BMI Calculator
Body Mass Index calculator with metric and imperial support, plus health category.
About BMI Calculator
The BMI Calculator computes your Body Mass Index from height and weight — in metric or imperial units — and shows your category (underweight, healthy, overweight, obese) using standard WHO ranges, along with the healthy weight range for your height.
BMI is weight in kilograms divided by height in metres squared. Because it uses only two measurements, it is useful for broad adult screening and population comparisons but cannot distinguish body fat, muscle, bone mass or fat distribution.
Your measurements are processed in your browser and never leave your device. Treat the category label as a starting conversation point with a clinician, not as a diagnosis or a substitute for waist, fitness, blood markers and medical history.
If you are tracking weight over time, log the same unit system each session and note clothing or timing differences. Small day-to-day swings are normal; the healthy range for your height is more useful as a band than as a single target number.
How BMI Calculator works in practice
- 1Choose your unit system: metric (cm/kg) or imperial (ft-in/lb).
- 2Enter your height and weight.
- 3Read your BMI, category and the healthy weight range for your height.
- 4Adjust inputs to see how a target weight would change the result.
Jobs this tool is built for
- Calculate an adult BMI before a routine wellness discussion with a clinician.
- Convert imperial height and weight into the same screening value used by metric charts.
- See the weight interval corresponding to the standard healthy BMI range for a height.
- Track a broad weight trend while also monitoring waist, fitness and other health indicators.
What you can do here
- Metric and imperial input
- Standard WHO categories
- Healthy weight range for your height
- Local calculation — measurements are not uploaded
Limits and honest caveats
- BMI is a screening measure, not a diagnosis. Athletes with high muscle mass can score "overweight" while being very fit.
- This calculator uses adult ranges — children need paediatric percentile charts, which it does not implement.
- Pregnancy, certain medical conditions and age-related body composition changes need professional interpretation beyond BMI alone.
How the result is produced
BMI is weight divided by height squared. This page uses the adult WHO bands and does not diagnose anything.
- 1.Convert height to metres. 170 cm is 1.70 m.
- 2.Divide weight in kilograms by height squared: BMI = kg / m².
- 3.Place the number in a WHO adult band: under 18.5, 18.5–24.9, 25–29.9, or 30 and above.
- 4.Treat the band as a screening label. Muscle, pregnancy, and childhood growth change what the same number means.
Worked example: 70 kg at 170 cm
Height 1.70 m squared is 2.89. 70 ÷ 2.89 is about 24.2, which sits inside the WHO adult range of 18.5–24.9. The same 70 kg at 160 cm (height squared 2.56) is about 27.3, which the same bands label overweight. Neither result is a medical diagnosis.
Common questions about BMI Calculator
What BMI is considered healthy?
For adults, the WHO considers 18.5–24.9 a healthy range.
Should I rely only on BMI?
No — combine it with waist circumference, blood pressure, cholesterol and lifestyle factors, ideally with a doctor.
Why can an athlete have a high BMI?
BMI counts all body mass alike. Extra muscle can raise weight without indicating the same health risk as excess body fat.
Is this calculator suitable during pregnancy or for children?
No. Pregnancy changes normal weight interpretation, and children require age- and sex-specific growth percentiles. Seek appropriate clinical guidance.
This page was written by the ToolSink team to explain how BMI Calculator works on this site — it is not syndicated, scraped, or spun from another publisher. How we write tool guides · Site updates · About ToolSink.
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