Free Body Fat, Nutrition & Fitness Tools

FatCalc offers a comprehensive suite of free calculators to help you understand your body and make informed health decisions. Whether you’re tracking body composition, planning your nutrition, assessing cardiovascular fitness, or setting training goals, our tools are built on validated formulas and research-backed methods to provide accurate, personalized estimates. Click any calculator link below to get started or take a Health and Nutrition quiz powered by AI. Take the quiz.link

If you’re trying to lose weight, it’s important to know what that weight is made of—mainly fat, stored as adipose tissue.

Adipose tissue is made up of cells called adipocytes, each containing a big fat droplet. This storage part of the cell, known as a ‘lipid droplet,’ is mostly composed of triglycerides—three fatty acids linked to glycerol, which is a type of alcohol found in fats. When you lose weight, these triglycerides are what your body uses up.

Body composition includes not just fat but also lean mass, such as muscle, bones, organs, and water. The balance between fat mass and lean mass tells you far more about health than body weight alone. Tracking body fat percentage and muscle mass offers better insights than simply watching the scale.

Your body burns calories even at rest, called Basal Metabolic Rate (BMR) or the closely related Resting Metabolic Rate (RMR). These numbers show the amount of calories needed for basic life functions, such as breathing and cell repair.

Your Total Daily Energy Expenditure (TDEE) is the amount of calories you burn each day from life functions, movement, exercising, and even digesting food. Tracking your TDEE makes it easier to reach your goals, whether that’s losing fat, maintaining your current weight, or building muscle. Creating a small calorie deficit (eating fewer calories than your TDEE) supports fat loss, while eating more than your TDEE with resistance training can help you gain muscle.

Calories only measure energy. The three main macronutrients—protein, carbohydrates, and fats—have unique roles. Protein builds and repairs muscle, especially during calorie deficits or intense training. Carbohydrates fuel high-intensity activity, and fats produce hormones, aid nutrient absorption, and keep cells healthy.

Don’t forget hydration. Water is essential for almost every process in your body. How much you need depends on your size, activity, and climate. Staying hydrated boosts exercise performance, cognitive function, and overall well-being.