Complete Guide to Ideal Body Weight
An ideal body weight (IBW) calculator gives a reference estimate of body weight based primarily on height, usually using a historical equation developed from population or clinical data. There is not one universally accepted "ideal" weight for every person. Different equations can produce different results at the same height because they were developed using different populations, assumptions, and mathematical relationships. A comparison of commonly used IBW equations demonstrates this variation clearly.
This calculator therefore shows several formulas rather than treating one number as an absolute answer. It calculates estimates from the Devine, Robinson, Miller, Hamwi, and Lemmens equations, then provides a consensus value based on the arithmetic mean of those five results.
The result is best interpreted as a reference point, not a diagnosis and not a prescription for what a person must weigh.
1. What Is Ideal Body Weight?
Ideal body weight is a historical term used for estimating a reference body weight from height. It has been particularly common in clinical and pharmacological settings because a simple height-based equation is easy to calculate when a patient's actual or appropriate dosing weight may not be directly usable. Several different equations have been published over the years, and they do not give identical results.
For example, at the same height, Devine, Robinson, Miller, and Hamwi can produce noticeably different estimates. That difference does not necessarily mean one calculation is "wrong"; it reflects the fact that the formulas were developed differently.
The practical implication is important:
An IBW number is a reference estimate, not a biological optimum that applies equally to everyone. Muscle mass, fat mass, body proportions, age, health status, and the reason the estimate is being used can all matter.
2. Why Does This Calculator Use Multiple IBW Formulas?
There is no single universally accepted ideal-body-weight equation. Published formulas vary in their coefficients and in the populations or reference tables from which they were derived. Reviews of IBW equations show substantial variation in the calculated result as height changes and as the selected equation changes.
This calculator addresses that problem by showing five approaches side by side:
| Formula | Main Basis |
|---|---|
| Devine (1974) | Height above or below the 5-foot reference |
| Robinson (1983) | Height-based regression-style actuarial reference |
| Miller (1983) | Updated height-based empirical equation |
| Hamwi (1964) | Height-based clinical dietetic reference |
| Lemmens (2005) | BMI 22.0 × height(m)² universal target |
The calculator's consensus IBW is the arithmetic mean of the five calculated values. That does not make the mean medically "more correct"; it simply provides a transparent central estimate across the selected formulas.
3. Devine Formula
The Devine equation was published in 1974 and became one of the most widely recognized IBW equations in clinical pharmacokinetics and medicine.
Men: IBW (kg) = 50.0 + 2.3 × (H - 60)
Women: IBW (kg) = 45.5 + 2.3 × (H - 60)
where H is height in inches and the resulting weight is in kilograms.
Example: For a 5-foot-10-inch male (H = 70 inches):
IBW = 50.0 + 2.3 × (70 - 60) = 50.0 + 23.0 = 73.0 kg (approx. 160.9 lb)
The Devine formula is historically important, but it should still be treated as a reference equation rather than an individualized health target.
4. Robinson Formula
The Robinson equation was published in 1983 as an actuarial revision of Devine using Metropolitan Life insurance data:
Men: IBW (kg) = 52.0 + 1.9 × (H - 60)
Women: IBW (kg) = 49.0 + 1.7 × (H - 60)
At 5 feet 10 inches, the male calculation is:
52.0 + 1.9 × 10 = 71.0 kg (approx. 156.5 lb)
This is lower than the Devine result for the same height, illustrating why comparing multiple formulas can be useful.
5. Miller Formula
The Miller equation is another commonly referenced height-based IBW equation:
Men: IBW (kg) = 56.2 + 1.41 × (H - 60)
Women: IBW (kg) = 53.1 + 1.36 × (H - 60)
For a 5-foot-10-inch male:
56.2 + 1.41 × 10 = 70.3 kg (approx. 155.0 lb)
6. Hamwi Formula
The Hamwi formula uses pounds directly and represents a historical height-based clinical reference:
Men: IBW (lb) = 106 + 6 × (H - 60) [approx. 48.0 kg + 2.7 kg/inch]
Women: IBW (lb) = 100 + 5 × (H - 60) [approx. 45.5 kg + 2.2 kg/inch]
For a 5-foot-10-inch male:
106 + 6 × 10 = 166 lb (or approx. 75.0 kg / 165.3 lb in metric conversion)
7. Lemmens Formula
The Lemmens approach takes a modern route away from piecewise "weight above 5 feet" linear equations:
The equation was proposed as a simple formula for both men and women, with the authors noting that the resulting value falls approximately midway within the range produced by several established IBW formulas.
