BMI Calculator – Check Your Body Mass Index
Check your Body Mass Index from your height and weight. See your BMI category, healthy weight range, and what your result means for your health.
Coach Note: BMI is a useful screening tool, but it doesn't measure muscle mass directly. For athletic clients, combine BMI with waist measurements or body fat estimates.
Enter Your Measurements
Calculate your Body Mass Index
Adding waist measurement shows your waist-to-height ratio (bonus insight)
Your BMI Results
Body Mass Index Analysis
Enter your measurements
Your BMI results will appear here
BMI Categories (WHO Standards)
< 18.5
May indicate nutritional deficiency
18.5 - 24.9
Optimal range for most adults
25 - 29.9
Increased health risk
≥ 30
Significantly elevated health risk
What is BMI (Body Mass Index)?
Simple Weight-to-Height Ratio
BMI is a simple ratio of weight to height used to estimate whether weight is in a healthy range. It's calculated by dividing your weight (kg) by your height squared (m²).
Quick Health Screening
Used worldwide by healthcare professionals as a first-pass screening tool for potential weight-related health risks. It's quick, non-invasive, and requires no special equipment.
What is a BMI Calculator and What Does Your Result Mean?
A BMI calculator computes your Body Mass Index — a numerical value derived from your height and weight that categorises your body size relative to standard health thresholds. BMI is one of the most widely used screening tools in healthcare and fitness, providing a quick, equipment-free estimate of whether a person's weight may be affecting their health.
BMI is useful for the general population, healthcare professionals, coaches working with diverse client groups, and anyone who wants a simple starting benchmark for understanding their body weight in relation to their height. Governments and health organisations use BMI at a population level to track obesity trends, while fitness professionals use it as one of several client assessment data points.
The BMI formula divides your weight in kilograms by your height in metres squared (kg/m²). A healthy BMI range of 18.5–24.9 is associated with the lowest risk of weight-related health conditions including cardiovascular disease and type 2 diabetes. Values below 18.5 indicate underweight status, 25–29.9 is overweight, and 30 or above is classified as obese.
It is important to understand what BMI does not measure. It cannot distinguish between fat mass and lean muscle mass, which is why muscular individuals often show artificially high BMI values. For a more complete picture of your body composition, combine your BMI result with waist circumference — which this calculator also provides if you enter your waist measurement — or use our Body Fat Calculator for a more detailed analysis.
How to Use This BMI Calculator
- Select your unit system: metric (kg and cm) or imperial (lbs, feet, and inches).
- Enter your weight and height accurately — use a scale and measuring tape rather than estimating.
- Optionally, enter your waist circumference to see your waist-to-height ratio as an additional health indicator.
- Click "Calculate My BMI" to see your BMI score, category, and healthy weight range for your height.
- Use the result alongside other metrics — especially if you are muscular or very active — for a more accurate health assessment.
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When BMI Can Be Misleading
Very Muscular People
Athletes and bodybuilders may have high BMI due to muscle mass, not excess fat. Muscle weighs more than fat per unit volume.
Pregnancy
BMI calculations don't account for pregnancy weight gain, which is normal and healthy. Use pre-pregnancy BMI for reference.
Older Adults
Older adults with low lean mass may have "normal" BMI but unhealthy body composition. Muscle loss with age affects accuracy.