Fitness & Health

TDEE, BMI, 1RM strength, sleep & wellness trackers.

Energy Outputs Calculator

Use this free Energy Outputs Calculator to run instant, privacy-first client-side calculations.

Target Daily Calories
2,763
Maintenance (Weight Stable)

Energy Expenditure

BMR (Coma)
1,783
TDEE (Active)
2,763
Target Daily Calories
2,763
Maintenance · Balanced Split

Macronutrient Split

Protein (g)
207
Carbs (g)
242
Fats (g)
107
Expert Reviewed for 2026

The Ultimate Guide to Health & Fitness Mathematics

Master the mathematics of the human body. From calculating exact TDEE (Total Daily Energy Expenditure) and understanding your Karvonen training zones, to analyzing advanced body composition metrics and optimizing your REM sleep cycles for maximum recovery.

Basal Metabolic Rate (BMR)

Your BMR represents the absolute minimum number of calories your body requires to function at complete rest. Think of it as the energy required to simply exist in a coma. We calculate this using the highly accurate Mifflin-St Jeor equation.

Clinical studies have proven this formula to be the most reliable for modern body types, as it properly accounts for lean mass distribution.

Total Daily Energy Expenditure

Your TDEE scales your BMR by your physical activity level. This is the exact number of calories you burn on a daily basis.

  • Fat Loss: You must create a caloric deficit below your TDEE. (e.g. -500 calories/day)
  • Maintenance: Consume exactly your TDEE to remain weight stable.
  • Muscle Gain: Consume a slight surplus above your TDEE to fuel hypertrophy.

The Mathematics of Macronutrients

While your total calories dictate whether you lose or gain weight, your macronutrient split dictates what kind of weight you lose or gain.

Protein (4 kcal/g) Essential for muscle synthesis and repair. High protein diets increase satiety.
Carbohydrates (4 kcal/g) The body's preferred and most efficient energy source for intense training.
Fats (9 kcal/g) Vital for hormone regulation, nutrient absorption, and cognitive function.

Dietary fat does not inherently make you fat; exceeding your total caloric limit does. A balanced macro split ensures you retain muscle mass while effectively losing body fat.

The Flaw of BMI

Body Mass Index (BMI) is a useful statistical tool for large populations, but it has a major flaw for individuals: it cannot distinguish between fat and muscle.

Highly trained athletes often fall into the "Overweight" or "Obese" categories simply because muscle is vastly denser than adipose tissue (fat).

The Navy Method

The U.S. Navy Body Fat Formula provides a far more accurate picture of your actual health.

By measuring your circumferences (neck, waist, and hip) against your height, the formula estimates your true body fat percentage and lean body mass with a high degree of clinical precision.

Training Optimization

The Karvonen Formula

Traditional heart rate zones only use your age (220 - Age). The Karvonen Formula is superior because it factors in your Resting Heart Rate (RHR). This creates personalized training zones that adapt as your cardiovascular fitness improves.

Safe 1RM Estimation

Testing an absolute 1 Rep Max is highly taxing and dangerous. We use scientifically validated coefficients (the Brzycki and Epley equations) to accurately estimate your 1RM based on sub-maximal lifts (e.g., a 5-rep set).

Sleep Cycles & Recovery

Sleep is not merely rest; it is an active state of physiological repair. The human brain cycles through distinct phases of sleep, culminating in REM. A complete cycle takes roughly 90 minutes. Waking up in the middle of a deep sleep phase results in severe sleep inertia (grogginess).

Our Sleep Cycle calculator works backward from your required wake-up time to find optimal bedtimes that align precisely with the end of a 90-minute cycle, ensuring you wake up feeling alert, refreshed, and recovered.

The Science of TDEE & Basal Metabolism

Your Total Daily Energy Expenditure (TDEE) is the absolute foundation of any body composition goal. It represents the total number of calories you burn in a given day, combining your Basal Metabolic Rate (BMR), the Thermic Effect of Food (TEF), and your Non-Exercise Activity Thermogenesis (NEAT).

The Mifflin-St Jeor Equation:

Widely considered by clinical dietitians as the most accurate predictive equation for modern adults:

  • Men: (10 × weight in kg) + (6.25 × height in cm) - (5 × age) + 5
  • Women: (10 × weight in kg) + (6.25 × height in cm) - (5 × age) - 161

Macronutrient Partitioning

While a caloric deficit guarantees weight loss, your macronutrient split (Protein, Fats, Carbohydrates) dictates what *kind* of weight you lose. To prioritize fat loss while preserving lean muscle mass during a cut, sports nutritionists recommend setting protein intake to roughly 0.8 - 1.2 grams per pound of body weight, filling the remaining calories with fats (hormonal health) and carbohydrates (glycogen replenishment).

Frequently Asked Questions

Nutrition & Macros

Should I track raw or cooked food weights?
Always weigh your food raw (uncooked). Cooking dramatically alters the water content of food?meat loses water and becomes lighter, while rice absorbs water and becomes heavier. Nutritional databases are almost exclusively calibrated for raw weights.
How large should my caloric deficit be for fat loss?
A healthy, sustainable deficit is between 300 to 500 calories below your TDEE. This yields about 0.5 to 1 pound of fat loss per week. Aggressive deficits (1000+ calories) inevitably lead to severe muscle catabolism, metabolic adaptation, and binge eating.

Training & Recovery

Does lifting weights stunt your growth?
No. This is a thoroughly debunked myth. Resistance training actually increases bone mineral density. The only risk to growth plates comes from acute injuries caused by poor form or excessive ego-lifting, not from the act of lifting weights itself.
Why do I wake up tired even after 8 hours of sleep?
You likely woke up in the middle of a deep sleep phase (Stage 3 or 4). It is far better to sleep for exactly 7.5 hours (five 90-minute cycles) and wake up at the end of a REM cycle than to sleep for 8 hours and wake up mid-cycle with sleep inertia.

Rate Fitness & Health

Help us improve by rating this tool.

4.8/5
154 reviews