Calculator
What the BMI Calculator does
BMI Calculator: calculates Your BMI, Category and Healthy Weight for Your Height from Units, Your Weight and Your Height. Formula: BMI = weight (kg) / height (m)^2. Example: units Metric (kg, cm), your weight 70 kg and your height 170 cm gives your BMI 24.22.
Give the BMI Calculator your Units, Your Weight, Your Height and Your Weight and it works out Your BMI, Category and Healthy Weight for Your Height. Adjust anything and the figures re-derive on the spot.
Most people who open the BMI Calculator are readers checking a number from a clinic. Knowing how a figure is derived makes it much easier to interpret sensibly.
Your data stays on your machine. Once the page has loaded you could disconnect entirely and it would still work.
The field table, the method and a worked example are documented after the tool for anyone who wants to check the working.
What do the BMI Calculator fields mean?
The BMI Calculator uses 6 inputs. A filled form means you can test one idea immediately instead of sourcing every input first.
| Field | What to enter | Default |
|---|---|---|
| Units | choose from Metric (kg, cm) or Imperial (lb, ft/in) | Metric (kg, cm) |
| Your Weight | measured in kg; accepts 20 to 200 | 70 |
| Your Height | measured in cm; accepts 80 to 230 | 170 |
| Your Weight | measured in lb; accepts 40 to 450 | 154 |
| Height (feet) | measured in ft; accepts 2 to 8 | 5 |
| Height (inches) | measured in in; accepts 0 to 11.9 | 7 |
How does the BMI Calculator work?
The result is a ratio, not a body-fat measurement. It does not distinguish muscle from fat.
Each field is verified before use; failures are reported explicitly rather than swallowed.
Worked example
These are the values the BMI Calculator loads by default, and the result it produces from them. Below is the same computation the tool performs on load, step by step.
| Units | Metric (kg, cm) |
|---|---|
| Your Weight | 70 kg |
| Your Height | 170 cm |
| Your Weight | 154 lb |
| Height (feet) | 5 ft |
| Height (inches) | 7 in |
| Your BMI | 24.22 |
|---|---|
| Category | Normal |
| Healthy Weight for Your Height | 53.5 to 72.0 kg |
| Distance from Healthy Range | You are inside the healthy weight range for your height. |
| What this means | Your BMI is in the typical healthy range for most adults. Keep balanced eating and regular activity. |
The WHO categories this calculator reads your result against
The World Health Organization defines adult weight categories by BMI alone: below 18.5 is underweight, 18.5 to 24.9 is the healthy range, 25 to 29.9 is overweight and 30 or above is obesity, split again at 35 and 40. The same cut-offs apply to men and women and do not change with age between 20 and 65. A 70 kg person who is 1.70 m tall has a BMI of 24.2, near the top of the healthy band.
| Category | BMI range | What it indicates |
|---|---|---|
| Underweight | below 18.5 | Below the range with the lowest observed health risk |
| Healthy weight | 18.5 to 24.9 | Reference range for adults aged 20 to 65 |
| Overweight | 25.0 to 29.9 | Raised risk of type 2 diabetes and cardiovascular disease, increasing with BMI |
| Obesity class I | 30.0 to 34.9 | Clinical obesity; risk rises steeply from here |
| Obesity class II | 35.0 to 39.9 | Severe obesity |
| Obesity class III | 40 and above | Very severe obesity |
What to keep in mind
- WHO also recommends lower action points for people of Asian descent, 23 and 27.5 instead of 25 and 30, because metabolic risk rises at a lower BMI in those populations. Several Indian clinical guidelines go further and use 23 and 25.
- BMI cannot tell muscle from fat. A muscular 90 kg person at 1.80 m has a BMI of 27.8 and is "overweight" on this table without carrying excess fat.
- Waist circumference or waist-to-height ratio catches abdominal fat that BMI misses; a waist more than half your height is the simplest extra check.
- For anyone under 20 the adult table does not apply at all. The child and teen calculators read BMI as an age-and-sex percentile instead.
World Health Organization, Obesity: preventing and managing the global epidemic (WHO Technical Report Series 894, 2000); WHO Expert Consultation, Appropriate body-mass index for Asian populations, The Lancet 2004;363:157-63.
Sources: WHO: body mass index and a healthy lifestyle · WHO Expert Consultation 2004, The Lancet (PubMed)
Read next: Understanding BMI: What the Number Measures, and What It Misses
How to use it
- Pick a value for Units: the options are Metric (kg, cm) or Imperial (lb, ft/in).
- Put Your Weight in kg (20 to 200).
- Key in Your Height in cm (80 to 230).
- Fill in Your Weight in lb (40 to 450).
- Type Height (feet) in ft (2 to 8).
- Enter Height (inches) in in (0 to 11.9).
- Skip the submit button; there is not one. Editing is enough.
- Check Your BMI, Category, Healthy Weight for Your Height, Distance from Healthy Range and What this means on the right.
- Copy Link when you want to return to this exact configuration; Print when someone needs it on paper.
What this tool does not do
- These formulas come from population averages and cannot account for your medical history.
- This is a screening estimate, not a diagnosis.
- Precision beyond what the inputs justify is not meaningful, however many digits appear.
- The tool trusts your numbers completely, so a mis-keyed digit propagates straight through.
Frequently asked questions
Enter Your Weight in kg, Your Height in cm, Your Weight in lb, Height (feet) in ft and Height (inches) in in. Every input names its unit, and every output does too, which removes the usual source of error.
Your Weight accepts 20 to 200 kg. Go outside it and you get an error against that specific field instead of a misleading number.
With the values loaded when the page opens, your BMI comes out as 24.22. Adjust any field to see how much the answer depends on it.
No. There is no account, no session and no storage. The values exist only while the tab is open.
No charge. Everything on the page is available without signing in.
The computation is exact. What it is computing is a population average, which is a different thing from a fact about you, so read the number as a prompt to ask a better question.