Ideal Weight Calculator
Compare four widely used “ideal body weight” formulas and the general adult BMI reference range for your height, so you can see how they differ rather than relying on one figure.
How Your Current Weight Compares
Formula Reference
Ideal Weight Calculator — Compare Multiple Formulas
Our Ideal Weight Calculator shows you four commonly used “ideal body weight” formulas — Devine, Robinson, Miller and Hamwi — alongside the general BMI reference range for adults, all side by side. Rather than presenting one number as “the answer,” this tool is built to show you how much these formulas actually disagree with each other, because there is no single scientifically agreed ideal weight for any given person.
Why Are There Multiple “Ideal Weight” Formulas?
Each formula below was developed at a different time, for a different original purpose, using different reference populations. None of them were designed as a universal target that everyone should aim for:
- Devine formula (1974): Published in the context of ideal body-weight estimation for drug-dosing calculations. It was subsequently adopted more broadly as a general “ideal weight” reference, largely by convention rather than because it was validated as a general population target.
- Robinson formula (1983): Another ideal body-weight equation developed for drug-dosing calculations, using different constants from Devine.
- Miller formula (1983): Another variation using different constants to estimate ideal body weight.
- Hamwi formula (1964): One of the earliest and simplest formulas, originally developed as a quick clinical rule of thumb rather than a precise calculation.
Because each formula uses different constants, they can disagree by several kilograms for the same height and sex — which is exactly why we show all four together rather than picking one.
How Are These Formulas Calculated?
All four formulas follow the same basic pattern: a base weight for 5 feet (152.4cm) in height, plus an additional amount for every inch above 5 feet. They differ in their starting base weight and their per-inch increment, and each formula uses different constants for men and women. Because 5 feet is used as the reference height in all four formulas, estimates for people below 5 feet fall outside the range these formulas were built around and should be interpreted cautiously rather than taken at face value.
| Formula | Men | Women |
|---|---|---|
| Devine (1974) | 50 kg + 2.3 kg per inch over 5ft | 45.5 kg + 2.3 kg per inch over 5ft |
| Robinson (1983) | 52 kg + 1.9 kg per inch over 5ft | 49 kg + 1.7 kg per inch over 5ft |
| Miller (1983) | 56.2 kg + 1.41 kg per inch over 5ft | 53.1 kg + 1.36 kg per inch over 5ft |
| Hamwi (1964) | 48.0 kg + 2.7 kg per inch over 5ft | 45.5 kg + 2.2 kg per inch over 5ft |
We also calculate the general BMI reference range for your height (a BMI of 18.5 to 24.9). This is the general reference range commonly used for adults, not a target that applies universally to everyone — it doesn’t account for muscle mass, frame size, age, ethnicity or other individual factors, so we show it as a range for context rather than a single-point estimate.
How to Use This Calculator
- Choose your units — metric (kg/cm) or imperial (lb/ft-in).
- Select your sex, since each formula uses different constants for men and women.
- Enter your height.
- Optionally enter your current weight to see how it compares with each estimate — this is entirely optional, and the calculator works without it.
- Review the four formula estimates and the general BMI reference range together, rather than focusing on any single number.
Limitations of “Ideal Weight” Formulas
- None of these formulas account for muscle mass, bone density or frame size. A muscular, athletic person will often weigh more than these formulas suggest without carrying excess fat.
- They were developed decades ago on specific reference populations and may not generalise well to everyone.
- They aren’t intended for children, adolescents, or pregnant or breastfeeding women.
- They only use height and sex — they don’t take into account age, activity level, health conditions, or ethnicity, all of which can influence what a healthy weight looks like for a given individual.
- All four formulas use 5 feet as their reference height, so estimates for people below that height should be interpreted cautiously.
- BMI, used for the general reference range shown here, has similar limitations: it doesn’t distinguish between fat and muscle, and can be less reliable for very muscular or very lean people.
These figures are best used as general reference points for conversation with a healthcare professional, not as personal targets to aim for on their own.
Frequently Asked Questions
What is an “ideal weight” calculator and how does it work?
It’s a tool that applies historical reference formulas — based on your height and sex — to estimate a body weight that was originally used as a clinical or statistical reference point. This calculator deliberately shows several different formulas together, since none of them is a single definitive answer.
Why do different formulas give different results?
Each formula was developed independently, using different reference populations and different constants for the relationship between height and weight. Devine, Robinson, Miller and Hamwi can each produce noticeably different estimates for exactly the same height, which is why comparing them side by side is more informative than relying on just one.
Which ideal weight formula is most accurate?
There isn’t a formula that’s been established as universally “most accurate” — each was developed for a different purpose and population. The Devine formula is the most widely cited today, largely because it became a convention in clinical drug-dosing calculations, but that doesn’t make it more correct as a general target than the others.
Does ideal weight account for muscle mass?
No. These formulas are based only on height and sex, so they don’t distinguish between muscle, fat, or bone. A muscular or athletic person may weigh more than these formulas suggest without that reflecting excess body fat.
Is BMI a good measure of ideal weight?
BMI is a widely used screening tool that relates weight to height, and the general BMI reference range (18.5–24.9) is included here for context. This range is the general reference commonly used for adults, not a value that applies universally to everyone. BMI doesn’t distinguish between muscle and fat and can be less reliable for very muscular or very lean individuals, so it’s best treated as one data point rather than a definitive measure.
Do these formulas work for children or during pregnancy?
No. All four formulas were developed for adults and don’t apply to children, adolescents, or pregnant or breastfeeding women, whose healthy weight ranges are assessed differently by healthcare professionals.
What if my weight is outside the general BMI reference range but I’m otherwise healthy?
Weight is only one indicator among many, and factors like muscle mass, fitness, diet quality and overall health matter too. If you have questions about your own weight or health, a GP or registered dietitian can give you personalised guidance that takes your individual circumstances into account, rather than relying on a general formula.
How was the Devine formula originally used?
The Devine formula was published in 1974 in the context of ideal body-weight estimation for drug-dosing calculations. It was subsequently adopted more broadly as a general ideal-weight reference.