For someone 1.778 m (5'10") tall:
IBW = 22.0 × (1.778)² ≈ 69.5 kg (approx. 153.2 lb)
Because the Lemmens method is mathematically based on BMI 22.0, it demonstrates an important connection between IBW calculations and BMI-based reference weights.
8. Why the Five Formulas Give Different Answers
Suppose a male is 5 feet 10 inches tall. This calculator's reference calculations produce approximately:
| Method | Estimated IBW |
|---|---|
| Devine | 160.9 lb (73.0 kg) |
| Robinson | 156.5 lb (71.0 kg) |
| Miller | 155.0 lb (70.3 kg) |
| Hamwi | 165.3 lb (75.0 kg) |
| Lemmens | 153.2 lb (69.5 kg) |
The spread is substantial enough to matter when interpreting the result. Research comparing IBW equations has found that calculated "ideal" weight varies between equations and can lead to different implied BMI values at the same height. That is precisely why this calculator displays individual formula results rather than hiding differences behind a single number.
9. Consensus Ideal Body Weight
The calculator's consensus value is calculated as the arithmetic mean of all five models:
For the reference case of a 28-year-old male at 5 feet 10 inches:
(160.9 + 156.5 + 155.0 + 165.3 + 153.2) ÷ 5 ≈ 158.3 lb (71.8 kg)
The consensus figure should be read as a mathematical summary of several reference equations, not as a clinically validated "perfect" weight.
10. WHO BMI-Based Healthy Weight Range
The calculator also shows a separate BMI-based reference range. For adults, the World Health Organization (WHO) classifies Body Mass Index as follows:
- Below 18.5: Underweight
- 18.5–24.9: Normal weight
- 25.0–29.9: Pre-obesity / Overweight
- 30.0 or higher: Obesity
The calculator converts the BMI reference limits into corresponding body weights:
Check your individual score on our dedicated BMI Calculator.
Important distinction:
The WHO BMI range and an IBW formula are not the same thing. An IBW formula asks: "What weight does this historical height-based equation estimate?" The BMI range asks: "What weight corresponds to the adult BMI reference range at this height?" Those are different calculations and should not be treated as interchangeable.
11. Does Bone Frame Size Change Ideal Body Weight?
Some historical clinical applications have used body-frame or anthropometric adjustments. This calculator allows an optional frame-size adjustment:
The frame adjustment is applied to the calculator's anthropometric IBW formulas. Frame size does not change the WHO BMI classification thresholds. Selecting a larger frame should never redefine a BMI of 25 as a "normal" BMI.
12. How Wrist Circumference and Frame Size Work
When automatic frame detection is enabled, the calculator uses wrist circumference together with biological sex and height to suggest a frame category. The calculator provides two distinct modes:
Automatic Mode
Wrist circumference is dynamically evaluated against validated anthropometric cutoffs to determine the calculated frame.
Manual Mode
Your selected Small, Medium, or Large frame is authoritative. Changing wrist circumference in manual mode does not overwrite your chosen frame.
13. Ideal Weight Is Not the Same as Healthy Weight
One of the most important limitations of IBW calculators is the word "ideal." A historical IBW formula does not know how much muscle you carry, where body fat is distributed, your physical activity, metabolic health, or nutritional status.
Two people can have exactly the same height and very different body compositions. A muscular athlete may weigh considerably more than an IBW estimate while maintaining a healthy body fat percentage. Compare your fat and lean mass distribution with our Body Fat Calculator.
14. How to Interpret Your Result
A useful way to read the calculator is to look at several numbers together:
- Individual formula estimates: See how much Devine, Robinson, Miller, Hamwi, and Lemmens differ.
- Consensus estimate: Use the calculator's arithmetic mean as a convenient central reference point.
- BMI-based range: Compare your current weight with the BMI-derived adult healthy reference range.
- Current-weight difference: The calculator shows how far your current weight is from the consensus estimate when provided.
- Frame-adjusted result: Understand frame adjustments as an anthropometric scenario rather than a change in underlying BMI classification.
15. Worked Example: 5'10" Male
• Age: 28 | Sex: Male
• Height: 5 ft 10 in (70 inches / 177.8 cm)
• Current Weight: 175 lb (79.4 kg)
• Wrist: 7.0 in | Frame: Medium
The difference between current weight and the consensus estimate is:
175 - 158.3 = 16.7 lb deficit
The calculator then shows illustrative planning timelines:
- 1.0 lb/week pace (approx. 500 kcal/day deficit): 17 weeks
- 1.5 lb/week pace (approx. 750 kcal/day deficit): 12 weeks
For daily energy and calorie planning, combine this target with our Calorie Calculator, TDEE Calculator, and BMR Calculator.
