About This Calculator

What is BMI? Body Mass Index (BMI) is a widely used screening tool that estimates body fat based on your weight and height. It is not a diagnostic measurement of body fat percentage or health, but it is an excellent starting point for understanding where your weight falls relative to established health guidelines.

How the WHO Categories Work This calculator uses the World Health Organization (WHO) BMI classification system, the global standard adopted by healthcare providers worldwide:

• Underweight: BMI below 18.5
• Normal weight: BMI 18.5 to 24.9
• Overweight: BMI 25 to 29.9
• Obese: BMI 30 or higher

These ranges are based on large-scale population health data and are used consistently across clinical settings to identify risk factors related to weight.

How We Calculate Your Healthy Weight Range Using the WHO “Normal” range (18.5–24.9), we reverse-calculate what your weight would need to be at your specific height to fall inside that bracket. This gives you a personalized, height-adjusted target zone rather than a generic number.

What is the Devine Formula? The Devine formula is a long-established equation used in medicine to estimate Ideal Body Weight (IBW). Unlike BMI, which only considers height and weight, Devine also accounts for biological sex because baseline lean mass differs between male and female physiology.

• For men: 50 kg + 2.3 kg for every inch over 5 feet
• For women: 45.5 kg + 2.3 kg for every inch over 5 feet

Because the Devine formula was designed for adults 5 feet and taller, the tool automatically displays your BMI healthy range instead if you are below that height threshold.

How This Tool Combines Both Rather than showing you a single “magic number,” this calculator gives you two useful reference points:

1. The BMI healthy weight range — a flexible zone where your risk profile aligns with the WHO “Normal” category.
2. The Devine target — a precise marker within that range representing the traditional medical ideal for your sex and height.

Seeing both together helps you understand not just where you are, but where the established standards suggest is a balanced place to be.

A Note on Accuracy All results are rounded to whole numbers for clarity. BMI is a screening tool, not a medical diagnosis. Muscle mass, bone density, age, and individual health conditions are not captured in BMI or the Devine formula. If you are an athlete, pregnant, or managing a health condition, please discuss your results with a healthcare professional.