How It Works

Understanding how TDEE-Calc.com calculates your energy needs can help you make informed decisions about your nutrition and fitness goals. This guide walks you through the process step-by-step.

What is TDEE?

TDEE stands for Total Daily Energy Expenditure—the total number of calories your body burns in a 24-hour period. This includes:

1. Basal Metabolic Rate (BMR): Calories burned at complete rest to maintain basic bodily functions
2. Non-Exercise Activity Thermogenesis (NEAT): Calories burned through daily activities and unconscious movement
3. Exercise Activity Thermogenesis (EAT): Calories burned during intentional exercise
4. Thermic Effect of Food (TEF): Calories burned digesting and processing food

The Calculation Process

Step 1: Calculate Your BMR

Your Basal Metabolic Rate is the foundation of all TDEE calculations. This represents the minimum calories your body needs to function at rest—breathing, circulating blood, regulating temperature, and maintaining cellular processes.

The calculator offers three formulas:

Mifflin-St Jeor (Default & Recommended)

• Most accurate for the general population
• Based on weight, height, age, and sex
• Validated by extensive research since 1990

Katch-McArdle (For Lean Individuals)

• Most accurate when you have reliable body fat measurements
• Based on lean body mass instead of total weight
• Best for athletic individuals with professionally measured body composition

Harris-Benedict (Legacy)

• Older formula from 1919, revised in 1984
• Included for comparison with older research or clinical protocols
• Generally less accurate than Mifflin-St Jeor

Example calculation using Mifflin-St Jeor:

For a 30-year-old man, 180 cm tall, weighing 80 kg:

BMR = (10 × 80) + (6.25 × 180) - (5 × 30) + 5
BMR = 800 + 1,125 - 150 + 5
BMR = 1,780 calories/day

Step 2: Apply Activity Multiplier

Your BMR is then multiplied by an activity factor to account for your daily movement and exercise:

Continuing the example:

TDEE = BMR × Activity Factor
TDEE = 1,780 × 1.375 (lightly active)
TDEE = 2,447 calories/day

This person burns approximately 2,447 calories per day maintaining their current weight.

Step 3: Set Your Goal

Once you know your TDEE, you can create a calorie target based on your goal:

Fat Loss

• Small deficit: TDEE - 250-300 calories (0.25 kg / 0.5 lb per week)
• Moderate deficit: TDEE - 500 calories (0.5 kg / 1 lb per week)
• Aggressive deficit: TDEE - 750-1,000 calories (0.75-1 kg / 1.5-2 lbs per week)

Muscle Gain

• Small surplus: TDEE + 200-300 calories (minimize fat gain)
• Moderate surplus: TDEE + 300-500 calories (balanced approach)

Maintenance

• Eat at your TDEE

Important: Larger deficits aren't always better. Excessively aggressive deficits (>1,000 calories) can lead to:

• Excessive muscle loss
• Metabolic adaptation
• Hormonal disruptions
• Unsustainable hunger and cravings
• Decreased training performance

Step 4: Calculate Macronutrients

With your calorie target set, the calculator distributes those calories across three macronutrients:

Protein (4 calories per gram)

• Calculated based on your weight, activity level, and goal
• Ranges from 1.6-2.7 g per kg body weight
• Higher when cutting, lower when maintaining or bulking

Fats (9 calories per gram)

• Minimum levels set for hormonal health
• Men: ~0.4-0.6 g/kg minimum
• Women: ~0.6-0.8 g/kg minimum
• Remainder allocated based on diet style preference

Carbohydrates (4 calories per gram)

• Fills remaining calories after protein and fat are set
• Can be adjusted up or down based on diet preference
• Higher for athletic training, lower for ketogenic approaches

Example macro calculation (continuing our example):

Goal: Moderate fat loss (TDEE - 500 = 1,950 calories/day)

• Protein: 160g (640 calories) - 2.0 g/kg for muscle preservation
• Fat: 65g (585 calories) - 0.8 g/kg for health
• Carbs: 181g (725 calories) - remaining calories

Understanding the Results

Your Dashboard Shows:

BMR

• The baseline calories your body burns at rest
• This is the minimum you should eat for extended periods

TDEE

• Your total daily calorie burn including all activity
• Eat at this level to maintain current weight

