BMI Weight Loss Calculator

Body Mass Index (BMI) evaluates your body mass relative to your height squared, using the metric formula BMI = mass / height² (where mass is in kilograms and height is in meters). To find your target mass for a specific BMI goal, the equation reverses to Target Mass = Target BMI × Height². The difference between your current mass and this target mass gives you your required weight loss or gain. Additionally, the tool calculates your BMI Prime—a ratio comparing your current BMI to the upper limit of the normal weight threshold (25)—offering a quick percentage-based view of how far you are from standard health markers.

Imagine an adult with a current mass of 90 kg and a height of 1.75 meters, aiming for a normal, healthy BMI of 22. First, we square the height: 1.75² = 3.0625. Next, we multiply this squared height by the target BMI: 22 × 3.0625 = 67.375 kg. Subtracting this target mass from the current mass (90 - 67.375) results in a required weight loss of approximately 22.63 kg to reach a BMI of 22. Furthermore, their initial BMI would be 90 / 3.0625 = 29.38, placing them in the overweight category with a BMI Prime of 1.17.

When pursuing a target BMI, focus on gradual, sustainable lifestyle adjustments rather than rapid restriction. Aim for a weekly weight loss of 0.5 to 1 kg, which preserves lean muscle mass. Remember that standard BMI does not distinguish between muscle and fat mass; if you are an avid strength trainer, your muscle density may artificially elevate your BMI into the overweight range even with low body fat. Always consult a healthcare professional before embarking on significant caloric deficits.