You can estimate how many calories you burn by calculating your Total Daily Energy Expenditure (TDEE), which accounts for your Basal Metabolic Rate (BMR) plus physical activity. Here's how it works:

Step 1: Calculate Basal Metabolic Rate (BMR)

BMR is the number of calories your body needs to maintain basic physiological functions at rest, like breathing and organ function. It depends on factors such as age, sex, weight, and height. Common formulas to calculate BMR include:

• Harris-Benedict Formula
  For men:
  (9.65×weight in kg)+(573×height in m)−(5.08×age in years)+260(9.65\times \text{weight in kg})+(573\times \text{height in m})-(5.08\times \text{age in years})+260(9.65×weight in kg)+(573×height in m)−(5.08×age in years)+260
  For women:
  (7.38×weight in kg)+(607×height in m)−(2.31×age in years)+43(7.38\times \text{weight in kg})+(607\times \text{height in m})-(2.31\times \text{age in years})+43(7.38×weight in kg)+(607×height in m)−(2.31×age in years)+43

• Mifflin-St Jeor Equation (considered accurate for many people)

• Katch-McArdle Formula (uses lean body mass, good for lean individuals)

Calculators online can help you apply these formulas easily

Step 2: Adjust for Activity Level

Since BMR only accounts for calories burned at rest, multiply your BMR by an activity factor to estimate total calories burned per day:

• 1.2 for sedentary (little or no exercise)
• 1.37 for lightly active (light exercise 1–3 days/week)
• 1.55 for moderately active (moderate exercise 3–5 days/week)
• 1.725 for very active (hard exercise 6–7 days/week)
• 1.9 for extra active (very physically demanding job or intense training)

This gives your Total Daily Energy Expenditure (TDEE), the estimated calories you burn daily

Additional Methods and Factors

• Heart rate monitors and activity trackers can estimate calories burned during exercise by measuring effort, but accuracy varies

• Indirect calorimetry (measuring oxygen consumption and CO2 output during activity) is the most precise scientific method but requires specialized equipment

• Factors affecting calorie burn include body weight (heavier people burn more calories), muscle mass (muscle burns more calories than fat), exercise intensity, age, sex, and body composition

Summary

To know how many calories you burn:

1. Calculate your BMR using a formula based on your personal stats.
2. Multiply your BMR by an activity factor that matches your daily activity level.
3. Optionally, use wearable devices or professional testing for more precise estimates.

This approach helps you understand your calorie needs for maintaining, losing, or gaining weight