A Simple Way to Think About the Calculator
This diagram is intentionally simplified: IBW formulas and BMI are related through height, but they are not interchangeable measures.
Ideal Weight vs. BMI vs. Actual Healthy Weight
| Measure | What It Tells You |
|---|---|
| IBW | Historical height-based reference estimate |
| BMI Range | Population-based weight-to-height classification |
| Actual Healthy Target | Individualized clinical assessment incorporating health, blood markers, and body composition |
Frequently Asked Questions
Ideal body weight (IBW) is a historical reference estimate calculated primarily from height. Several different equations have been developed, including Devine, Robinson, Miller and Hamwi, and they can produce different answers for the same person. IBW should therefore be treated as a reference estimate rather than a universally correct target weight.
There is no single IBW formula that can be called universally most accurate for every person and every purpose. The published equations were developed using different methods and populations, and reviews show meaningful variation between them. This calculator displays five formulas so you can see the range rather than relying on one equation alone.
It depends on the formula. For example, the Devine male equation is 50 + 2.3 × the number of inches above 5 feet, with the result in kilograms. Robinson, Miller and Hamwi use different coefficients. The calculator calculates all supported formulas separately so their differences are visible.
Female IBW equations use coefficients that differ from the corresponding male equations. For example, the Devine female equation starts with 45.5 kg and adds 2.3 kg for each inch above 5 feet. Robinson, Miller and Hamwi use their own female coefficients.
Each equation was developed differently and uses different coefficients. Published comparisons show that the estimated IBW can vary substantially depending on the formula selected. That is normal and is one reason a multi-formula calculator is more informative than presenting one historical equation as the only answer.
The Lemmens equation is IBW = 22 × height(m)². It was proposed as a simple formula for both men and women, with the resulting value positioned approximately in the middle of values generated by several published IBW equations.
IBW is a collection of historical reference equations, while BMI is a weight-to-height index: BMI = kg/m². WHO uses BMI categories for adult population-level classification. An IBW value and a BMI-derived weight range can therefore be different without either calculation being mathematically wrong.
WHO classifies a BMI from 18.5 to 24.9 kg/m² as normal weight for adults. A BMI below 18.5 is classified as underweight, while 25.0–29.9 is pre-obesity/overweight and 30 or above is obesity.
No. Frame size may be used as an optional adjustment to some historical IBW calculations, but it does not change the mathematical BMI or the WHO BMI category thresholds. A larger skeletal frame should not be used to redefine a BMI of 25 as a normal BMI.
Yes. Historical IBW formulas are primarily height-based and do not directly measure muscle mass. A muscular person can weigh considerably more than an IBW estimate while having relatively low body fat. BMI has a similar limitation because it does not distinguish lean mass from fat mass.
No. An IBW calculation is only a reference estimate. A personally appropriate weight can depend on body composition, medical conditions, age, activity level, nutritional status and other factors that a height-based equation cannot capture.
The historical formulas can be calculated mathematically, but adult IBW and adult BMI interpretation should not simply be transferred to children. WHO uses age- and sex-specific growth references for people aged 0–19 rather than applying the adult BMI thresholds directly.
An IBW equation may appear in some clinical or pharmacological calculations, but the correct dosing weight is medication-specific. Some drugs may use actual body weight, ideal body weight, adjusted body weight or another dosing convention. Medication doses should therefore be determined using the appropriate clinical protocol rather than this calculator alone.
Not necessarily. The five equations can disagree by several pounds, and the result does not account for every aspect of health or body composition. It is better to use the calculator as a reference and consider your broader health context rather than treating the consensus value as a mandatory target.
They answer different questions. IBW formulas provide historical height-based reference estimates, while the WHO range converts adult BMI thresholds into an approximate weight range for a given height. Showing both helps users understand the difference between an IBW equation and a population-based BMI classification.
Clinical & Nutritional Disclaimer
This calculator is for educational and general planning purposes. Ideal body weight formulas are historical reference equations and do not provide an individualized medical diagnosis or universally appropriate target weight. BMI is a population-level screening measure and does not directly measure body fat or body composition. For children, pregnancy, eating disorders, significant medical conditions, medication dosing, or individualized weight-management decisions, use guidance from an appropriately qualified healthcare professional.