Weight & Obesity
Understanding your weight in relation to your health involves more than a number on the scale. Our free weight and body composition tools help you understand measures like BMI, body fat, waist-to-hip ratio and ideal weight ranges — clearly and based on established methods. These are screening tools for education, not diagnoses; your doctor interprets what they mean for your individual health.
BMI Calculator
Calculate your Body Mass Index (BMI) to understand whether your weight is healthy for your height. Uses World Health Organization (WHO) classification standards.
Body Fat Percentage Calculator
Estimate your body fat percentage using the U.S. Navy circumference method — a practical measure of body composition that tells you more than weight alone.
Ideal Weight Calculator
Estimate your ideal body weight using four established medical formulas. A useful reference range based on your height and sex.
Waist-to-Hip Ratio Calculator
Calculate your waist-to-hip ratio — a simple measure of fat distribution that the World Health Organization uses to assess health risk.
Body Surface Area (BSA) Calculator
Calculate your body surface area using the Mosteller formula — a measure used in medicine for drug dosing, physiology and clinical assessment.
Child & Teen BMI Calculator
Calculate BMI for children and teenagers aged 2 to 19. Because children's bodies change with age, the result must be interpreted using percentile growth charts.
Waist-to-Height Ratio Calculator
Calculate your waist-to-height ratio — a simple, powerful indicator of health risk based on a straightforward rule: keep your waist under half your height.
Child & Teen BMI Percentile Calculator
Calculate your child or teenager's BMI and see their exact BMI-for-age percentile using official CDC growth charts. For ages 2 to 20.
Measures of healthy weight
Several measures help assess weight and body composition. Body Mass Index (BMI) uses height and weight to estimate whether you are in a healthy weight range, and is widely used for screening. Waist measurements and waist-to-hip ratio give insight into where fat is stored, as fat around the abdomen carries greater health risk. Body fat percentage estimates how much of your body is fat tissue.
Each measure has strengths and limitations. BMI, for example, does not distinguish muscle from fat, so a muscular person may have a high BMI despite low body fat. This is why these measures are best used together and interpreted in context, rather than relying on any single number to judge health.
Why weight matters for health
Carrying excess weight, particularly around the abdomen, is associated with a higher risk of several conditions, including type 2 diabetes, high blood pressure, heart disease and joint problems. Understanding your measures can help you and your doctor assess these risks and decide whether any changes would be beneficial.
At the same time, health is about much more than weight alone, and these tools are starting points for understanding, not judgements. Sustainable healthy habits — balanced eating, regular activity, good sleep and not smoking — benefit health across the board, regardless of the number on the scale.
Using these weight tools
Our weight and body composition tools include a BMI calculator, body fat calculator, ideal weight calculator, waist-to-hip and waist-to-height ratio calculators, and more. Each helps you understand a specific measure and where your value falls within general reference ranges.
These tools are educational screening measures, not diagnoses. If you have concerns about your weight or health, or would like personalised guidance, your doctor can interpret these measures in the context of your full health and advise on any steps that would help.
Frequently asked questions
What is a healthy BMI?
For adults, a BMI between 18.5 and 24.9 is generally considered a healthy weight range, 25 to 29.9 overweight, and 30 or above falls into the obesity range. However, BMI is a screening tool that does not distinguish muscle from fat, so it is interpreted alongside other measures and your overall health by a doctor.
Is BMI or waist measurement more important?
Both give useful but different information. BMI estimates overall weight status, while waist measurement and waist-to-hip ratio show where fat is stored — and abdominal fat carries greater health risk. Used together they give a fuller picture than either alone. Our tools let you check both, and a doctor interprets them in context.
Are these weight tools a diagnosis?
No. These are educational screening tools that use established methods to help you understand measures like BMI and body fat. They do not diagnose any condition. Your doctor interprets what these measures mean for your individual health, considering your full situation, and can advise on any steps that would be beneficial.