What is ideal body weight, and why are there so many formulas?
Ideal body weight (IBW) is a statistical reference: the weight that is typical or favorable for a given height. It did not start as a wellness goal. The earliest formulas were clinical shortcuts for dosing medicine and fluids. Body fat distorts how many drugs are distributed, so clinicians wanted a height-based reference weight that was independent of how much fat a particular patient carried. Only later did these numbers drift into diet culture as "target weights".
The formulas differ because they were written by different people, at different times, from different data. Hamwi (1964) is generally described as a rule of thumb from clinical nutrition practice, built on a base weight for a height of five feet plus a fixed amount for every additional inch. Devine (1974) is a simplified version widely used in drug dosing. Robinson and Miller (both 1983) are usually described as revisions with a gentler slope, so that very tall people are not assigned runaway values. (The coefficients here are the commonly published ones; they have not been re-checked against the original papers on this page.)
The five methods
All four classic formulas share one structure: a base weight at a height of 60 inches (about 152.4 cm), plus a fixed amount for each inch above that. Convert your height from centimeters to inches by dividing by 2.54, subtract 60, and plug the result in.
| Method | Men (kg) | Women (kg) |
|---|---|---|
| Devine | 50 + 2.3 Γ (inches β 60) | 45.5 + 2.3 Γ (inches β 60) |
| Robinson | 52 + 1.9 Γ (inches β 60) | 49 + 1.7 Γ (inches β 60) |
| Miller | 56.2 + 1.41 Γ (inches β 60) | 53.1 + 1.36 Γ (inches β 60) |
| Hamwi | 48 + 2.7 Γ (inches β 60) | 45.5 + 2.2 Γ (inches β 60) |
| BMI 22 weight | 22 Γ height(m)Β² (same for both sexes) | |
The BMI 22 method has a completely different structure. It solves for the weight at which BMI equals 22, with no inch conversion and no sex split. This calculator also shows the weight window that corresponds to the WHO normal BMI range of 18.5 to 24.9, the same range used by the BMI Calculator. A BMI of 22 sits near the middle of that window, but nothing says 22 is right for everybody.
Height-by-height comparison (calculated when the page is built)
The two tables below plug the formulas above into common heights. Values are in kilograms, rounded to one decimal. Notice how much the methods can disagree at the same height.
Men
| Height | Devine | Robinson | Miller | Hamwi | BMI 22 | BMI 18.5-24.9 |
|---|---|---|---|---|---|---|
| 150 cm | 47.8 | 50.2 | 54.9 | 45.4 | 49.5 | 41.6 - 56.0 |
| 155 cm | 52.4 | 53.9 | 57.6 | 50.8 | 52.9 | 44.4 - 59.8 |
| 160 cm | 56.9 | 57.7 | 60.4 | 56.1 | 56.3 | 47.4 - 63.7 |
| 165 cm | 61.4 | 61.4 | 63.2 | 61.4 | 59.9 | 50.4 - 67.8 |
| 170 cm | 65.9 | 65.2 | 66.0 | 66.7 | 63.6 | 53.5 - 72.0 |
| 175 cm | 70.5 | 68.9 | 68.7 | 72.0 | 67.4 | 56.7 - 76.3 |
| 180 cm | 75.0 | 72.6 | 71.5 | 77.3 | 71.3 | 59.9 - 80.7 |
| 185 cm | 79.5 | 76.4 | 74.3 | 82.7 | 75.3 | 63.3 - 85.2 |
| 190 cm | 84.0 | 80.1 | 77.1 | 88.0 | 79.4 | 66.8 - 89.9 |
Women
| Height | Devine | Robinson | Miller | Hamwi | BMI 22 | BMI 18.5-24.9 |
|---|---|---|---|---|---|---|
| 150 cm | 43.3 | 47.4 | 51.8 | 43.4 | 49.5 | 41.6 - 56.0 |
| 155 cm | 47.9 | 50.7 | 54.5 | 47.8 | 52.9 | 44.4 - 59.8 |
| 160 cm | 52.4 | 54.1 | 57.2 | 52.1 | 56.3 | 47.4 - 63.7 |
| 165 cm | 56.9 | 57.4 | 59.8 | 56.4 | 59.9 | 50.4 - 67.8 |
| 170 cm | 61.4 | 60.8 | 62.5 | 60.7 | 63.6 | 53.5 - 72.0 |
| 175 cm | 66.0 | 64.1 | 65.2 | 65.1 | 67.4 | 56.7 - 76.3 |
| 180 cm | 70.5 | 67.5 | 67.9 | 69.4 | 71.3 | 59.9 - 80.7 |
| 185 cm | 75.0 | 70.8 | 70.6 | 73.7 | 75.3 | 63.3 - 85.2 |
| 190 cm | 79.5 | 74.2 | 73.2 | 78.1 | 79.4 | 66.8 - 89.9 |
Two patterns stand out. First, the taller you are, the further the per-inch formulas drift from the BMI method; for a 190 cm man, Hamwi is well above the BMI 22 figure. Second, for shorter women (around 150 cm), Devine and Hamwi land close to the bottom of the normal BMI window, which is a reminder that these formulas were built for convenience in clinics and not as health targets for every body type.
