BMI Calculator

Using the bmi estimate

Body mass index relates weight to height using a simple ratio. It is a screening measure, not a diagnosis or a direct measurement of body fat. This calculator helps you check the arithmetic and see the adult reference category, but it cannot determine whether an individual is healthy or what treatment they need.

Step-by-step inputs

1. Units. Replace the starting value with your own, keeping the displayed unit and period. Starting example: US .
2. Height · feet. Replace the starting value with your own, keeping the displayed unit and period. Starting example: 5 ft.
3. Height · inches. Replace the starting value with your own, keeping the displayed unit and period. Starting example: 10 in.
4. Weight. Replace the starting value with your own, keeping the displayed unit and period. Starting example: 170 lb.

Worked example with the starting values

Using the starting inputs, the estimate is Your BMI: 24.4 .

Healthy weight · adult screening

Adult healthy-weight range · lower

128.9 lb

Adult healthy-weight range · upper

173.5 lb

BMI Prime

0.98

Ponderal index

13.72 kg/m³

Make a useful comparison

Choose the correct measurement units and use current, reasonably accurate measurements. Enter height and weight in the units shown, not a mixture of metric and imperial units. Small height errors matter because height is squared in the formula.

For metric measurements, BMI is weight in kilograms divided by height in meters squared. For example, 70 kilograms and 1.75 meters gives 70 ÷ 1.75², or about 22.9. The unit conversion changes the arithmetic, not the underlying relationship.

Interpret an adult reference category alongside other information rather than as a verdict. Medical history, muscle mass, waist measurements and other clinical observations may provide context that this ratio cannot show.

Common mistakes to avoid

• BMI does not separate muscle from fat. Two people with the same height and weight can have different body composition and different health needs.
• Adult category thresholds should not be applied as a child or teen growth assessment. Age- and sex-specific growth references require a different interpretation.
• Pregnancy and some medical circumstances can make a standard weight-to-height interpretation inappropriate. Do not use the number alone to choose a diet, medication dose or exercise restriction.