Ideal Weight Calculator
Estimate your ideal weight with four classic formulas
Ideal Weight by Formula
Healthy BMI Weight Range
Based on a healthy BMI of 18.5–25 for your height
Estimate an ideal body weight from four classic formulas at once, then compare them with the healthy weight range that BMI 18.5 to 25 implies for the same height. Enter a height in centimetres, choose male or female, and the calculator converts the height to inches, applies each formula’s 5 ft base, and returns four kilogram values plus a range. Because no single formula is authoritative, seeing all four side by side is more honest than trusting one number.
How to Use
- Type your height in centimetres. The tool accepts 100 to 250 cm, with one decimal place available.
- Select male or female. Each formula uses different base weights and per-inch increments.
- Press Calculate. The four formula results appear in a row, and the healthy BMI weight range appears below them.
- Compare the cluster of formula values against the BMI range rather than reading any single figure as a goal.
The Four Formulas and Their Constants
All four follow the same shape: a base weight at 5 ft (60 inches) plus a fixed increment for each additional inch. For heights below 5 ft, that same increment is subtracted.
| Formula | Male base and increment | Female base and increment |
|---|---|---|
| Devine (1974) | 50 kg + 2.3 kg/in | 45.5 kg + 2.3 kg/in |
| Robinson (1983) | 52 kg + 1.9 kg/in | 49 kg + 1.7 kg/in |
| Miller (1983) | 56.2 kg + 1.41 kg/in | 53.1 kg + 1.36 kg/in |
| Hamwi (1964) | 48 kg + 2.7 kg/in | 45.5 kg + 2.2 kg/in |
Devine was developed for calculating drug doses and remains the most widely cited. Robinson and Miller start higher and rise more slowly, so they flatten out at tall heights. Hamwi uses the largest per-inch increment for men, which makes it the steepest line of the four.
Worked Example: 175 cm Male
First the height is converted: 175 ÷ 2.54 = 68.90 inches, which is 8.90 inches above the 60-inch base. Applying each formula gives Devine 50 + 2.3×8.90 = 70.5 kg, Robinson 52 + 1.9×8.90 = 68.9 kg, Miller 56.2 + 1.41×8.90 = 68.7 kg, and Hamwi 48 + 2.7×8.90 = 72.0 kg. The four results span 68.7 to 72.0 kg. The height in metres squared is 1.75² = 3.0625, so the BMI range is 18.5×3.0625 = 56.7 kg to 25×3.0625 = 76.6 kg.
For comparison, a 160 cm female has 62.99 inches, or 2.99 inches above the base. Her results are Devine 52.4 kg, Robinson 54.1 kg, Miller 57.2 kg, and Hamwi 52.1 kg, with a BMI range of 47.4 to 64.0 kg.
How the Healthy BMI Range Is Calculated
The second output is independent of the four formulas. It multiplies the World Health Organization’s normal BMI bounds, 18.5 and 25, by your height in metres squared. For 175 cm that yields 56.7 to 76.6 kg. The lower figure is not a target to chase; it is the bottom of the band considered normal for that height. The range is wider than the formula cluster by design, because BMI is a screening measure across a population, not a clinical ideal for one person.
Why the Formulas Disagree
The formulas come from different eras, different source populations, and different study goals. Devine’s constants were chosen to make drug dosing convenient, not to describe an optimal weight. Robinson’s and Miller’s revisions pushed the base weight up and the slope down, producing different answers for tall people. Because the disagreement is largest at the extremes and at unusual heights, reporting a single result would hide the genuine uncertainty. A cluster such as 68.7 to 72.0 kg should be read as “roughly in this zone”, not “hit 70.5 exactly”.
Selecting a Reference Weight in Practice
If you need one number rather than four, pick the formula that matches the purpose. Devine is the safest default in a clinical or dosing context because it is the most widely recognised. Robinson and Miller tend to suit weight-management discussions at taller heights, where their flatter slopes avoid overstating the target. Hamwi is useful as an upper reference for men. A defensible approach is to use the median of the four as a central estimate and quote the range around it. For a 175 cm male, that median is 69.7 kg, sitting inside the 68.7 to 72.0 kg spread and comfortably below the BMI band’s 76.6 kg ceiling. Whatever you choose, compare like with like over time: switching formulas between measurements will manufacture apparent progress that is not real.
Limits and Scope
These are statistical references based only on height and sex. They do not account for muscle mass, bone density, frame size, age, or body-fat percentage, so muscular people may sit above every estimate while being perfectly healthy, and someone with a small frame may fit the lower end. The formulas were fitted to adults and are not appropriate for children or teenagers, who need growth charts, nor for pregnancy. Results are reported in kilograms and rounded to one decimal place. This calculator is informational and is not medical advice; for personal health decisions, especially around eating disorders, pregnancy, or illness, speak with a doctor or registered dietitian.
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Frequently Asked Questions
Which formula should I trust if the four results disagree?
None is authoritative. Devine is the most common in clinical dosing, Robinson and Miller were proposed as refinements, and Hamwi is older and rises fastest with height. Treat the four numbers as a range: the space between the lowest and highest is more informative than any single figure.
Why does the healthy BMI range not match the formula results?
The formulas are regression lines fitted to clinical and life-insurance populations, while the BMI range is a statistical band (BMI 18.5 to 25) applied to your height. The BMI band is usually wider, which is expected because it describes a population range rather than a single target.
My height is under 5 ft (152 cm) — is the result reliable?
Less so. Every formula adds or subtracts a fixed amount per inch away from a 5 ft base, so below that base the tool is extrapolating downward. The tool still accepts heights down to 100 cm, but the closer you get to that floor, the more those linear estimates should be treated as rough.
Should I recalculate after losing or gaining weight?
The formulas depend only on height and sex, so your target does not change when your current weight does. Recalculating is still useful as a reference point after weight changes, but the output will be identical unless you update the height or sex.
Do the formulas apply to children, athletes, or pregnant people?
No. They were derived from adult reference populations and assume a typical body composition. Children need age- and growth-based charts, athletes often exceed every estimate because of muscle mass, and pregnancy changes body composition entirely, so consult a clinician for those cases.
Why is the female Devine result so close to the Hamwi result?
Both for women start at 45.5 kg at 5 ft, and their per-inch increments are 2.3 kg and 2.2 kg. That makes them nearly parallel lines, so they stay within a kilogram of each other at ordinary heights. The male versions differ more because their bases and increments differ more.
Reviewed by the HandyTools Hub team · Last updated