Worked examples
Example 1: a man who is 170 cm tall. 170 Γ· 2.54 = 66.93 inches, which is 6.93 inches above 60. Devine = 50 + 2.3 Γ 6.93 = 65.9 kg (about 145 lb), Robinson = 52 + 1.9 Γ 6.93 = 65.2 kg, Miller = 56.2 + 1.41 Γ 6.93 = 66.0 kg, Hamwi = 48 + 2.7 Γ 6.93 = 66.7 kg. BMI 22 gives 22 Γ 1.7Β² = 22 Γ 2.89 = 63.6 kg, and the WHO normal window is 53.5 to 72.0 kg. The four formulas cluster within 1.5 kg, and BMI 22 sits about 2 to 3 kg lower.
Example 2: a woman who is 160 cm tall. 160 Γ· 2.54 = 62.99 inches, which is 2.99 inches above 60. Devine = 45.5 + 2.3 Γ 2.99 = 52.4 kg, Robinson = 49 + 1.7 Γ 2.99 = 54.1 kg, Miller = 53.1 + 1.36 Γ 2.99 = 57.2 kg, Hamwi = 45.5 + 2.2 Γ 2.99 = 52.1 kg. BMI 22 gives 22 Γ 1.6Β² = 56.3 kg, and the WHO window is 47.4 to 63.7 kg. Here the formulas spread across more than 5 kg (52.1 to 57.2), a good illustration of why a single figure is misleading.
Example 3: a man who is 180 cm tall. 180 cm is 70.87 inches, 10.87 above 60. Devine = 50 + 2.3 Γ 10.87 = 75.0 kg, Hamwi = 48 + 2.7 Γ 10.87 = 77.3 kg, and BMI 22 = 22 Γ 1.8Β² = 71.3 kg. Formulas with a steeper per-inch slope give larger values as height increases.
Which formula should you trust?
The practical answer is to trust the range, not any single figure.
- For a general sense of a healthy weight: start with the weight window for a BMI of 18.5 to 24.9. It is based on a population-level classification rather than a clinical dosing shortcut.
- If you want one reference point inside that window: use the BMI 22 weight, or the middle of the four classic formulas, and allow a few kilograms either side.
- When reading medical literature: "IBW" there almost always means a Devine-type formula used for dosing calculations. Do not equate that with a weight-loss goal.
Limits and common misunderstandings
- Muscle and fat are invisible to the formulas. A muscular person can weigh 5 to 10 kg more than the formula and still have low body fat, while someone at the formula weight can carry little muscle and a lot of fat. The Body Fat Calculator adds a second view.
- Age is ignored. With age, muscle tends to decline and fat share rises at the same weight. For older adults a somewhat higher weight is sometimes discussed as protective, so cutting down to the formula value is not necessarily a good idea.
- Height limits. The four classic formulas are anchored at about 152 cm. Below that they extrapolate downward and may undershoot; at very large heights they may overshoot.
- Population differences. The classic formulas come from Western clinical practice. Different regions use different BMI cut-offs, so a number from one tradition may not suit everyone as a health target.
- Ideal is not the same as best-looking or best-feeling. Within a healthy range, the weight at which you feel and perform best varies from person to person.
- Do not use this as a goal-setting tool if you are pregnant or breastfeeding, under 18, have a condition that causes fluid retention, or have a history of disordered eating. Young people should be assessed against growth charts instead.
How to use the result
- First check whether your current weight falls inside the WHO normal window. If it does, being a few kilograms off a formula value does not mean you need to lose weight.
- If you are outside the window, avoid aiming for the ideal weight in one go. A first milestone of about 5 percent of current body weight is easier to sustain. The right pace depends on your health, so ask your doctor.
- To plan intake, estimate maintenance calories with the BMR / TDEE Calculator or the Calorie Calculator, then adjust gradually. The Protein Intake Calculator helps with the protein side.
- Track more than the scale: waist measurement and body fat percentage help you tell fat loss from muscle gain.
Important notes
This calculator is a reference tool that produces a statistical estimate from height and sex alone. It does not diagnose, treat or prescribe. Your inputs are not sent to a server; the calculation runs in your browser. If you have a health concern or a medical condition that affects weight, talk to a doctor or dietitian.
Frequently Asked Questions
Is this result a good target weight for dieting?
It is a useful reference point but not an absolute target. Check the WHO normal window first, then look at body fat, waist size and how you feel within it. Talk to a professional if you have a medical condition.
Why do the formulas give different answers?
They were created at different times from different data, and they add a different amount for each extra inch of height. For men, Hamwi adds 2.7 kg per inch while Miller adds 1.41 kg, so the gap widens for taller people. That is why this page shows a range.
Why is the baseline weight different for men and women?
The research behind the formulas reflects that men on average carry more muscle and a larger frame, so the starting weight is higher. Differences between individuals of the same sex are larger than that average gap, so treat it as a rough adjustment. The BMI 22 method does not distinguish sex.
Can I trust the result if I am shorter than 152 cm?
The four formulas are built around a 60-inch baseline, so below about 152.4 cm they extrapolate and often give values that are too low. Rely more on the BMI-based figures in that case.
I have a lot of muscle and weigh far more than the formula. Is that a problem?
Weight alone cannot tell. Extra muscle makes you heavier than the formula value naturally. Look at body fat percentage, waist measurement and health check results such as blood pressure, glucose and lipids.
Why does the BMI 22 weight match the BMI calculator?
Both use weight = 22 Γ height in meters squared. This page simply adds the four classic formulas next to it, so the BMI-based numbers agree between the two pages.