BMI calculator

Your Body Mass Index (BMI) is one of the simplest ways to understand whether your weight is in a healthy range for your height. RNfinity's free BMI Calculator helps you instantly check your BMI, giving you a clear idea of whether you're underweight, a healthy weight, overweight, or in the obese range. Using your height and weight, this calculator provides a science-based estimate that can guide your nutrition, fitness, and overall health decisions.

Our BMI calculator is suitable for both men and women, using the same proven formula trusted by health professionals and based on WHO and CDC guidelines. Whether you're just starting your fitness journey, managing weight, or tracking progress toward a goal, this tool gives you fast, accurate insights into your current health status.

Body Mass Index (BMI) is calculated by dividing your weight in kilograms by your height in meters squared (kg/m²):

$\mathrm{BMI}=\frac{\mathrm{weight\; (kg)}}{{\mathrm{height\; (m)}}^2}$

This value estimates body fat relative to height and weight. While it doesn't directly measure fat, BMI is widely used by healthcare professionals as a screening tool for weight-related health risks.

Our online calculator handles the math instantly — just enter your height and weight, and it returns your BMI along with your classification based on official BMI charts for men and women.

The general BMI ranges are:

You can explore our BMI chart for women or BMI chart for men for visual guidance and comparison.

A BMI above or below the healthy range may indicate an increased risk of health conditions such as heart disease, diabetes, or undernutrition. Consult a healthcare professional for personalized guidance.

Knowing your BMI helps you make informed lifestyle choices. A high BMI may suggest adjusting diet or activity levels, while a low BMI could indicate the need to gain weight for better health.

This tool also doubles as a body mass calculator and body weight index calculator, helping you monitor progress over time and set realistic goals.

While BMI is useful, it is not a perfect measure of body composition. Muscle mass, bone density, age, and sex can influence results. RNfinity links this BMI calculator with other tools — such as our calorie calculator, protein calculator, and TDEE calculator — giving you a complete picture of your body’s nutritional and energy needs.