BMI calculator — body mass index with healthy weight range
Calculate an adult BMI from height and weight, using metric or imperial measurements. See the screening category and the weight range corresponding to BMI 18.5–24.9 at that height.
Runs in your browser — your input is not uploaded to ToolsNow.
BMI compares adult weight with height. It does not measure body fat or diagnose health. Build, age and where fat is carried also matter.
These adult categories are not suitable for children or pregnancy. Ask a clinician if you need help interpreting your result.
How to use
- Choose your units. Use kilograms and centimetres, or pounds and feet/inches. Enter 175 for a height of 1.75 metres in metric mode.
- Enter height and weight. For example, 70 kg and 175 cm gives a BMI of 22.9.
- Read the category in context. The category describes weight relative to height. The displayed weight range is a reference band, not a personal target.
Questions
What does the weight range mean?
It is the weight corresponding to BMI values of 18.5 and 24.9 at the entered height. At 175 cm, that is about 56.7–76.3 kg. The label “Healthy range” refers to this screening band; it does not establish whether a particular weight is healthy for an individual.
Which BMI categories are shown?
The calculator uses below 18.5 for underweight, 18.5 to below 25 for healthy weight, 25 to below 30 for overweight, and 30 or above for obesity. It divides the last group into classes at 35 and 40. The category uses the unrounded BMI, while the number on screen is rounded to one decimal place.
Can this assess a child’s growth or body fat?
No. Children and teenagers need age-specific assessment rather than these adult bands. BMI also cannot distinguish muscle from fat or account for pregnancy, body composition or individual medical circumstances.
How can I check the calculation?
Divide weight in kilograms by height in metres squared: 70 ÷ (1.75 × 1.75) ≈ 22.86, displayed as 22.9. Imperial entries are converted to metric before calculating.
How it works and sources
How this is calculated
BMI is weight in kilograms divided by height in metres squared. The tool uses adult screening bands: below 18.5, underweight; 18.5 to below 25, healthy weight; 25 to below 30, overweight; and 30 or above, obesity. The weight range shown alongside it is calculated from BMI values of 18.5 and 24.9.
What the calculation assumes
- These are adult reference bands. Children and teenagers need an age- and sex-specific assessment; this tool does not provide one.
- The calculation uses the height and weight you enter. It does not ask your age or check whether adult BMI is appropriate for you.
Where the result has limits
- BMI does not distinguish muscle from fat or show where body fat is carried. The same BMI can mean different things for different people.
- Pregnancy, body composition and medical circumstances can make these bands unsuitable. They are not a pregnancy weight guide.
- The WHO link supports the general adult classification. It does not establish a personal target or cover every population-specific assessment.
- The displayed BMI is rounded, while the category uses the unrounded value. A number near a boundary can therefore look inconsistent with its label.
Sources
- A healthy lifestyle — WHO recommendations (BMI classification) World Health Organization
Sources last checked 30 July 2026.
These estimates are general information, not medical advice.
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