What should you weigh? It sounds like a simple question, but a single ‘ideal’ number rarely fits real bodies. Bone structure, muscle mass, age, and body composition all shift where your personal healthy weight sits — which is why experts talk about a healthy range rather than one magic figure. This ideal body weight calculator gives you that range, using long-established medical formulas plus a BMI-based cross-check.
The main figure comes from the Devine formula, created in the 1970s to guide medicine dosing and still widely referenced today. Alongside it, the tool shows the weight range that keeps your Body Mass Index between 18.5 and 24.9 — the band the World Health Organization classes as healthy for most adults.
Use the result as a reality check, not a verdict. If you are an athlete with heavy muscle, you may sit above the range while being perfectly fit, because muscle is denser than fat. If you are older or naturally slight-framed, the lower end may suit you better. It is a reference for reflection — or for a more informed chat with your doctor — not a target to chase at any cost.
Everything runs instantly in your browser: enter your height, pick a gender for the formula, and the range appears immediately. Nothing you type is uploaded or stored anywhere, so you can check privately any time.
How it works
The Devine formula works in inches: for men it is 50 kg plus 2.3 kg for every inch over five feet; for women it is 45.5 kg plus 2.3 kg per inch over five feet. So a man who is 170 cm tall (about 66.9 inches, or 6.9 inches over five feet) gets 50 + 2.3 × 6.9, roughly 65.9 kg. The formula is deliberately simple — it captures how height relates to healthy weight without accounting for build or muscle.
The second figure, the BMI-based range, comes from inverting the BMI equation. Since BMI equals weight in kilograms divided by height in metres squared, the healthy BMI band of 18.5 to 24.9 converts directly into a weight band. For that same 170 cm person, height squared is 2.89, giving a range of about 53.5 kg to 72.0 kg. Showing both lets you see where the two established methods agree.
Neither figure knows your frame or health history — which is why the tool shows ranges, not verdicts. Two people of identical height can both be healthy at quite different weights — the formulas describe population averages, and you are an individual.
How to use this tool
- Enter your height in centimetres.
- Select your gender, since the Devine formula differs slightly for men and women.
- Click Calculate to see your ideal weight and healthy range in kilograms.
- Compare the Devine figure with the BMI-based range shown alongside it.
- Factor in your build, muscle mass, and age when interpreting the numbers.
- Use the range as a reference point, not a strict target to hit.
Practical tips
- Think in ranges, not single numbers: landing anywhere inside the healthy band is a good outcome, and chasing an exact figure causes needless stress.
- If you lift weights or play sport, pay more attention to waist measurement and how you feel than to the scale — muscle weighs more than fat.
- Recheck after big life changes — new training, injury, or simply ageing can legitimately move your healthy range.
- Pair the number with steady habits — sleep, movement, balanced meals — rather than crash diets, which rarely work long-term.
Frequently asked questions
Which formula does this calculator use?
It uses the Devine formula, originally developed for medicine dosing in the 1970s, and cross-checks the result with the BMI-based healthy range of 18.5 to 24.9. Devine gives a single reference weight from your height and gender; the BMI band gives a range. Together they give a more balanced picture than either method could offer alone.
Why a range instead of one ideal number?
Because healthy bodies vary. Frame size, muscle mass, age, and body composition all shift where your personal healthy weight sits. A single number pretends at precision the science does not support, while a range acknowledges that several nearby weights can all be perfectly healthy for the same height. Aim to land comfortably inside the band rather than chasing one exact figure.
I exercise a lot and weigh more than the range. Is that bad?
Not necessarily. Muscle is denser than fat, so muscular people often weigh above height-based ranges while having low body fat and excellent fitness. These formulas cannot tell muscle from fat. If you train regularly, waist circumference, strength, stamina, and how you feel are far better guides than the scale alone.
How is this different from BMI?
BMI divides your weight by your height squared and sorts you into categories like underweight, normal, or overweight. Ideal weight formulas work the other way: they start from height and suggest what weight would be typical. This tool shows both, because each catches something the other misses — but both are population averages, not personal diagnoses.
Does age change my ideal weight?
Modestly. People often gain a little weight with age as muscle mass declines and metabolism slows, and a slightly higher weight can even be protective in older adults. The formulas do not adjust for age, so treat the range as a guide and discuss personal targets with your doctor, especially after 60.
Can I use this for children or teenagers?
No — these formulas are designed for adults only. Children's healthy weight is assessed with age- and gender-specific growth charts, not with adult formulas. If you are concerned about a child's weight, a paediatrician is the right person to ask. Growth charts account for development stages that adult equations simply ignore.
Note: This is a general reference, not medical advice; body composition matters — consult a health professional for personal weight guidance.