BMI Calculator
Calculate your Body Mass Index (BMI) to check if your weight is in a healthy range. Supports both metric and imperial units.
BMI Categories
| Category | BMI Range |
|---|---|
| Underweight | Less than 18.5 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese | 30.0 and above |
How to Use the BMI Calculator
This calculator makes it easy to determine your Body Mass Index in just a few steps:
- Choose your unit system — Select the Metric tab (kg/cm) or Imperial tab (lbs/ft) depending on your preference.
- Enter your weight and height — Type your weight and height into the respective fields. For imperial, enter feet and inches separately.
- Click "Calculate BMI" — Your BMI value, category, and healthy weight range will be displayed instantly.
- Review the BMI categories table — Compare your result against the standard WHO BMI classification ranges.
About BMI (Body Mass Index)
Body Mass Index (BMI) is a widely used screening tool that estimates body fat based on a person's weight relative to their height. Developed by Belgian mathematician Adolphe Quetelet in the 1830s, BMI is calculated using the formula: BMI = weight (kg) / height (m)².
BMI is commonly used by healthcare providers to identify potential weight-related health risks. While it does not directly measure body fat percentage, it provides a quick and easy way to categorize individuals into weight status groups. The World Health Organization (WHO) recognizes four primary BMI categories: underweight, normal weight, overweight, and obese.
It is important to note that BMI has limitations. It does not distinguish between muscle mass and fat mass, meaning that muscular individuals may have a high BMI without excess body fat. Age, gender, ethnicity, and body composition can all influence how BMI should be interpreted. For a complete health assessment, consult with a medical professional.
BMI Worked Examples
Below are step-by-step BMI calculations for different heights and weights to help you understand how the formula works:
- 5'10" and 180 lbs (imperial): Convert height to inches: 5 × 12 + 10 = 70 inches. Apply the formula: (180 × 703) ÷ (70 × 70) = 126,540 ÷ 4,900 = 25.8 (Overweight).
- 170 cm and 65 kg (metric): Convert height to meters: 170 ÷ 100 = 1.70 m. Apply the formula: 65 ÷ (1.70 × 1.70) = 65 ÷ 2.89 = 22.5 (Normal weight).
- 5'4" and 130 lbs (imperial): Height in inches: 5 × 12 + 4 = 64 inches. Formula: (130 × 703) ÷ (64 × 64) = 91,390 ÷ 4,096 = 22.3 (Normal weight).
- 180 cm and 95 kg (metric): Height in meters: 1.80 m. Formula: 95 ÷ (1.80 × 1.80) = 95 ÷ 3.24 = 29.3 (Overweight).
- 5'6" and 210 lbs (imperial): Height in inches: 5 × 12 + 6 = 66 inches. Formula: (210 × 703) ÷ (66 × 66) = 147,630 ÷ 4,356 = 33.9 (Obese).
- 160 cm and 50 kg (metric): Height in meters: 1.60 m. Formula: 50 ÷ (1.60 × 1.60) = 50 ÷ 2.56 = 19.5 (Normal weight).
Quick Reference: Healthy Weight Ranges by Height
The following table shows the healthy weight range (BMI 18.5 to 24.9) for common heights. Use this to quickly see where you fall.
| Height | Healthy Weight (lbs) | Healthy Weight (kg) |
|---|---|---|
| 5'0" (152 cm) | 95 – 128 lbs | 43 – 58 kg |
| 5'3" (160 cm) | 105 – 141 lbs | 47 – 64 kg |
| 5'6" (168 cm) | 115 – 155 lbs | 52 – 70 kg |
| 5'9" (175 cm) | 126 – 169 lbs | 57 – 77 kg |
| 6'0" (183 cm) | 137 – 184 lbs | 62 – 83 kg |
| 6'3" (191 cm) | 148 – 200 lbs | 67 – 91 kg |
Frequently Asked Questions
BMI (Body Mass Index) is a numerical value calculated from your weight and height. The formula is BMI = weight (kg) / height (m)². For imperial units, the formula is BMI = (weight in lbs × 703) / (height in inches)². It is used as a screening tool to identify potential weight problems in adults.
The standard BMI categories for adults are: Underweight (BMI below 18.5), Normal weight (BMI 18.5 to 24.9), Overweight (BMI 25 to 29.9), and Obese (BMI 30 and above). These categories apply to both men and women aged 20 and older.
BMI is a useful general indicator but has limitations. It may overestimate body fat in athletes and muscular individuals, and underestimate it in older adults who have lost muscle mass. It also does not account for differences in body composition related to age, gender, or ethnicity. Always consult a healthcare professional for personalized advice.
A healthy BMI is generally considered to be between 18.5 and 24.9. Within this range, you are less likely to develop weight-related health issues such as heart disease, type 2 diabetes, and certain cancers. However, BMI is just one factor in overall health assessment.
For children and teens aged 2 to 19, BMI is calculated the same way but interpreted differently using age- and sex-specific percentile charts from the CDC. A child's BMI percentile shows how their BMI compares to other children of the same age and sex. The standard adult BMI categories do not apply to minors.
A BMI of 25 or above is associated with increased risk of type 2 diabetes, heart disease, high blood pressure, sleep apnea, certain cancers, and joint problems. The risk generally increases as BMI rises. However, BMI is just one risk factor, and overall health depends on many additional factors including diet, physical activity, and family history.
BMI does not distinguish between muscle mass and fat mass. Since muscle is denser than fat, highly muscular individuals like bodybuilders, football players, or sprinters may have a BMI in the overweight or obese range despite having very low body fat. In these cases, other measurements like body fat percentage, waist circumference, or skinfold tests provide a more accurate picture.
For most adults, checking BMI once or twice a year is sufficient to monitor weight trends. If you are actively trying to lose or gain weight, monthly checks can help track progress. Keep in mind that day-to-day weight fluctuations from water retention and food intake are normal, so focus on long-term trends rather than single measurements.