Ideal Weight Calculator
Enter your height and sex to see an ideal body weight estimate from two published formulas. The guide below explains how each formula works and when to treat the answer with caution.
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Created by the Reeliy Editorial Team. Last updated: Oct 19, 2026
What ideal body weight means
Ideal body weight (IBW) is a reference figure for the weight that goes with a given height. It was never meant as a personal goal. The first formulas were written by clinicians who needed a quick, repeatable number to scale drug doses and fluid volumes to body size, and the idea later spread to general health websites.
Because the figure depends on height and sex only, it ignores bone structure, muscle, age and where you carry fat. Treat it as one point of reference rather than a verdict. For a range instead of a single number, compare it with the healthy band from the healthy weight calculator or check your BMI.
How to use the calculator
- Choose US units to type feet and inches, or Metric units to type centimetres (or metres, using the drop-down beside the box).
- Enter your height. A blank height is read as zero, so fill the box in before you press Calculate.
- Pick male or female. This changes the Devine result only; the Peterson formula gives one answer for both sexes.
- Read the two results. They are shown in pounds for US units and kilograms for metric units, rounded to one decimal place.
The tool is designed for adults. It applies the formulas literally, so very short heights return negative weights. That is a sign the formulas are being stretched beyond the range they were built for, not a calculation error.
The two formulas
Both formulas below return kilograms. The calculator converts to pounds with 1 kg = 2.20462 lb when you choose US units.
Peterson formula
Peterson and colleagues published an equation in 2016 that links weight, height and BMI in a single expression. Fixing the BMI at 22, a value near the middle of the normal range, gives the ideal weight for any height:
IBW = 2.2 × 22 + 3.5 × 22 × (height in m − 1.5) = 48.4 + 77 × (height in m − 1.5)At 1.50 m the result is 48.4 kg; each extra centimetre adds 0.77 kg.
Devine formula
B. J. Devine proposed his equation in 1974 to help with drug dosing. In its original imperial form it starts from 50 kg for a man (45.5 kg for a woman) at five feet and adds 2.3 kg for every inch above that. The calculator uses the equivalent metric form with 152 cm as the starting height:
men: IBW = 50 + 0.9 × (height in cm − 152)
women: IBW = 45.5 + 0.9 × (height in cm − 152)
Hospitals use close relatives of this equation when they set ventilator volumes, because lung size follows height and sex rather than actual body weight.
Worked examples
A man who is 175 cm tall. Peterson: 48.4 + 77 × (1.75 − 1.5) = 48.4 + 19.25 = 67.65 kg, shown as 67.7 kg (149.1 lb). Devine: 50 + 0.9 × (175 − 152) = 50 + 20.7 = 70.7 kg (155.9 lb). The two formulas land about 3 kg apart.
A woman who is 5 ft 6 in tall. The height is 66 in × 2.54 = 167.64 cm = 1.6764 m. Peterson: 48.4 + 77 × 0.1764 = 61.98 kg, which is 136.6 lb. Devine: 45.5 + 0.9 × (167.64 − 152) = 59.58 kg, which is 131.3 lb. Here Devine gives the lower figure because the starting weight for women is 4.5 kg below the men's.
Ideal weight by height
The table shows the calculator's results in kilograms for common adult heights, so you can see how the formulas diverge as height increases.
| Height | Peterson (both sexes) | Devine, men | Devine, women |
|---|---|---|---|
| 150 cm (4 ft 11 in) | 48.4 kg | 48.2 kg | 43.7 kg |
| 160 cm (5 ft 3 in) | 56.1 kg | 57.2 kg | 52.7 kg |
| 170 cm (5 ft 7 in) | 63.8 kg | 66.2 kg | 61.7 kg |
| 180 cm (5 ft 11 in) | 71.5 kg | 75.2 kg | 70.7 kg |
| 190 cm (6 ft 3 in) | 79.2 kg | 84.2 kg | 79.7 kg |
Peterson rises by 0.77 kg per centimetre and Devine by 0.9 kg, so for taller people the Devine figure runs further ahead. Between 150 and 160 cm the two are within about a kilogram of each other for men.
Limits of an ideal weight figure
- Muscle is invisible to the formula. A trained athlete can weigh well above the figure and be lean, and a sedentary person at the figure can still carry a high share of body fat. A body fat estimate adds the missing detail.
- Age and frame size are ignored. Older adults tend to carry a little more weight in good health, and a broad frame supports more mass than a slight one at the same height.
- Single numbers hide wide ranges. Population studies find the lowest health risk across a band of weights, not at one point.
- Short and very tall heights are extrapolations. Both formulas were fitted in the adult height range, so results for heights below about 150 cm or above 200 cm are less reliable.
These results are estimates for informational use and are not medical advice. Talk to a doctor or dietitian before you set a weight goal. See our disclaimer.
Turning a number into a plan
If your current weight is far from the figure, the useful question is how fast and by what means to move toward a healthy range. The weight loss calorie calculator estimates the daily energy intake for a chosen pace, and the water intake calculator helps you plan hydration as your activity changes.
Frequently asked questions
Why do the Peterson and Devine results differ?
They use different starting points and slopes. Peterson assumes a BMI of 22 at every height and adds 0.77 kg per centimetre, while Devine starts from 50 kg for men or 45.5 kg for women at 152 cm and adds 0.9 kg per centimetre. The gap is small near average heights and grows for taller people.
Does the Peterson formula depend on sex?
No. The equation uses only height and a fixed BMI of 22, so men and women of the same height get the same answer. Devine is the one that separates the sexes.
Is my ideal weight the same as a healthy weight?
Not exactly. An ideal weight is a single reference value from a formula, while a healthy weight is usually a range, often defined as a BMI between 18.5 and 24.9. Anywhere in that range can be healthy for you.
Why does the calculator show a negative weight for a very short height?
The formulas are straight lines that were fitted to adult heights. Extend them far enough below that range and they cross zero, so the output is meaningless there. Use adult heights only.
References
- Peterson CM, Thomas DM, Blackburn GL, Heymsfield SB (2016). Universal equation for estimating ideal body weight and body weight at any BMI. American Journal of Clinical Nutrition 103(5):1197-1203.
- Devine BJ (1974). Gentamicin therapy. Drug Intelligence and Clinical Pharmacy 8:650-655.
Cite this calculator and page
If you use this page in your work, you can cite it as:
Reeliy Editorial Team. (2026). Ideal Weight Calculator. Reeliy. https://reeliy.com/calculators/ideal-weight-calculator“Ideal Weight Calculator.” Reeliy, 2026, https://reeliy.com/calculators/ideal-weight-calculator.