Understanding Key Health & Fitness Metrics

This guide explains the essential concepts behind the calculators in our Health & Fitness section. Understanding these metrics can help you make informed decisions about your health, diet, and exercise routines.

Body Mass Index (BMI)

What it is: BMI is a simple numerical measure of a person’s weight in relation to their height. It's a widely used screening tool to categorize weight status (underweight, normal weight, overweight, or obesity) and identify potential weight problems.

How it's calculated:BMI = weight (kg) / [height (m)]²

Limitations: While useful, BMI is not a perfect measure. It doesn't distinguish between fat and muscle mass. As a result, very muscular individuals (like bodybuilders) might have a high BMI but low body fat. It should be used as a general guideline, not a diagnostic tool.

Basal Metabolic Rate (BMR)

What it is: BMR is the number of calories your body needs to perform its most basic, life-sustaining functions at rest. This includes breathing, circulation, nutrient processing, and cell production. It's the minimum energy your body requires to stay alive.

How it's calculated: Our calculator uses the Mifflin-St Jeor equation, which is considered more accurate than the older Harris-Benedict equation.

• Men: BMR = 10 * weight (kg) + 6.25 * height (cm) - 5 * age (y) + 5
• Women: BMR = 10 * weight (kg) + 6.25 * height (cm) - 5 * age (y) - 161

Your BMR is the starting point for determining your Total Daily Energy Expenditure (TDEE), which is your total daily calorie needs when activity level is factored in.

Body Fat Percentage (U.S. Navy Method)

What it is: This is the proportion of your total body weight that is fat. It's often considered a better indicator of health than weight alone, as it distinguishes fat from lean body mass.

How it's calculated: The U.S. Navy method uses body circumference measurements (neck, waist, and hips for women) to estimate body fat. It's a convenient and cost-effective method, though less accurate than clinical methods like DEXA scans. The formulas are based on logarithmic relationships between these measurements and body density.

Ideal Body Weight Formulas

What it is: These formulas provide an estimated healthy weight range based on height and gender. They are not a one-size-fits-all solution but provide a general guideline.

How it's calculated: There are several popular formulas (Hamwi, Devine, Robinson, Miller), each developed based on different population studies. They typically start with a base weight for a 5-foot-tall person and add a certain number of pounds or kilograms for each additional inch of height. Our calculator shows you the results from several of these formulas to provide a balanced perspective.