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Health calculator

BMI Calculator

Calculate your Body Mass Index from height and weight, in metric or imperial units.

BMI is a quick screening number used by health professionals to flag potential weight concerns. Enter your height and weight below, choose your unit system, and the calculator returns your BMI score and category. Your data stays in your browser — bookmark this page to save your inputs.

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Result

Enter your values and tap Calculate.

How to use this calculator

Pick metric or imperial units, enter your height and weight, and tap Calculate. The result shows your BMI score plus the WHO adult category (underweight, normal, overweight, or obesity). Use it as a starting point — speak with a healthcare provider for a full health assessment.

BMI does not differentiate muscle from fat, so very muscular people may score higher than expected. For more precise body composition, look into DEXA scans, skinfold calipers, or bioelectrical impedance.

How to use the BMI Calculator

Enter your height and weight in either metric or imperial units. The calculator divides your weight in kilograms by your height in metres squared and returns your Body Mass Index along with the standard WHO adult category.

Example workflow

Choose your preferred unit system, type in your height and weight, and tap Calculate. Bookmark the page after your first result — your inputs are saved into the URL itself, so the bookmark restores your numbers next time.

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Frequently asked questions

What is BMI?

Body Mass Index (BMI) is a screening number derived from a person's height and weight. It is calculated as weight in kilograms divided by height in metres squared. BMI is widely used as a first-pass health indicator but does not measure body fat directly.

Which BMI categories does this calculator use?

Standard adult thresholds from the World Health Organization: under 18.5 is underweight, 18.5 to 24.9 is normal weight, 25.0 to 29.9 is overweight, and 30.0 or above is obesity. Children, athletes, and older adults often need different reference ranges.

Is BMI accurate for athletes or muscular people?

Not always. BMI does not distinguish muscle from fat, so a heavily-muscled person may register as overweight or obese while having low body fat. Body composition tools like DEXA scans, calipers, or bioimpedance give more accurate body-fat estimates.

Should children use the same BMI scale?

No. Children and teenagers are evaluated using BMI-for-age percentile charts that account for natural growth patterns, not the fixed adult thresholds. Pediatric BMI assessment should come from a healthcare provider.

Does my saved progress get sent to a server?

No. Your inputs live only in the URL of this page. When you bookmark the page, you save your data locally to your own device. Nothing is uploaded, stored on a server, or tracked.

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People also ask

Is BMI an accurate measure of health?

BMI is a population-level screening tool, not a diagnostic one. It does not distinguish between muscle and fat mass, and tends to overestimate health risk in muscular individuals and underestimate it in those with low muscle mass. The CDC and WHO recommend using BMI alongside waist circumference, blood pressure, blood glucose, and other clinical markers for a fuller picture.

What BMI is considered healthy for older adults?

Research suggests that slightly higher BMI values (25–27) may be associated with better outcomes in adults over 65, whereas underweight (BMI below 22) carries significant health risk in this age group. The standard 18.5–24.9 range was established for younger adults — discuss your specific target with your physician if you are over 65.

How does BMI differ for children vs adults?

For children and teenagers (ages 2–19), BMI is interpreted using age- and sex-specific percentile charts rather than fixed ranges. A child's BMI-for-age at the 95th percentile or higher is classified as obese; at the 85th–94th percentile, overweight. Adult cutoffs (18.5, 25, 30) do not apply to pediatric patients.

Real-world scenarios

Using BMI alongside waist circumference

If your BMI is 27 (overweight range) but your waist circumference is under 35 inches (women) or 40 inches (men), your metabolic risk may be lower than BMI alone suggests. Conversely, a BMI of 24 with a waist circumference above those thresholds may indicate higher risk than the BMI number implies. Use both metrics together for a more complete assessment.

Tracking BMI change during a weight loss program

A 5'8" person weighing 210 lbs has a BMI of 31.9. Losing 20 lbs drops BMI to 28.9 — still in the overweight range but no longer obese. Use the calculator to set intermediate weight targets that correspond to meaningful BMI milestones rather than tracking pounds alone, which gives a standardized health reference point alongside the number on the scale.

Athletes and the muscle mass limitation

An NFL linebacker at 6'2" and 245 lbs has a BMI of 31.5 — classified as obese. A competitive marathon runner at 5'10" and 145 lbs has a BMI of 20.8 — normal. BMI cannot distinguish between these situations. If you strength train regularly or have a high lean mass percentage, treat your BMI as one data point and supplement it with body fat percentage measured by DEXA, skinfold calipers, or a BodPod.