Compare four historical ideal body weight equations for an adult height, review the full formula span, and place those estimates beside the weight interval corresponding to an adult BMI of 18.5 to 24.9. Results are references, not a prescribed target.
- Four published formulas
- Metric and US units
- Healthy-BMI reference interval
- Substituted calculation steps
Ideal Body Weight Calculator with Four Formulas
Enter an adult height and choose the historical male or female equation set. The calculator keeps Devine, Robinson, Miller and Hamwi results separate, then shows their span and simple average for comparison.
Historical equations for the male set at 175 cm
Formula comparison at the entered height
Male equation setMint bands show the adult BMI 18.5–24.9 weight interval at this height. Dots are formula estimates, not recommended targets.
Formula results
| Method | Estimate | Substituted equation |
|---|---|---|
| Devine | 70.5 kg | 50 + 2.3 × 8.8976 |
| Robinson | 68.9 kg | 52 + 1.9 × 8.8976 |
| Miller | 68.7 kg | 56.2 + 1.41 × 8.8976 |
| Hamwi | 72.3 kg | [106 + 6 × 8.8976] lb, converted to kg |
| Simple average | 70.1 kg | Arithmetic mean of the four estimates |
Height and reference breakdown
| Reference | Result | How to read it |
|---|---|---|
| Entered height | 175 cm | 68.8976 total inches |
| Distance from 5 ft | 8.8976 in above | Signed height value used by all four equations |
| Formula span | 68.7 to 72.3 kg | Lowest to highest historical estimate |
| Adult BMI reference | 56.7 to 76.3 kg | Weights at BMI 18.5 and 24.9 |
| Current weight | 70 kg | BMI 22.86; within the formula span |
Calculation steps
- Convert 175 cm to total inches: 175 ÷ 2.54 = 68.897638 in.
- Find signed inches from 5 ft: 68.897638 − 60 = 8.897638 in above 5 ft.
- Devine male estimate: 50 + 2.3 × 8.897638 = 70.464567 kg.
- The four unrounded estimates span 68.745669 to 72.296195 kg and average 70.102986 kg.
- At 1.75 m, BMI 18.5–24.9 corresponds to 56.65625–76.25625 kg.
Recent calculations
Results stay in this page session. Nothing is sent by this calculator.
How to Use This Ideal Weight Calculator
- Select the male or female coefficient set published with the historical formulas.
- Choose metric or US units, then enter adult height without shoes.
- Enter current weight only if you want a neutral comparison and current BMI. It does not change any formula estimate.
- Choose which reference appears in the headline. The complete comparison table remains visible.
- Select “Compare Weight Estimates.” Review the formula span, each separate estimate, the adult BMI reference interval and the substituted steps.
Measure height as accurately as practical. A one-inch change affects every classic formula and also changes a BMI-based weight interval because height is squared. Do not enter 5.8 for 5 ft 8 in. Enter 5 in the feet field and 8 in the additional-inches field.
What Does “Ideal Weight” Mean?
“Ideal body weight,” often shortened to IBW, is a historical reference-weight concept. It is not the one perfect weight for a body, and it does not account for muscle mass, bone structure, fat distribution, disability, health history, medicines, ethnicity, fitness, menopause or personal goals. The equations on this page use only height and one of two published coefficient sets.
The formulas became familiar in clinical settings because a quick height-based reference was useful for some calculations. Their origins are different from a modern, individualized assessment of health. This calculator therefore reports a span instead of silently choosing one formula as the answer. The simple average is shown for comparison, but averaging four historical equations does not create a medically validated target.
Ideal Body Weight Formulas
All four methods begin with a base value at 5 ft, or 60 in, then add a fixed amount for each inch above that point. This calculator represents the difference from 60 in as a signed number. A negative number below 5 ft produces a clearly labelled extrapolation, not a claim that the original equations were validated for shorter heights. Metric height is converted with exactly 2.54 cm per inch, and full precision is retained until display.
| Formula | Male equation | Female equation | Published context |
|---|---|---|---|
| Devine, 1974 | 50 kg + 2.3 kg × signed inches | 45.5 kg + 2.3 kg × signed inches | Introduced for a gentamicin dosing discussion |
| Robinson, 1983 | 52 kg + 1.9 kg × signed inches | 49 kg + 1.7 kg × signed inches | Regression from historical height-weight tables |
| Miller, 1983 | 56.2 kg + 1.41 kg × signed inches | 53.1 kg + 1.36 kg × signed inches | Analysis of Metropolitan height-weight tables |
| Hamwi | 106 lb + 6 lb × signed inches | 100 lb + 5 lb × signed inches | Older dietetic rule of thumb |
Hamwi is calculated in its common native pounds and then converted with 1 lb = 0.45359237 kg. This avoids drift caused by rounding its base and per-inch values into kilograms before calculation.
