BMI Calculator
Calculate your Body Mass Index and see which range you fall in.
Your BMI
22.5
Normal weight
Under
Normal
Over
Obese
About the BMI Calculator
Enter your height and weight and get your Body Mass Index in a second, along with the standard weight category it lands in. Gym-goers tracking a bulk or cut, patients interpreting a doctor's chart, and anyone starting a fitness journey all use BMI as the quickest screening number in health. This free BMI calculator works in centimetres and kilograms, runs entirely inside your browser — your measurements go nowhere — and needs no email, app install or sign-up. Read the number, note the band, and treat it as a starting point for a conversation, not a verdict.
One division, one category
BMI divides your weight in kilograms by the square of your height in metres: BMI = kg ÷ m². A height entered in centimetres is converted by dividing by 100 first, so 175 cm becomes 1.75 m and contributes 3.0625 m². The standard WHO bands then sort the result: below 18.5 is Underweight, 18.5–24.9 is Normal, 25–29.9 is Overweight, and 30 or above is Obese — the exact cutoffs this tool applies. Worth knowing honestly: several Asian-country guidelines, following the WHO-WPRO framework, flag elevated risk earlier, treating roughly 23 as the overweight threshold and 27.5 as obese, because body-fat and metabolic risk patterns differ at lower BMIs. This tool sticks to the standard global WHO cutoffs, so interpret results with your own regional and clinical context in mind.
What BMI quietly misses
BMI measures only how mass relates to height — it cannot tell muscle from fat, bone from belly. Muscular athletes routinely score "Overweight" while carrying very low body fat; conversely, someone sedentary with low muscle mass can score Normal despite unhealthy fat levels. There is no adjustment for age or sex, though body composition shifts meaningfully across both; older adults often carry more fat at the same BMI than younger ones. Fat distribution matters too — abdominal fat carries more metabolic risk than fat on hips and thighs, which is why waist measurement is a useful companion number. Children and teenagers need age-and-sex percentile charts rather than adult bands, and pregnancy invalidates BMI entirely. Treat the output as a population-level screening signal: cheap, fast and useful for spotting trends — not a diagnosis of anybody's health.
Using it sensibly over time
A single reading tells you little; the trend tells you plenty. Weigh in under comparable conditions — similar time of day, similar clothing, same scale — and watch the category boundary rather than obsessing over decimals. Your healthy-weight range is easy to derive from the tool's logic: multiply 18.5 and 24.9 by your height squared. For someone 1.75 m tall that spans about 56.7 kg to 76.3 kg — a wide, forgiving corridor worth knowing instead of chasing a single target number. If you train seriously, pair BMI with a waist measurement or a proper body-composition assessment so the gym does not lie to you. And if your reading lands outside the normal band persistently, take the trend to a doctor rather than to a stricter diet. This calculator is educational, not medical advice.
Real numbers, start to finish
A person weighing 70 kg at 1.75 m (entered as 175 cm) wants their BMI and category:
| Step | Value |
|---|---|
| Height squared | 1.75 × 1.75 = 3.0625 m² |
| BMI | 70 ÷ 3.0625 ≈ 22.9 |
| Category | Normal (18.5–24.9) |
| Healthy-weight span at 1.75 m | ≈ 56.7 – 76.3 kg |
70 kg · 1.75 m
At 22.9, this person sits comfortably mid-band — about as central as the normal range allows, with headroom in both directions. The healthy-weight corridor is the more actionable takeaway: anywhere between roughly 57 and 76 kg keeps them normal, so small fluctuations cause no alarm. Had the height been entered as 175 instead of 1.75, the result would be nonsense — the tool expects centimetres and converts internally.
Video slot: bmi-calculator-walkthrough.mp4
Entering 175 cm and 70 kg to show the 22.9 Normal result, then sliding weight upward past 76 kg to demonstrate the category flipping to Overweight at the 25 boundary.
Coming soonHow to Use BMI Calculator Online
Follow these simple steps to use BMI Calculator securely in your web browser.
- 1
Select Units
Choose Metric (kg & cm) or Imperial (lbs & feet/inches) units.
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- 2
Enter Height & Weight
Type your height and body weight into the inputs.
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- 3
Click to Calculate Category
Click calculate to view your BMI score, WHO weight category, and healthy weight range.
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Features & Specifications
Metric Formula
BMI = weight (kg) / [height (m)]^2
Imperial Formula
BMI = [weight (lbs) / height (in)^2] * 703
Standard
World Health Organization (WHO) BMI Classifications
Privacy Status
100% In-Browser Local Processing
100% Free & Private In-Browser Processing
Rupix operates on a zero-upload architecture. All computations, file parsing, and transformations occur locally inside your web browser. No document bytes, sensitive text, or personal data are ever uploaded or transmitted to remote servers.
Why use Rupix BMI Calculator?
Metric & Imperial Support
Switch easily between kilograms/centimeters and pounds/feet/inches.
WHO Weight Classification
Classifies scores into Underweight, Normal, Overweight, and Obese categories.
Ideal Weight Range
Displays target healthy weight range corresponding to a normal BMI.