.

Ideal Body Weight (IBW): A height- and sex-based reference weight developed for clinical dosing, computed by formulas like Devine and Hamwi as a base weight plus a per-inch increment.
Devine Formula (1974): Men: 50 kg + 2.3 kg per inch over 5 ft; women: 45.5 kg + 2.3 kg per inch. The most widely used clinical IBW equation.
Hamwi Formula (1964): Men: 48 kg + 2.7 kg per inch; women: 45.5 kg + 2.2 kg per inch. The earliest common IBW formula, with the largest male increment.
Robinson Formula (1983): Men: 52 kg + 1.9 kg per inch; women: 49 kg + 1.7 kg per inch. A recalibration of Devine producing lower values for taller people.
Miller Formula (1983): Men: 56.2 kg + 1.41 kg per inch; women: 53.1 kg + 1.36 kg per inch. The smallest increment — highest base, slowest growth.
Healthy Weight Range: The weight span corresponding to BMI 18.5-24.9 for a given height — the WHO-endorsed boundaries that frame any IBW number.
Frame Size: Small, medium, or large skeletal build, traditionally estimated from wrist circumference relative to height; shifts target weight about ±10%.
Adjusted Body Weight (ABW): A clinical variant — IBW + 0.4 × (actual − IBW) — used for dosing some medications in significantly obese patients.
Predicted Body Weight (PBW): A Devine-derived weight used to set ventilator tidal volumes (6-8 mL/kg) in critical care — the same formula, life-saving application.
%EWL (Percent Excess Weight Loss): Bariatric surgery outcome metric: weight lost divided by excess weight above IBW, making IBW the reference point for surgical success.

Frequently Asked Questions

Answers to common questions about this calculator.

What is ideal body weight (IBW)?

Ideal body weight is a height- and gender-based reference weight originally developed for medical drug dosing — not an aesthetic target. The common formulas (Hamwi, Devine, Robinson, Miller) all use a base weight at 5 feet plus a fixed increment per additional inch.

Which IBW formula is most accurate?

No formula is universally best. Devine is the most widely used in clinical practice. Robinson and Miller are 1983 recalibrations that yield lower values for taller people; Hamwi is the oldest with the largest male increment. Comparing all four — as this calculator does — is more informative than any single value.

What is the Devine formula?

Men: 50 kg + 2.3 kg per inch over 5 feet. Women: 45.5 kg + 2.3 kg per inch over 5 feet. Published by B.J. Devine in 1974 for medication dosing, it became the international clinical standard for IBW.

What is a healthy weight range?

The WHO healthy range corresponds to BMI 18.5-24.9. Unlike IBW formulas that produce a single number, the BMI-based range spans roughly 13-20% of body weight for any height, giving realistic upper and lower boundaries. This calculator shows it alongside the formulas.

Should I use IBW as my goal weight?

Not strictly. IBW ignores muscle mass, frame size, and body composition. Use it as a rough anchor alongside the healthy BMI range, body fat percentage, energy levels, and lab markers. Many healthy, fit people sit above their IBW.

Is IBW accurate for athletes or bodybuilders?

No. Muscular athletes commonly exceed IBW by 15-30% while carrying low body fat, because the formulas assume average muscle mass. Athletes should assess themselves via body fat percentage, lean mass, and performance rather than IBW.

How does frame size affect ideal weight?

Skeletal frame can shift a healthy weight by about ±10%: small-framed people sit toward the bottom of the healthy range, large-framed toward the top. Frame is traditionally estimated from wrist circumference relative to height — this calculator includes that option and applies the classic adjustment.

Can IBW formulas be used for children or teenagers?

No. The formulas apply to adults 18 and older. Children and teens should be assessed with CDC BMI-for-age percentile growth charts by a pediatrician, since healthy weight changes constantly during growth.

Why do doctors still use IBW?

IBW remains clinically central: aminoglycoside and vancomycin dosing, mechanical ventilator tidal volumes (6-8 mL per kg of predicted body weight), the Cockcroft-Gault kidney function estimate, and hospital nutrition assessments all key on IBW rather than total body weight.

What is adjusted body weight?

ABW = IBW + 0.4 × (actual weight − IBW). It approximates drug distribution volume in significantly obese patients for medications that penetrate lean tissue poorly, giving safer doses than either actual weight or raw IBW.

How is IBW used in bariatric surgery?

Excess weight is defined as actual weight minus IBW, and outcomes are reported as %EWL — percent excess weight lost. IBW therefore anchors both preoperative planning and long-term follow-up benchmarks.

Why do the four formulas give different answers?

Each was fit on different populations with different methods: Hamwi (1964) used the largest per-inch male increment (2.7 kg), Miller (1983) the smallest (1.41 kg). Divergence grows with height — under 5'6" they cluster; above 6'2" they can differ by 20+ lbs.

Does age affect IBW?

The formulas themselves contain no age term — they depend only on height and sex. Age does change body composition (muscle loss, height shrinkage), which is why older adults are often better served by the healthy BMI range plus body composition measures.

How is IBW different from BMI?

IBW outputs a single reference weight from height and sex via empirical formulas; BMI is an index computed from your actual weight and height, classified into ranges. IBW answers "what weight does the formula expect"; BMI answers "where are you now." They complement each other.

How much weight do I need to lose to reach my IBW?

The calculator computes the difference between your current weight and each formula result (and the healthy range). If the gap is large, target the healthy BMI range first — landing anywhere inside it is a legitimate success, not a failure to hit the formula number.

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Last Updated:

September 2026

Version:

2.0.0

References:

License:

Free to use. Results for educational purposes only, not medical advice.