BMI, daily calories, water intake, sleep cycles, body fat percentage — all in one place. Free forever.
Calculate your Body Mass Index and find your healthy weight range
Find your Total Daily Energy Expenditure and calorie goal
Find your daily hydration goal based on weight and activity
Find the best times to wake up or fall asleep to feel refreshed
Estimate body fat % using the US Navy method (neck + waist + hip)
Get your daily protein, carbs and fat targets based on your goal
See your ideal weight range using 4 different scientific formulas
FreeBodyCalc is a free collection of online health and fitness calculators. Our tools use established scientific formulas to give you useful estimates about your body and health needs. All calculations happen instantly in your browser — we never store your data.
Body Mass Index (BMI) is calculated by dividing your weight in kilograms by the square of your height in meters. While BMI doesn't account for muscle mass or body composition, it remains one of the most widely used screening tools for identifying potential weight-related health concerns.
Our calorie calculator uses the Mifflin-St Jeor equation, widely regarded as the most accurate formula for estimating Basal Metabolic Rate (BMR). Your TDEE (Total Daily Energy Expenditure) is then calculated by multiplying BMR by your activity factor, giving you the number of calories you need to maintain, lose, or gain weight.
Proper hydration is essential for virtually every function in the body, from regulating temperature to lubricating joints and supporting digestion. The recommended daily water intake varies based on weight, activity level, and climate. Our calculator provides a personalized estimate using current hydration research guidelines.
The human sleep cycle lasts approximately 90 minutes and includes both REM and non-REM stages. Waking up mid-cycle often causes grogginess (sleep inertia), while waking between cycles feels more natural. Our sleep calculator helps you find optimal bedtimes or wake-up times aligned with your natural sleep cycles.
Our body fat calculator uses the US Navy circumference method, which estimates body fat percentage based on height, neck, and waist measurements (and hip for women). While DEXA scans remain the gold standard for body composition analysis, this method provides a reasonable estimate without equipment.
Macronutrients — protein, carbohydrates, and fat — are the three main types of nutrients that provide energy. The optimal balance depends on your goal. Fat loss typically benefits from higher protein, muscle gain from higher carbohydrates, and ketogenic diets from very high fat. Our macro calculator adjusts the ratios based on your selected goal.