Know your body by the numbers.
From body fat to calorie needs, from macro splits to hydration goals — calculate your full body composition in a few steps.
What is BMI?
BMI, or Body Mass Index, is a value calculated from your weight relative to your height. It is a screening measure widely used to classify underweight, normal range, overweight or obesity. However, since it does not distinguish between fat, muscle and bone mass, it cannot on its own precisely indicate your body fat percentage or overall health.
Looks simple, calculates deep.
Questions on your mind
No. BMI uses only height and weight; it does not separate fat from lean mass. Calxin’s body fat calculation instead estimates your body fat percentage from neck, waist and — when needed — hip measurements. Both results are estimates meant for guidance.
Calxin evaluates your measurements with widely used methods such as Mifflin–St Jeor and US Navy. When you enter your information correctly, you get a clear reference for your body composition, daily energy needs and goal. Results may vary depending on the measurement method and individual differences.
Calorie and basal metabolism calculations use Mifflin–St Jeor, switching to Katch–McArdle when body fat is entered. Body fat is estimated with a circumference-based formula; 1RM with the Epley and Brzycki formulas; and ideal weight with the Devine, Robinson and Miller formulas. Each tool’s formula is explained on its calculator page.
Choose your activity level based on your total daily movement, not just your workouts. Someone with a desk job who trains a few times a week may not need the same energy as someone doing physical work all day. If unsure, start one level lower and adjust based on how your weight changes.
No. Calxin is built for general information and calculation. Its results do not replace medical diagnosis, treatment or personalized nutrition and exercise advice. For decisions about your health, consult a qualified health professional.