Turn height and weight into a clear health screening view

BMI is a simple ratio of weight to height. It is widely used as a first screen for weight categories. This page keeps the logic simple, then adds helpful outputs like a healthy weight range estimate, charts, comparison, and a printable PDF layout.

BMI and category Healthy weight range Charts and PDF export Compare and save
BMI
Single number summary
Range
Estimated healthy kg range
Tools
Charts, compare, PDF

How to use the BMI Calculator

  1. 1

    Enter height

    Type your height and choose a unit. You can use centimeters, inches, or feet.

  2. 2

    Enter weight

    Type your weight and choose kilograms or pounds.

  3. 3

    Optional details

    Age can adjust the category logic for older adults in this simplified model. Gender is optional and saved with scenarios.

  4. 4

    Calculate and compare

    Press Calculate to see BMI, category, charts, and a PDF export layout. Save scenarios to compare inputs over time.

Detailed guide and references▶

What BMI is

Body Mass Index (BMI) is a simple calculation using height and weight to screen for weight categories that may lead to health problems. It is not a diagnosis. It is a starting point that can be combined with other indicators.

Person holding a paper with BMI message
BMI is a simple screening number based on height and weight

Formula

The standard BMI formula is:

  • Metric units: BMI = weight (kg) / (height (m)) squared
  • Imperial units: BMI = 703 times weight (lb) / (height (in)) squared

This calculator converts your inputs to meters and kilograms, then applies the metric formula internally.

Categories

A commonly used adult BMI category set is:

  • Underweight: BMI less than 18.5
  • Normal weight: BMI 18.5 to 24.9
  • Overweight: BMI 25 to 29.9
  • Obesity Class I: BMI 30 to 34.9
  • Obesity Class II: BMI 35 to 39.9
  • Obesity Class III: BMI 40 or greater

For older adults, some interpretations use a slightly higher range. This page applies a simple adjustment when age is 65 or older.

Limitations

BMI is useful, but it has limitations.

It does not measure body fat directly

  • It cannot separate fat, muscle, and bone mass.
  • It may overestimate fat in very muscular people.
  • It may underestimate fat in older adults with lower muscle mass.

Consider other indicators

  • Waist circumference
  • Body fat percentage
  • Blood pressure and lipid profile
  • Diet, sleep, and physical activity

Practical tips

  1. Measure height and weight accurately and consistently.
  2. Use BMI as a screening metric, not as a full health assessment.
  3. Track trends over time and compare scenarios on this page.
  4. Consult a healthcare professional if you need clinical guidance.

FAQs

Is BMI a diagnosis?▶

No. BMI is a screening metric based on height and weight. It does not directly measure body fat or overall health.

Why can BMI be inaccurate for athletes?▶

BMI cannot distinguish fat from muscle. People with high muscle mass can have a high BMI without excess fat.

What is the healthy BMI range used here?▶

This tool uses BMI 18.5 to 24.9 to estimate a healthy weight range for adults.

Does age change BMI interpretation?▶

Sometimes. This calculator applies a simple adjustment when age is 65 or older, but it is still a simplified estimate.

Key takeaways

  • BMI is a fast screening metric, not a diagnosis
  • Healthy range is estimated from your height using common BMI thresholds
  • Charts help you visualize how current weight compares to the range
  • Save scenarios to compare measurements over time
  • Use professional guidance for clinical decisions

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Calculator

Enter height and weight, then press Calculate

These results are for general reference only and may differ from clinical assessments.