Worked Ideal Weight Example
For the male equation set at 175 cm, height is 175 ÷ 2.54 = 68.897638 in. The signed height difference is 68.897638 − 60 = 8.897638 in. The Devine result is 50 + 2.3 × 8.897638 = 70.464567 kg, displayed as 70.5 kg.
The same height gives approximately 68.9 kg with Robinson, 68.7 kg with Miller and 72.3 kg with Hamwi. The four-formula span is therefore 68.7 to 72.3 kg. Their unrounded arithmetic mean is about 70.1 kg. It is a comparison summary, not a fifth clinical formula.
Healthy BMI Range Versus Formula Estimates
The calculator also reverses the standard adult BMI equation at 18.5 and 24.9. CDC labels BMI 18.5 to below 25 as the healthy weight category for adults aged 20 and older. A weight at BMI 22 is displayed as a central mathematical reference because 22 sits inside that interval.
At 1.75 m, BMI 18.5 corresponds to about 56.7 kg and BMI 24.9 corresponds to about 76.3 kg. BMI 22 corresponds to about 67.4 kg. This interval is usually wider than the classic formula span because it represents a screening category, not a claim that every weight inside it has the same meaning for every adult.
BMI does not distinguish fat, muscle and bone, and it does not show where fat is stored. For individual health, CDC advises considering it with factors such as medical history, blood pressure, cholesterol, glucose and physical examination. The formula estimates have even fewer inputs, so they require at least as much caution.
Why the Four Formulas Give Different Results
Each equation uses a different base weight and per-inch increase. Devine began as an empirical clinical reference. Robinson and Miller used different versions of historical insurance height-weight tables. Hamwi uses rounded pound values. Because the slopes differ, the order of the estimates can change with height. Miller often gives a higher value near 5 ft because its base is larger, while Hamwi rises faster for taller male heights.
The formula comparison is useful because it makes this uncertainty visible. If two sites show different “ideal” weights, they may both be applying recognized equations correctly. Check the formula name, equation set, input units, height conversion and rounding before assuming one calculator has failed.
How Heights Below 5 Feet Are Handled
The published formulas are commonly worded as a base at 5 ft plus an amount for each inch over 5 ft. For a shorter height, this tool uses a negative signed height difference and subtracts each formula’s per-inch amount from its 5 ft base. It does not clamp the result to the 5 ft value. This is a transparent mathematical extension, not part of a validated personal-weight model.
A warning appears whenever height is below 5 ft. The result is labelled a linear extrapolation, not a validated short-stature target. Conditions that affect growth, spinal shape, measured standing height or body proportions need individualized assessment. The accepted technical range prevents obviously impossible inputs; it does not certify that every accepted height is suitable for the formulas.
Sex-Specific Coefficients and Their Limits
The original equations provide male and female coefficient sets. They do not ask for hormones, body composition or gender identity, and they do not publish a separately validated trans or nonbinary coefficient. The menu therefore says “equation set,” not that the calculator has determined anything about a person.
If neither historical set fits your clinical context, the tool cannot resolve the choice. A qualified clinician or dietitian can select an appropriate reference based on the purpose of the calculation. The BMI-based interval and BMI 22 reference do not use sex, but they still remain general screening mathematics.
Optional Current-Weight Comparison
Current weight is optional and never changes Devine, Robinson, Miller, Hamwi or BMI-reference calculations. When entered, the page reports current BMI and whether the number is below, inside or above the four-formula span. This is an arithmetic position statement, not a diagnosis or instruction to gain or lose the difference.
Body weight can change with hydration, food, clothing, menstrual cycle, edema, medicines and illness. A single scale reading does not explain the cause or establish a suitable goal. If you track weight, use the same reliable scale under similar conditions and focus on trends interpreted in context.
Formula Methods Compared
| Method | Inputs | Useful feature | Important limitation |
|---|---|---|---|
| Devine | Height and equation set | Widely recognized clinical reference | Not derived as a personalized wellness target |
| Robinson | Height and equation set | Based on regression from height-weight tables | Historical source population and tables |
| Miller | Height and equation set | Another independent comparison equation | Historical source data and low per-inch slope |
| Hamwi | Height and equation set | Simple native-pound rule | Rounded rule of thumb; frame adjustments are subjective |
| BMI 18.5–24.9 interval | Height | Standard adult screening reference | Does not measure body composition or personal health |
| BMI 22 reference | Height | Single sex-neutral mathematical comparison | One point inside a broad category, not an individual ideal |
Important Limits and Exceptions
Children and teenagers
Do not use these adult formulas for a child or teenager. People aged 2 through 19 require age- and sex-specific growth assessment, including BMI-for-age percentiles under the CDC framework. Adult fixed ranges begin at age 20.
Pregnancy and postpartum change
Do not use current pregnancy weight with this calculator. Pregnancy guidance uses pre-pregnancy BMI and pregnancy-specific weight-gain ranges. Postpartum recovery also needs individual timing, feeding and medical context.
