BMI Calculator

What this calculator does

This BMI calculator takes your height and weight — in either metric or US units — and computes your Body Mass Index using the standard WHO formula. It then classifies your BMI into one of four weight categories, shows where you fall on a visual scale, and calculates the weight range that would put your BMI in the Normal weight band for your specific height.

Formula

BMI is calculated by dividing weight in kilograms by the square of height in meters:

For US units, height in feet and inches is converted to centimetres and weight in pounds to kilograms before applying the formula. The result is rounded to one decimal place for display, but the full-precision value is used for category classification.

How to use it

1. Select your preferred unit system: US (ft, lbs) or Metric (cm, kg).
2. Enter your height — feet and inches for US, centimetres for metric.
3. Enter your weight in pounds or kilograms.
4. Click Calculate to see your BMI, WHO category, scale position, and healthy weight range.

Example

A person who is 5'9" (175.3 cm) and weighs 160 lbs (72.6 kg):

• Height in metres: 1.753 m
• BMI = 72.6 / (1.753 × 1.753) ≈ 23.6
• Category: Normal weight (BMI 18.5–24.9)
• Healthy weight range for this height: approximately 113–153 lbs

What the result means

Your BMI number is a ratio of weight to height. The WHO uses four thresholds to categorize adults: below 18.5 is Underweight, 18.5 to 24.9 is Normal weight, 25.0 to 29.9 is Overweight, and 30.0 and above is Obese. The healthy weight range shows the weight that would produce a BMI between 18.5 and 24.9 specifically for your height. A higher BMI is associated with increased risk of certain health conditions, but BMI alone does not diagnose any condition.

Assumptions and limitations

• BMI does not distinguish between fat mass and lean mass. Athletes and people with high muscle mass may have a high BMI without excess body fat.
• The same BMI thresholds are applied to all adult ages, but body composition changes with age. Older adults may have more body fat at a given BMI than younger adults.
• Research suggests different BMI thresholds may be more appropriate for some ethnic groups, including South Asian and East Asian populations.
• BMI thresholds are not applied to children and adolescents. Age- and sex-specific growth charts should be used instead.
• This calculator does not account for pregnancy, medical conditions, or medications that affect weight or body composition.
• BMI is a screening tool only, not a clinical diagnosis. A healthcare professional should be consulted for health assessments.