CodeKitHubWhat Is This Tool?
An ideal weight calculator estimates the body weight statistically associated with good health for a given height and sex. The formulas it uses have a practical origin: Devine's 1974 formula was created for calculating drug doses, and Robinson (1983) and Miller (1983) are later refinements of it. Hamwi (1964) came from clinical nutrition practice. All four follow the same pattern — a base weight for 5 feet (152 cm) of height plus a fixed increment for every additional inch — which is why they agree closely at average heights and drift apart at the extremes.
The fifth method takes a different route: it inverts the BMI formula at a value of 21.7, the midpoint of the healthy BMI range of 18.5–25, giving the weight that puts you exactly in the middle of that range. Presenting all five as a range acknowledges what these formulas are — rough statistical conventions based on height alone. They know nothing about your muscle mass, bone structure or body composition, so treat the range as orientation, not as a target prescribed by medicine.
Why Use It?
- Compares four classic formulas — Devine, Robinson, Miller, Hamwi — plus the BMI 21.7 method in one calculation.
- Shows an honest range instead of pretending one exact number is 'your ideal weight'.
- Separate male and female coefficients, as defined in the original formulas.
- Accepts height in centimeters or feet and inches.
- Free and instant, with nothing uploaded — the calculation runs entirely in your browser.
How to Use
- Enter your height in centimeters, or switch to feet and inches.
- Select your sex — the classic formulas use different coefficients for men and women.
- Press the calculate button.
- Read the combined range at the top and the individual result of each formula in the table below.
Example
Input
Height 170 cm, maleOutput
Ideal weight range: about 62.7–68.4 kgDevine gives 66.1 kg, Robinson 65.3 kg, Miller 66.1 kg, Hamwi 66.9 kg and the BMI 21.7 method 62.7 kg. The spread of a few kilograms between formulas is normal — that is exactly why a range is more meaningful than any single value.
The five formulas at a glance
| Formula | Year and origin | Men | Women |
|---|---|---|---|
| Devine | 1974, drug dosing | 50 kg + 2.3 kg per inch over 5 ft | 45.5 kg + 2.3 kg per inch over 5 ft |
| Robinson | 1983, Devine refinement | 52 kg + 1.9 kg per inch over 5 ft | 49 kg + 1.7 kg per inch over 5 ft |
| Miller | 1983, Devine refinement | 56.2 kg + 1.41 kg per inch over 5 ft | 53.1 kg + 1.36 kg per inch over 5 ft |
| Hamwi | 1964, clinical nutrition | 48 kg + 2.7 kg per inch over 5 ft | 45.5 kg + 2.2 kg per inch over 5 ft |
| BMI 21.7 | Healthy-BMI midpoint | 21.7 × height² (m) | 21.7 × height² (m) |
How to read your result
- Treat the range as orientation: anywhere inside or near it is statistically unremarkable for your height.
- Cross-check with BMI — any weight that keeps your BMI between 18.5 and 25 is considered healthy, which is usually a wider band than the formula range.
- Muscular builds and athletes should expect to sit above the range; that is a formula limitation, not a health problem.
- Trends matter more than absolute numbers: stable weight, good energy and normal lab results outrank any formula.
- This calculator is a statistical estimate, not a medical diagnosis. For a real assessment of a healthy weight for you, talk to a doctor or dietitian.
Related health calculators
The BMI Calculator answers the reverse question — how your current weight rates for your height — and the Body Fat Calculator estimates the composition behind the number, which ideal-weight formulas cannot see.
To act on a weight goal, the Calorie Calculator estimates your daily intake target and the BMR Calculator shows the resting metabolism it is built on.
→ BMI Calculator · Body Fat Calculator · Calorie Calculator · BMR Calculator
Frequently Asked Questions
Why do the formulas give different results?
Because each was derived by different researchers, in different decades, for different purposes — Devine for drug dosing in 1974, Hamwi for clinical nutrition in 1964, Robinson and Miller as 1983 refinements. Each uses its own base weight and per-inch increment, so results diverge, especially for very short or very tall people. None of them is 'the correct one'; the spread between them is the honest picture, which is why this calculator reports a range.
What is the difference between ideal weight and BMI?
They are two views of the same question. BMI takes your actual weight and height and produces an index judged against the healthy band of 18.5–25. Ideal weight formulas work in reverse: from height alone they propose a target weight. The BMI 21.7 method in this calculator connects the two — it is simply the weight that lands you exactly mid-band. If your BMI is already within 18.5–25, you are in the healthy range regardless of what the classic formulas say.
Does the ideal weight account for muscle mass?
No — and this is the biggest limitation. All the formulas see is height and sex. Muscle is denser than fat, so a muscular person or athlete can sit well above the calculated range with low body fat and excellent health. Conversely, someone inside the range can carry too little muscle and too much fat. If you train seriously, a body fat measurement says far more than any height-based formula.
Should I diet to reach the calculated weight?
Not on the basis of this number alone. The range is a statistical orientation, not a medical prescription — it ignores age, body composition, health status and history. Sustainable weight goals should be set with a doctor or dietitian, who will look at far more than height. Rapid crash diets to hit a formula number are exactly the wrong takeaway.
Do these formulas work for children or during pregnancy?
No. All five methods were derived for adults of average build and are not valid for children, teenagers (who need growth-curve percentiles instead), pregnant women, or people at extreme heights, where the linear formulas drift furthest from reality. In those situations, ask a doctor rather than a formula.
Is my data stored anywhere?
No. The calculation runs in your browser with JavaScript; your height and sex are never sent to a server, stored or logged.