Clinical treatment and medication dosing
Do not choose a medicine dose, ventilator setting, nutrition prescription or treatment from this public calculator. Some clinical protocols use ideal, predicted, adjusted, lean or actual body weight, and the correct choice varies by drug, procedure and patient. Confirm the required definition with the responsible clinician or pharmacist.
Body-composition and height exceptions
Amputation, edema, major fluid shifts, spinal curvature, inability to stand, unusually high muscularity, frailty and conditions that affect growth or body proportions can reduce the usefulness of a height-only equation. A clinician can select a more suitable measurement or reference.
How to Measure Height More Consistently
- Remove shoes, hats and bulky hair accessories.
- Stand on a firm, level floor with the measuring surface vertical.
- Keep heels together and stand as upright as comfortably possible.
- Keep the head level rather than looking sharply up or down.
- Lower a flat headpiece firmly onto the crown without compressing hair.
- Record the value before converting units and avoid early rounding.
- Use a professionally measured height when a clinical decision depends on it.
Common Ideal Weight Calculator Mistakes
- Calling one historical estimate a guaranteed healthy or attractive weight.
- Entering 5.8 ft when the intended height is 5 ft 8 in.
- Applying pound-based Hamwi constants as if they were kilograms.
- Rounding centimetres to whole inches before applying the formula.
- Assuming the four-formula average is clinically validated.
- Using adult formulas for children, teenagers or pregnancy.
- Using a public estimate for medication, nutrition or ventilator decisions.
- Treating current weight outside the formula span as a diagnosis.
Calculation Method and Review Sources
The origins, coefficients and limitations of Devine, Robinson and Miller were reviewed against Pai and Paloucek’s peer-reviewed history of ideal body weight equations. Devine’s adult equation and exact centimetre conversion were cross-checked against the CDC ideal body weight reference. Formula applicability, the Hamwi rule and caution at short or tall heights were also checked against the PENG professional statement on ideal body weight. The BMI 22 calculation was checked against the published height-squared reference equation.
The adult BMI category, screening purpose and individual limitations were reviewed against the current CDC BMI overview and adult BMI categories. Pregnancy cautions were checked against NIDDK pregnancy guidance. These sources support transparent calculations, not a personal target.
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Frequently Asked Questions
What is an ideal weight calculator?
An ideal weight calculator applies height-based reference equations such as Devine, Robinson, Miller or Hamwi. The word “ideal” is historical. The result is not a diagnosis or a personalized best weight.
Which ideal body weight formula is best?
No formula is best for every purpose or person. Each uses different historical coefficients. This page shows all four separately and reports their span so the method difference remains visible.
Why do Devine, Robinson, Miller and Hamwi give different results?
They use different base weights at 5 ft and different changes per additional inch. They also came from different empirical rules or historical height-weight tables, so correct calculations need not match.
How does the Devine formula calculate ideal body weight?
The male equation starts at 50 kg and the female equation at 45.5 kg for 5 ft, then adds 2.3 kg per inch above 5 ft. This calculator uses a signed difference below 5 ft and displays an extrapolation warning.
Is the healthy BMI weight range the same as ideal weight?
No. The BMI 18.5–24.9 interval is a broad adult screening category converted into weights at one height. Classic ideal-weight equations produce narrower single estimates and have different historical purposes.
What happens if height is below 5 feet?
The calculator subtracts each formula’s per-inch coefficient for the signed inches below 5 ft. It clearly labels the result as a mathematical extrapolation because the formulas are commonly published for inches over 5 ft and shorter-height validity is limited.
Does age affect the ideal weight formulas?
No. Devine, Robinson, Miller and Hamwi use height and a published male or female coefficient set. They do not adjust for age, which is one reason the result cannot be a complete personal health assessment.
Why does the calculator ask for a male or female equation set?
The source formulas publish two coefficient sets. They do not provide a separately validated nonbinary equation or account for hormones, body composition or gender identity. Select only when the historical set fits your purpose.
Can children, teenagers or pregnant people use this calculator?
No. This page is designed for non-pregnant adults aged 20 and older. Children and teens need growth-chart assessment, while pregnancy uses pre-pregnancy BMI and pregnancy-specific guidance.
Can I use this result for medication or clinical dosing?
No. Clinical protocols may require ideal, predicted, adjusted, lean or actual body weight depending on the drug and situation. Confirm the required equation and dose with the responsible clinician or pharmacist.
Health and Calculation Disclaimer
This calculator provides educational adult reference-weight estimates. It does not diagnose a condition, prescribe weight change, measure body composition or identify a universally healthy weight. Do not use it for children, teenagers, pregnancy, medication dosing, ventilator settings or nutrition treatment. Discuss weight, rapid change, eating concerns or medical decisions with a qualified health professional.