A walkthrough, end to end.
- 1
Pick metric (kg / cm) or imperial (lb / ft·in) units. Your inputs swap automatically — you don't have to convert anything by hand.
- 2
Enter your height and weight. Optional: add your age and sex for context — they're shown alongside the result but don't change the BMI value, which is the same formula for everyone.
- 3
Read your BMI on the gauge. The colored band shows whether you fall into Underweight, Healthy, Overweight or Obesity Class I/II/III using the World Health Organization adult ranges.
- 4
Use the Healthy Weight range as a target. The tool shows the kg and lb range that would keep your BMI between 18.5 and 24.9 at your current height.
How BMI is calculated
Body Mass Index is your weight in kilograms divided by your height in metres squared. Imperial units are converted to metric before the formula is applied. The result is a single number — the BMI — which is then placed inside one of the WHO adult bands.
What you can do with this.
BMI calculator for men
BMI is a height-weight ratio and uses the same WHO bands (18.5 / 25 / 30) for men and women — there is no separate ‘BMI for men’ formula. That said, men typically carry more lean mass than women at the same BMI, so the same number can mean a slightly leaner body composition. Treat the result as one signal, not the whole picture.
BMI calculator for women
The BMI formula and category bands are identical for women and men. Pregnancy, the postpartum period, and menopause-related changes can all push the number around in ways that don't reflect health — the calculator can't adjust for that, so use BMI alongside other context (waist measurement, energy levels, clinician input) when those apply.
BMI calculator for children and teens (2–19)
For ages 2 to 19, BMI is interpreted using sex-and-age-specific percentile charts (CDC in the US, WHO internationally), not the adult bands of 18.5 / 25 / 30. Enter the child's age and the calculator switches into a kid-mode result that explains the percentile-based categories — Underweight (<5th), Healthy (5th–85th), Overweight (85th–95th), Obesity (≥95th) — and links to the official CDC chart for the exact percentile.
BMI calculator for older adults (65+)
The standard WHO bands still apply at 65+, but a growing body of research suggests a slightly higher BMI (24–29) may actually be protective in older adults. Enter your age and the calculator surfaces a note about that research alongside the standard band — useful context for a conversation with a clinician.
BMI calculator 2026 — what's different
The formula and categories haven't changed for 2026 — BMI is still weight(kg) divided by height(m)². What has changed in clinical guidance is the recognition that BMI is one signal among several (waist-to-hip ratio, body composition, fitness markers all matter). The calculator reflects 2026 best practice by surfacing the limits of BMI right alongside the result.
Metric BMI calculator (kg / cm)
Switch to Metric and enter your height in centimeters and weight in kilograms. Most non-US health systems and most published BMI references use these units, so this is the default.
Imperial BMI calculator (lb / ft·in)
Switch to Imperial and enter feet, inches and pounds. The tool converts your inputs to metric internally and gives you the same BMI a clinician using metric would calculate.
Healthy weight range for your height
Beyond the BMI number, the result card shows the kg and lb range that corresponds to a healthy BMI (18.5 to 24.9) at your exact height. Useful as a target if you're tracking weight changes.
Quick BMI check before a doctor's visit
Some people like to know their BMI before an appointment so they can ask better questions. Calculate it here in two seconds; nothing leaves your browser, no account required.
Frequently asked.
BMI is a screening tool, not a diagnosis. It doesn't differentiate muscle from fat — so very muscular people can score in the 'overweight' range without being unhealthy, and people with low muscle mass can score 'healthy' while having too much body fat. It's also not appropriate for children, pregnant people, or the very elderly. Use it as one signal alongside other health metrics.
The WHO defines a healthy adult BMI as 18.5 to 24.9. Below 18.5 is classed as underweight; 25–29.9 is overweight; 30 and above is obesity (split into Class I, II and III as it climbs). These bands are population averages, not personal verdicts.
No. Every calculation runs in your browser using JavaScript. There is no server-side processing, no analytics on your inputs, and no cookies that store the values you type.
It shouldn't, except by tiny rounding. If you see a change, double-check the imperial inputs — feet and inches need to be entered separately, and 1 foot is 30.48 cm, so a small typo can shift the result a lot.
BMI overestimates body fat in muscular people because muscle is denser than fat. If you train heavily, treat your BMI as a rough number and lean on body fat percentage, waist-to-hip ratio, or DEXA scans for a clearer picture.
Not directly. Children and adolescents are scored against percentile charts that account for age and sex (CDC growth charts in the US, WHO charts internationally). The adult BMI bands used here would mislead you for anyone under about 18.