How to use this calculator
Start by choosing your preferred unit system — Imperial (feet, inches, pounds) or Metric (centimeters, kilograms). Enter your height and weight, and the calculator will instantly display your BMI value, category, and where you fall on the BMI scale.
The results also show the healthy weight range for your specific height, so you can see the weight range that corresponds to a normal BMI of 18.5–24.9.
Understanding BMI categories
| Category | BMI Range | What it means |
|---|---|---|
| Underweight | Below 18.5 | May indicate nutritional deficiency or underlying health issues. Consult a doctor. |
| Normal | 18.5 – 24.9 | Generally associated with the lowest health risks related to weight. |
| Overweight | 25.0 – 29.9 | Elevated risk for cardiovascular disease, high blood pressure, and type 2 diabetes. |
| Obese | 30.0 and above | Significantly increased risk for multiple chronic conditions. Medical guidance recommended. |
Limitations of BMI
BMI is a population-level screening tool, not a clinical diagnosis. It uses only height and weight, so it cannot tell the difference between muscle, fat, bone, and water weight. A bodybuilder and a sedentary person of the same height and weight will have identical BMI scores — but very different health profiles.
BMI also doesn't account for where fat is stored. Visceral fat (around the organs) carries much higher health risks than subcutaneous fat (under the skin). Waist-to-hip ratio and waist circumference are often better indicators of metabolic risk.
Age, sex, and ethnicity all influence how BMI should be interpreted. Older adults tend to have more body fat at the same BMI as younger adults. The standard thresholds were developed using primarily White European populations and may not apply equally across all ethnic groups.
Frequently asked questions
What is BMI and how is it calculated?
BMI (Body Mass Index) is calculated by dividing your weight in kilograms by the square of your height in meters: BMI = kg / m². It's a quick, free screening tool used worldwide to categorize weight status.
What are the BMI categories?
The World Health Organization defines four categories: Underweight (below 18.5), Normal (18.5–24.9), Overweight (25–29.9), and Obese (30 and above). Some systems further divide obesity into Class I, II, and III.
Is BMI accurate for athletes and muscular people?
Not always. Muscle is denser than fat, so athletes and people who lift weights regularly may have a BMI in the "overweight" range while having a low body fat percentage. In these cases, body fat percentage or a DEXA scan gives a more accurate picture.
Should I use BMI as my only health indicator?
No. BMI is a useful starting point, but it doesn't tell the whole story. Blood pressure, cholesterol, blood sugar, fitness level, diet quality, and waist circumference all matter for long-term health. Talk to your doctor for a comprehensive assessment.