Body Mass Index Calculator – Calculate Your BMI Online

US Units



Result: kg/m²

Status: ?

Metric Units



Result: kg/m²

Status: ?

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Quick answer

BMI (Body Mass Index) is your weight in kilograms divided by the square of your height in metres. Enter your height and weight and this calculator instantly shows your BMI in either metric or US units.

Key facts

  • Uses the standard BMI formula: weight (kg) / height (m) squared
  • Supports both metric (cm, kg) and imperial (inches, lb) input units, converting internally to metric before calculating
  • Displays a standard weight-category label (e.g. underweight, normal, overweight) based on the result
  • Runs entirely in your browser via JavaScript, no data sent to a server
  • Free with no usage limit, informational only

What is this tool?

The BMI calculator estimates your Body Mass Index from your height and weight. BMI is a widely used screening number that helps indicate whether an adult's weight falls in an underweight, healthy, overweight or obese range.

How to use it

Select metric or imperial units, enter your height and weight, and your BMI value and weight-category label are calculated and displayed instantly.
  1. Choose your preferred units (metric or imperial).
  2. Enter your height.
  3. Enter your weight.
  4. View your calculated BMI value and its weight-category label instantly.

Example

Example: a height of 170 cm and weight of 65 kg gives a BMI of approximately 22.49, which falls in the "Normal" weight-category range.

How it works

Two standard formulas are supported:

  • Metric: BMI = weight (kg) ÷ height² (m²)
  • US units: BMI = 703 × weight (lb) ÷ height² (in²)

Common adult ranges: below 18.5 underweight, 18.5–24.9 healthy, 25–29.9 overweight, 30 and above obese.

Common use cases

  • A quick health check between doctor visits
  • Tracking progress during a fitness or weight-management plan
  • Converting between metric and US BMI conventions

Benefits

Free, instant, supports both unit systems, and uses the same standard formula used in general health screening.

Limitations

BMI does not distinguish muscle from fat and does not account for age, sex, ethnicity or body composition. Athletes can show a high BMI without excess fat. BMI is a screening value, not a diagnosis — talk to a healthcare professional before making health decisions.

Privacy & your data

All calculations run entirely in your browser using JavaScript. Your height and weight are never sent to our servers.

Frequently asked questions

What is a healthy BMI?

For most adults a BMI between 18.5 and 24.9 is considered the healthy range. Below 18.5 is underweight, 25–29.9 is overweight and 30+ is classed as obese.

Does BMI account for muscle mass?
No. BMI is based only on height and weight, so muscular individuals may show a higher BMI despite having low body fat -- it is a general screening tool, not a precise body-composition measurement.
Is BMI accurate for athletes?

Not always. BMI cannot tell muscle from fat, so muscular people may read as "overweight" despite low body fat. Use it as a rough screen, not a verdict.

Is a high or low BMI a medical diagnosis?
No. This tool provides an informational BMI estimate and standard category label only; it is not a medical diagnosis. Consult a healthcare professional for a full assessment of your health.
Is my data stored when I use this calculator?

No. The calculation happens in your browser — the values you type never leave your device.

Can I use imperial units instead of metric?
Yes. You can enter height in inches and weight in pounds; the tool converts these to metric internally before calculating your BMI.
Is my height and weight data stored anywhere?
No. All calculations happen locally in your browser; nothing is sent to or stored on the A2Z Tools server.

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