Fitness Calculators

How They Work

BMI (Body Mass Index): A simple screening tool that estimates body fat based on your height and weight. While useful for general populations, it doesn't account for muscle mass.

Waist-to-Hip Ratio: Compares waist and hip circumference to estimate where you store body fat. Higher ratios can indicate more abdominal fat, which is linked to increased health risks even at a normal weight.

BMR (Basal Metabolic Rate): The calories your body burns at rest. By default we use the Mifflin-St Jeor equation. If you enter body fat %, we automatically switch to Katch-McArdle, which is more accurate for lean or muscular individuals.

TDEE (Total Daily Energy Expenditure): Your estimated daily calorie burn including activity. We multiply your BMR by an activity multiplier, then adjust for your goal-lose weight, maintain, or gain muscle-to give you a daily calorie target.

Macro Split: Converts your calorie target into daily protein, carb, and fat grams. By default that target comes from the TDEE estimate above; you can also enter your own calories. Pick a distribution preset (balanced, low-fat, low-carb, or high-protein) shaped around the Acceptable Macronutrient Distribution Ranges (AMDR)-about 45-65% carbs, 10-35% protein, and 20-35% fat-so splits stay flexible without extreme restriction. We translate your chosen percentages into grams with standard energy factors (4 kcal/g for protein and carbs, 9 kcal/g for fat).

Target Heart Rate: Helps you identify the right exercise intensity for your goals. Using your age (and optionally your resting heart rate), we estimate max heart rate and map light, moderate, and vigorous targets plus finer training zones. The talk test-whether you can hold a conversation-is a practical alternative when you are not wearing a monitor.

Daily Hydration: Applies CDC and Mayo Clinic total-fluid references by biological sex, with day-type tips for rest and exercise days. Targets include all beverages and food moisture, not plain water alone.