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BMI Calculator
Body Mass Index with WHO classification and healthy weight range.
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Ideal Weight Calculator
Healthy weight range using Robinson, Miller and Hamwi formulas. No signup — your inputs stay in your browser.
Step By Step
How to Use This Calculator
4 steps
- Select your biological sex — the formulas use different baselines for male and female.
- Enter your height in cm, or switch to ft + in using the toggle.
- Three formula results (Robinson, Miller, Hamwi) and their average appear instantly.
- Use the average as a general reference, not a fixed target.
Worked Example
Example: Male, 175 cm (5 ft 9 in)
Use this sample to sanity-check your inputs and understand what the final result represents.
- 1Sex: Male · Height: 175 cm
- 2Robinson (1983): 52 + 1.9 × 9.06 in over 5 ft = 69.2 kg
- 3Miller (1983): 56.2 + 1.41 × 9.06 = 69.0 kg
- 4Hamwi (1964): 48 + 2.7 × 9.06 = 72.5 kg
Final Result
Average ≈ 70.2 kg (154.7 lbs) — a planning reference, not a fixed target.
Methodology
Robinson, Miller & Hamwi formulas
This section explains the calculation logic, assumptions, and source material used to make the result more trustworthy and easier to verify.
All three use inches above 5 ft (152.4 cm) as the variable (X). Robinson (1983): Male 52 + 1.9X; Female 49 + 1.7X. Miller (1983): Male 56.2 + 1.41X; Female 53.1 + 1.36X. Hamwi (1964): Male 48 + 2.7X; Female 45.5 + 2.2X. These were originally developed for clinical drug-dosing estimates, not fitness goals. A healthy weight for any individual also depends on muscle mass, bone density, age, and medical history.
Frequently Asked Questions
Why does this show three different results?+
Robinson (1983), Miller (1983), and Hamwi (1964) were each developed independently for clinical use — mainly to estimate drug dosing by body weight. They arrive at slightly different numbers because each researcher used a different study population. No single formula is universally 'correct', which is why the average gives a more balanced estimate.
What is ideal weight actually based on?+
These formulas estimate weight from height alone using a linear equation. They don't measure body fat, muscle mass, or bone density — so the result is a statistical midpoint, not a personal health target. Two people at the same height can have very different healthy weights depending on their build.
Is the result in kg or lbs?+
Both — the table shows kg and lbs side by side. The calculation runs in metric internally; the lbs column is converted automatically (1 kg = 2.20462 lbs).
Does sex affect the result?+
Yes. All three formulas use a lower baseline for females than males at the same height, reflecting average differences in skeletal frame and muscle mass between biological sexes.
Can I use this for children or teenagers?+
No — these formulas are designed for adults. For children and adolescents, healthy weight is assessed using age- and sex-specific growth charts (CDC or WHO). A paediatrician should interpret those results.
My BMI says I'm overweight but this says I'm fine — which is right?+
They measure different things. BMI is weight relative to height squared; ideal weight formulas are linear estimates. Neither accounts for body composition. If they conflict, the more useful step is talking to a doctor who can look at the full picture — waist circumference, blood work, activity level — rather than picking one number over the other.