Your body burns calories around the clock, and the total number depends on a combination of your size, body composition, daily movement, and what you eat. Most people burn somewhere between 1,500 and 2,500 calories a day, though the range extends well beyond that in both directions. Finding your personal number involves understanding the different components of your daily calorie burn and choosing the right method to estimate each one.
The Four Components of Your Daily Calorie Burn
Your total daily energy expenditure isn’t one single process. It breaks down into four distinct categories, and knowing what they are helps you understand why two people of similar size can burn very different amounts.
Resting metabolism accounts for 60 to 70 percent of your total calorie burn. This is the energy your body uses just to stay alive: pumping blood, breathing, maintaining body temperature, running your brain. Even if you lay in bed all day, this baseline cost would still be substantial.
The thermic effect of food makes up roughly 10 percent of your daily burn. Digesting, absorbing, and processing food costs energy. Protein is the most expensive to process, requiring 20 to 30 percent of its calories just to digest. Carbohydrates cost 5 to 10 percent, and fat costs almost nothing at 0 to 3 percent. This is one reason high-protein diets nudge your total calorie burn slightly higher.
Non-exercise activity covers everything you do that isn’t deliberate exercise: walking to your car, fidgeting, cooking, standing at your desk, carrying groceries. This category varies enormously between people. Research comparing lean and obese sedentary individuals found that the leaner group spent about two more hours per day on their feet, translating to roughly 350 extra calories burned daily from these small movements alone.
Exercise is the smallest and most variable component for most people. A 30-minute brisk walk or a gym session might burn 150 to 400 calories depending on intensity and your body size, but unless you’re training for hours, it typically contributes less to your total burn than your resting metabolism does.
Estimate Your Resting Metabolism With a Formula
The most common starting point is a predictive equation called the Mifflin-St Jeor formula. A systematic review comparing multiple equations found it was the most reliable, predicting resting metabolic rate within 10 percent of the actual measured value in more people (both normal weight and obese) than any competing formula.
Here’s how it works:
- 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
For a 35-year-old woman who weighs 70 kg (154 lbs) and stands 165 cm (5’5″), the calculation gives roughly 1,399 calories per day at rest. That’s before any movement or food digestion is factored in.
To convert pounds to kilograms, divide by 2.2. To convert inches to centimeters, multiply by 2.54.
Scale Up to Your Total Daily Burn
Once you have your resting number, multiply it by an activity factor to estimate your full day’s calorie burn:
- Sedentary (desk job, little movement): multiply by 1.2
- Lightly active (some walking, light exercise 1 to 3 days/week): multiply by 1.375
- Moderately active (exercise 3 to 5 days/week): multiply by 1.55
- Very active (hard exercise 6 to 7 days/week): multiply by 1.725
- Extremely active (physical job plus intense training): multiply by 1.9
Using the example above, that 35-year-old woman with a resting rate of 1,399 who exercises moderately would multiply by 1.55, landing at about 2,168 calories per day. This is a useful ballpark, not a precise measurement. Most people overestimate their activity level, so if you’re unsure between two categories, choose the lower one.
Use MET Values for Specific Activities
If you want to calculate how many calories a particular workout or activity burns, MET values (metabolic equivalents) give you a more granular tool. One MET equals the energy you burn sitting still. An activity rated at 5 METs burns five times that amount.
The formula is: calories burned = METs × weight in kg × hours.
Some common MET values from the research compendium used by exercise scientists:
- Walking at a moderate pace (3 mph): 3.5 METs
- Brisk walking (3.5 mph): 4.3 METs
- Very brisk walking (4 mph): 5.0 METs
- Weight training, moderate effort (8 to 15 reps): 3.5 METs
- Weight training, vigorous effort: 6.0 METs
- Circuit training, vigorous intensity: 8.0 METs
So a 70 kg person doing 45 minutes of brisk walking would burn roughly 4.3 × 70 × 0.75 = 226 calories. This method is more accurate than the generic “calories burned” displays on gym equipment, which don’t account for your actual body composition.
How Accurate Are Fitness Trackers?
Wrist-worn devices like Apple Watch, Fitbit, and Garmin are popular for tracking calorie burn, but their accuracy for energy expenditure is poor. A systematic review of wearable devices found that the average error rate for calorie estimates exceeded 30 percent across all brands tested. None of the devices proved accurate for measuring energy expenditure.
That 30 percent error works in both directions. A tracker might tell you that you burned 500 calories during a workout when the real number was 350, or it might undercount on a day filled with housework and errands. Wearables are better at tracking trends over time (are you moving more this week than last?) than giving you a reliable daily number. If you’re using one to guide how much you eat, build in a healthy margin of skepticism.
The Gold Standard: Indirect Calorimetry
If you want the most precise measurement of your resting metabolism, some clinics, hospitals, and sports performance centers offer a test called indirect calorimetry. You breathe into a device for 10 to 20 minutes while it analyzes the ratio of oxygen you inhale to carbon dioxide you exhale. Because your body produces carbon dioxide in proportion to the fuel it burns, this gas exchange reveals your actual metabolic rate rather than an estimate.
This is considered the clinical gold standard, and it’s especially useful if formula-based estimates haven’t matched your real-world experience with weight gain or loss. The test typically costs $75 to $250 out of pocket and isn’t covered by most insurance plans unless it’s medically necessary.
What Actually Changes Your Calorie Burn
Body composition matters more than body weight alone. Each kilogram of muscle (about 2.2 pounds) burns roughly 24 additional calories per day at rest. Fat tissue, by contrast, contributes very little to resting metabolism. This is why two people who weigh the same can have meaningfully different metabolic rates if one carries more muscle.
Age matters less than most people think. A large-scale study published in Science found that metabolic rate stays remarkably stable between ages 20 and 60 after accounting for changes in body composition. The common belief that metabolism tanks in your 30s or 40s doesn’t hold up. What changes is that people tend to lose muscle and gain fat gradually, and they often move less as they age. The metabolism itself isn’t slowing down during those decades.
Daily movement outside of exercise has a surprisingly large impact. The difference between a sedentary person and someone who walks frequently, stands more, and stays generally active throughout the day can easily be 300 to 350 calories, comparable to a moderate gym session. If your goal is to increase your total burn, adding more movement to your day (parking farther away, taking calls while walking, standing during tasks) can be just as effective as adding formal workouts.
A Practical Approach to Finding Your Number
Start with the Mifflin-St Jeor formula and an honest activity multiplier. Track your weight and food intake for two to three weeks without changing your habits. If your weight stays stable, you’re eating close to your total daily burn, and you’ve found your maintenance number through real-world data. If you’re gaining or losing, adjust: roughly 3,500 calories equals one pound of body weight, so a gain of half a pound per week means you’re eating about 250 calories above your daily burn.
This combination of calculation and observation is more reliable than any single method alone. The formula gives you a starting estimate, your body’s response over a few weeks gives you the correction, and MET values help you understand how individual activities contribute to the total picture.