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BMI Calculator

Calculate your Body Mass Index (BMI) from your height and weight, see which weight category you fall into, and find the healthy weight range for your height.

Enter your weight in pounds.

Your BMI

Health note: BMI is a screening measure only — it is not medical advice and not a diagnosis. It does not account for muscle mass, bone density, body composition, age, sex or ethnicity, so athletes and very muscular people can score as "overweight" while being perfectly healthy, and a "normal" BMI does not guarantee good health. If you are concerned about your weight or health, talk to a qualified healthcare professional.

How It Works

Body Mass Index is a simple ratio of weight to height, designed to estimate whether a person's weight is in a typical range for their height. The metric formula is BMI = weight in kilograms ÷ height in meters squared. The US formula gives the same result using pounds and inches: BMI = 703 × weight in pounds ÷ height in inches squared. The 703 is just the conversion factor that makes the two formulas agree. This calculator converts your entries to metric first and then applies the standard formula.

Your BMI is then placed into one of four adult categories used by health organizations worldwide: underweight (below 18.5), normal weight (18.5–24.9), overweight (25–29.9), and obese (30 and above). The healthy weight range shown is the range of weights that would put your BMI between 18.5 and 24.9 at your height — found by working the formula backwards: weight = BMI × height², once with 18.5 and once with 24.9.

Worked example: a person who is 5 feet 10 inches tall (70 inches, or 1.78 m) and weighs 170 lb (77.1 kg) has a BMI of 703 × 170 ÷ 70² = 119,510 ÷ 4,900 = 24.4, which falls in the normal weight range (18.5–24.9). Their healthy weight range is 18.5 × 1.78² = 58.5 kg (129 lb) up to 24.9 × 1.78² = 78.7 kg (174 lb). So at 170 lb they are near the top of the healthy range for their height.

Frequently Asked Questions

What is a good BMI?

For most adults, a BMI between 18.5 and 24.9 is classified as normal weight. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obese. These cut-offs are a screening guide, not a verdict on your health.

Is BMI accurate?

BMI is a useful population-level screening tool, but it has real limits for individuals: it cannot tell muscle from fat, so athletes may score high despite low body fat, and it does not consider where fat is stored, age, sex or ethnicity. Doctors usually combine it with other measures such as waist circumference, blood pressure and blood tests.

How is the healthy weight range calculated?

It is the range of weights that gives a BMI between 18.5 and 24.9 at your height, using weight = BMI × height². For example, at 5'10" the healthy range is about 129–174 lb.

Does BMI work for children and teenagers?

Not with these adult cut-offs. For ages 2–19, BMI is compared against age- and sex-specific growth-chart percentiles instead. This calculator uses the adult categories only.

What should I do if my BMI is outside the normal range?

Treat it as a prompt to learn more, not a cause for alarm. A single number cannot capture your health — speak with a doctor or other qualified healthcare professional, who can look at the full picture before suggesting any changes.

Last updated: November 2026