BMI Calculator
Calculate your Body Mass Index from height and weight. See your BMI category, ideal weight range, and health risk assessment.
Our free BMI Calculator tells you where your body weight stands relative to your height using the Body Mass Index formula recommended by the World Health Organization. Enter your height and weight in metric or… Fill in the fields and see your result. Everything is computed on your device—we don't collect or store your inputs.
About This Calculator
Our free BMI Calculator tells you where your body weight stands relative to your height using the Body Mass Index formula recommended by the World Health Organization. Enter your height and weight in metric or imperial units and instantly see your BMI value, weight category (underweight, normal, overweight, or obese), and the healthy weight range for your height. BMI is the most widely used screening tool by doctors, fitness coaches, and health-insurance providers to flag potential weight-related risks such as heart disease, type-2 diabetes, and joint problems. Use it as a quick health check, a starting point for a fitness plan, or a benchmark to track progress over time.
How It Works
BMI is calculated with the formula: BMI = weight (kg) / height (m) squared. For imperial units the equivalent is BMI = (weight in pounds x 703) / (height in inches) squared. The result is compared against WHO categories: below 18.5 is underweight, 18.5-24.9 is normal, 25-29.9 is overweight, and 30 or above is obese. The calculator also computes the healthy weight range for your height (the weight that would give a BMI between 18.5 and 24.9) so you can set a realistic target.
Example Calculation
Example: A person who weighs 70 kg and is 1.75 m tall has a BMI of 70 / (1.75 x 1.75) = 22.9, which falls in the normal range (18.5-24.9). For the same height, the healthy weight range is approximately 56.7 kg to 76.3 kg.
How to Use
- Enter your values in the calculator fields above
- Click the calculate button or let the calculator auto-update
- Review your results instantly
- Adjust values as needed to see different scenarios
Frequently Asked Questions
What is a healthy BMI range?
According to the WHO, a BMI between 18.5 and 24.9 is considered normal weight. Below 18.5 is classified as underweight, 25.0-29.9 is overweight, 30.0-34.9 is obesity class I, 35.0-39.9 is obesity class II, and 40 or above is obesity class III. These thresholds apply to adults aged 18 and over.
Is BMI accurate for athletes or muscular people?
BMI does not distinguish between muscle and fat. Athletes or people with high muscle mass may have a high BMI while being perfectly healthy. In these cases, body-fat percentage, waist circumference, or a DEXA scan provides a more complete picture. BMI is best used as an initial screening tool, not a definitive diagnosis.
Does BMI apply to children and teenagers?
For children and teens (ages 2-19), BMI is interpreted using age- and sex-specific percentiles rather than the fixed adult categories. A pediatrician can plot your child's BMI on a growth chart to determine whether they fall in a healthy range for their age group.
How often should I check my BMI?
Weight changes gradually, so checking monthly is sufficient for most people. If you are actively working on weight loss or gain, bi-weekly checks can help you track trends. Focus on the long-term direction rather than day-to-day fluctuations.
What should I do if my BMI is outside the normal range?
If your BMI indicates you are underweight, overweight, or obese, consult a healthcare professional for a full assessment. They can evaluate body composition, lifestyle factors, and underlying conditions. Combining BMI with other metrics like waist-to-hip ratio and blood-panel results gives a much more accurate health picture.
Why Use Our Free BMI Calculator Online?
Our BMI Calculator gives you a quick, private check without an account. Enter your details and get an instant result. All processing happens locally, so we don't see or store your health-related inputs. For medical decisions, always consult a healthcare provider; this tool is for general guidance only.