Calorie Target

• Adjusted based on your goal (deficit, surplus, or maintenance)
• This is your daily eating target

Macros

• Protein, carb, and fat targets in grams
• Supports your goal while maintaining health

Estimated Timeline

• How long it will take to reach your goal weight
• Based on your chosen deficit/surplus
• Assumes consistent adherence

Why Your TDEE Isn't Fixed

Your TDEE changes over time due to several factors:

Weight Changes

• As you lose weight, your TDEE decreases (less mass to maintain)
• As you gain weight, your TDEE increases

Body Composition Changes

• Muscle burns more calories than fat
• Gaining muscle increases TDEE
• Losing muscle decreases TDEE

Activity Changes

• More daily steps = higher TDEE
• New exercise routine = higher TDEE
• Becoming sedentary = lower TDEE

Metabolic Adaptation

• Extended dieting can lower metabolic rate by 5-15%
• This is why "diet breaks" can be beneficial
• Reverse dieting after a cut helps restore metabolism

Age

• Metabolism naturally slows with age
• Primarily due to muscle loss and reduced activity
• Can be partially offset with strength training

How to Use Your Results

Week 1-2: Establish Your Baseline

1. Eat at your calculated calorie target
2. Track your weight daily (same time, same conditions)
3. Calculate weekly averages to smooth out daily fluctuations
4. Monitor energy and performance in your workouts

Week 3-4: Assess and Adjust

Compare your actual results to predictions:

If losing faster than expected:

• Increase calories by 100-200/day
• You may have overestimated TDEE or are too aggressive

If losing slower than expected:

• Decrease calories by 100-200/day
• You may have underestimated TDEE or need a larger deficit

If gaining too much fat:

• Reduce surplus by 100-200 calories
• Consider increasing protein slightly

If not gaining muscle:

• Ensure you're in a surplus
• Check protein intake is adequate
• Verify training intensity is sufficient

Ongoing: Monitor and Refine

• Recalculate every 5-10 lbs lost/gained
• Adjust activity multiplier if your routine changes
• Take diet breaks if dieting for extended periods (8+ weeks)
• Trust the process - weight loss isn't linear, look at 2-4 week trends

Common Questions

Q: Why is my calculated TDEE different from other calculators?

Different calculators use different formulas and activity multipliers. Small variations (100-200 calories) are normal and insignificant. Use your calculator of choice consistently and adjust based on real-world results.

Q: Should I eat back exercise calories?

If you've set your activity level correctly, your TDEE already accounts for exercise. Don't add extra calories for individual workouts unless your activity level changes significantly.

Q: My weight isn't changing even though I'm in a deficit. What's wrong?

Give it 2-4 weeks. Daily weight fluctuates from water retention, food volume, hormones, and stress. If truly no change after 4 weeks, reduce calories by 10-15% or increase activity.

Q: Can I trust the timeline predictions?

Timeline predictions assume perfect adherence and linear progress. Real-world fat loss includes plateaus, water retention fluctuations, and occasional higher calorie days. Use timelines as rough guides, not rigid schedules.

Q: How often should I recalculate my TDEE?

Recalculate every 5-10 lbs of weight change, when changing activity levels significantly, or if your progress stalls for 3-4 weeks.

The Most Important Principle

Calculated TDEE is a starting point, not gospel.

Your actual TDEE depends on factors no formula can perfectly capture: genetics, metabolic history, hormone levels, NEAT, and more. The calculator provides an evidence-based estimate, but your real-world results provide the truth.

Use the calculation to establish a baseline, then become a scientist with your own body:

1. Start with the calculated target
2. Track consistently for 2-4 weeks
3. Compare results to predictions
4. Adjust based on data
5. Repeat

This process of calculation, tracking, and adjustment is how you'll discover your true TDEE and optimize your nutrition for your specific body and goals.

Next Steps

Ready to put this knowledge into action?

• Start with the Wizard - Get personalized recommendations through guided setup
• Use the Calculator - Input your stats and get immediate results
• Learn About Formulas - Deep dive into BMR calculation methods
• Explore Macro Options - Understand different diet approaches
• Read the FAQ - Get answers to common questions

The best time to start tracking your TDEE and taking control of your nutrition was years ago. The second-best time is right now.