Ideal Weight for Height: Why Different Formulas Give Different Answers
There isn’t one universal “ideal weight” for a given height. Doctors and researchers use different formulas—Devine, Robinson, Hamwi—and the healthy BMI range to estimate a target. Each formula was developed for different populations and purposes, so they yield slightly different numbers. Toolzo’s Ideal Weight Calculator shows all four at once, so you can see the range.
Why So Many Formulas?
The Devine formula was created in 1974 to calculate drug dosages. Robinson (1983) and Hamwi (1964) were also developed in clinical settings. They all use height above 5 feet as the variable, adding a certain weight per inch. For a 170 cm man, Devine gives 66 kg, Robinson 65 kg, and Hamwi 67 kg. The differences are small but highlight that “ideal” is a statistical concept, not a precise target. The healthy BMI range (18.5–24.9) adds another perspective, giving a weight range rather than a single number.
Step‑by‑Step: See Your Ideal Weight Range
- Open the Ideal Weight Calculator. Choose metric or imperial, enter your height and gender.
- Click “Calculate” to see a table with the results from Devine, Robinson, Hamwi, and the healthy BMI range (minimum and maximum weight).
- Use the BMI range as your primary guide, and the formula averages as supplementary targets.
BMI Range: The Broadest Guideline
BMI (Body Mass Index) is weight (kg) divided by height² (m²). A BMI of 18.5–24.9 is considered healthy for most adults. However, it doesn’t differentiate between fat and muscle. A bodybuilder might have a BMI over 25 but low body fat. Still, for the general population, the BMI range is a useful screening tool. Our calculator displays the exact weight range that corresponds to a healthy BMI for your height, giving you a flexible target.
Frequently Asked Questions
Which formula is most accurate?
No single formula is universally superior. The Hamwi formula is commonly used in clinical settings, while the BMI range is the most widely recognised public health measure.
Why do men and women have different ideal weights?
Formulas account for typical differences in lean body mass and body composition between sexes.
Should I aim for the lowest number?
Not necessarily. Being within the healthy BMI range and feeling energetic is more important than hitting a specific formula’s number.
Can teenagers use this calculator?
It’s designed for adults over 18. Children’s ideal weight is assessed using growth percentiles.
Is it free and private?
Yes, all data stays on your device.
Disclaimer: This is general information and not medical advice. Consult a healthcare professional for personalised weight goals.
Find Your Ideal Weight