BMI Calculator: What Is a Healthy BMI and How to Calculate Yours
Body Mass Index is one of the most widely used health screening tools in the world. Doctors, fitness professionals, and health organisations use it as a quick way to assess whether someone falls into a healthy weight range.
But BMI is also one of the most misunderstood measurements. It tells you something useful, but not the complete picture. Here is what you need to know.
What Is BMI?
BMI stands for Body Mass Index. It is a simple calculation that uses your height and weight to estimate whether you are underweight, a healthy weight, overweight, or obese.
The formula is straightforward:
BMI = weight (kg) / height (m)²
For example, if you weigh 75kg and are 1.75m tall: 75 / (1.75 × 1.75) = 24.5
That places you in the "healthy weight" category.
BMI Categories
The World Health Organisation defines these standard categories:
Below 18.5 Underweight 18.5 – 24.9 Healthy weight 25.0 – 29.9 Overweight 30.0 – 34.9 Obese (Class I) 35.0 – 39.9 Obese (Class II) 40.0 and above Obese (Class III)These ranges apply to adults aged 20 and over. Children and teenagers use age-specific percentile charts.
How to Calculate Your BMI
Step 1: Enter Your Details
Input your height and weight. You can use metric (kg/cm) or imperial (lbs/ft), the calculator handles both.
Step 2: View Your Result
Your BMI is calculated instantly, along with your category and where you sit on the healthy range scale.
Step 3: Understand the Context
Use the result as a starting point, not a diagnosis. Consider your age, muscle mass, and overall fitness level alongside the number.
Try it now: Use our free BMI Calculator to check your BMI instantly in your browser.
What BMI Does Not Tell You
BMI is useful but limited. It does not account for:
- Muscle mass, athletes and gym-goers often have a "high" BMI because muscle weighs more than fat
- Body fat distribution, where you carry weight matters. Belly fat poses more health risks than fat on your hips
- Age and gender differences, older adults may have more body fat at the same BMI as younger adults
- Ethnic variations, health risks associated with BMI differ across ethnic groups
For a more complete picture, consider checking your body fat percentage with our Body Fat Calculator, or calculate your daily calorie needs with the Calorie Calculator.
When to Use BMI
BMI works best as a general screening tool. It is helpful for:
- Tracking changes over time, monitoring whether you are moving in the right direction
- Population-level health assessments, comparing health trends across groups
- Initial health check conversations, giving you and your doctor a starting point
- Setting realistic goals, understanding what a healthy weight range looks like for your height
It is not a substitute for a proper health assessment. If your BMI suggests you may be overweight or underweight, speak with a healthcare professional who can look at the full picture.
Try It Yourself
Curious about your BMI? Our free BMI Calculator gives you an instant result with a clear category breakdown and browser-based calculations.