How to Calculate Your BMI
BMI is calculated by dividing your weight in kilograms by the square of your height in meters.
Metric formula:
BMI = weight (kg) / height (m)²
Imperial formula:
BMI = 703 × weight (lbs) / height (in)²
For example, a person who is 5'9" and weighs 180 lbs has a BMI of approximately 26.6, which falls in the overweight category.
Our calculator handles both metric and imperial inputs automatically and displays your result alongside the standard BMI weight status categories.
BMI Chart for Men and Women
The standard BMI categories defined by the CDC and WHO apply to both men and women aged 20 and older.
| BMI Range | Weight Status |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obese |
Note that BMI is a screening tool, not a diagnostic measure. Two people with the same BMI can have very different body compositions depending on muscle mass, bone density, and fat distribution.
Healthy BMI Range by Age
While the standard BMI chart applies broadly to adults, age can influence how BMI correlates with health risk.
| Age Group | Recommended BMI Range |
|---|---|
| 20 – 34 | 19 – 24 |
| 35 – 44 | 20 – 25 |
| 45 – 54 | 21 – 26 |
| 55 – 64 | 22 – 27 |
| 65 and older | 23 – 28 |
Older adults tend to carry more body fat at the same BMI as younger adults, which is why slightly higher BMI values are considered acceptable with age. Always consult a healthcare provider for a personalized assessment.
BMI Calculator — Metric and Imperial
Our calculator supports both measurement systems so you can enter your numbers in whatever format is most familiar.
- Metric inputs: weight in kilograms, height in centimeters or meters
- Imperial inputs: weight in pounds, height in feet and inches
The result is the same regardless of which system you use. Your BMI score is a unitless number that places you in one of the four standard weight status categories.
What Is a Good BMI Score?
A BMI between 18.5 and 24.9 is considered normal or healthy weight for most adults. However, BMI alone does not tell the full story of your health.
What BMI does well:
- Provides a quick, low-cost screening tool
- Correlates reasonably well with body fat in large populations
- Helps identify potential weight-related health risks
Where BMI falls short:
- Does not account for muscle mass — athletes often show high BMI despite low body fat
- Does not measure fat distribution — abdominal fat carries higher health risk than fat elsewhere
- May underestimate risk in older adults who have lost muscle
- Research suggests BMI cutoffs may not apply equally across all ethnic groups
For a more complete picture, combine your BMI result with waist circumference, body fat percentage, and a consultation with your physician.
Frequently Asked Questions
What is a healthy BMI for a woman?
For adult women, a BMI between 18.5 and 24.9 is considered healthy. However, women tend to carry more body fat than men at the same BMI, so waist circumference and body fat percentage provide additional context. Women with a waist measurement above 35 inches may face elevated health risks even within a normal BMI range.
What BMI is considered obese?
A BMI of 30.0 or higher is classified as obese according to CDC and WHO guidelines. Obesity is further divided into three classes: Class 1 (BMI 30–34.9), Class 2 (BMI 35–39.9), and Class 3 or severe obesity (40 and above).
How can I lower my BMI?
Lowering your BMI requires reducing body fat through a sustained caloric deficit combined with regular physical activity. A combination of strength training and cardiovascular exercise is most effective. Crash diets or extreme restriction are not recommended as they often lead to muscle loss and weight regain.
Is BMI accurate for athletes?
No, BMI is a poor measure for athletes and highly muscular individuals. Muscle is denser than fat, so athletes often register a high BMI despite having very low body fat. In these cases, body fat percentage measurement through DEXA scan, hydrostatic weighing, or skinfold calipers provides a far more accurate assessment.
What is a normal BMI range for adults?
The normal BMI range for adults is 18.5 to 24.9. This applies to both men and women aged 20 and older regardless of age, though some guidelines suggest slightly higher ranges are acceptable for adults over 65.
How much should I weigh for my height?
Healthy weight varies by height. For reference, a person who is 5'6" has a healthy weight range of approximately 115 to 154 pounds. A person who is 5'10" has a healthy weight range of approximately 132 to 174 pounds. Use our BMI calculator to find the healthy weight range specific to your height.
Does BMI account for muscle mass?
No. BMI only uses total body weight and height. It cannot distinguish between fat mass and lean muscle mass. This is one of the primary limitations of BMI as a health screening tool, particularly for strength athletes, bodybuilders, and physically active individuals.
What is the BMI formula in kg and cm?
Divide your weight in kilograms by your height in meters squared. For example, if you weigh 70 kg and are 175 cm tall: BMI = 70 / (1.75 × 1.75) = 22.9, which falls in the normal weight range.