Your maintenance calories are the number of calories you burn in a full day, including everything from breathing to walking to digesting food. The simplest way to estimate this number is to multiply your current weight in pounds by 15, which gives a rough maintenance figure for someone who’s moderately active. For a more precise answer, you’ll want to calculate your resting metabolic rate using a formula, then multiply it by an activity factor that reflects how much you move throughout the day.
What Makes Up Your Daily Calorie Burn
Your total daily energy expenditure (TDEE) has three components. The largest is your resting metabolic rate, which is the energy your body uses just to stay alive: pumping blood, breathing, maintaining body temperature, and keeping your organs running. This accounts for roughly 60 to 70 percent of your total burn. The second component is physical activity, both structured exercise and all the smaller movements you make throughout the day like fidgeting, standing, and walking around your house. The third is the thermic effect of food, the energy it takes to digest, absorb, and transport nutrients, which accounts for about 10 percent of your daily total. If you eat 2,000 calories, roughly 200 of those go toward processing that food.
The physical activity component is where individual variation gets dramatic. Non-exercise activity thermogenesis, the calories you burn from all movement that isn’t deliberate exercise, can differ by up to 2,000 calories per day between two people of similar size. Someone with an active job who’s on their feet all day burns far more than someone who sits at a desk, even if neither person sets foot in a gym. This is why formulas can only get you in the ballpark.
Step 1: Estimate Your Resting Metabolic Rate
Two formulas are widely used to estimate how many calories your body burns at rest. Both require your weight, height, age, and sex.
The Mifflin-St Jeor Equation
For men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
For women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161
The Harris-Benedict Equation
For men: 66.5 + (13.75 × weight in kg) + (5.003 × height in cm) − (6.755 × age)
For women: 655.1 + (9.563 × weight in kg) + (1.850 × height in cm) − (4.676 × age)
Neither formula is dramatically more accurate than the other. A study comparing prediction equations found that both the Mifflin-St Jeor and Harris-Benedict equations predicted resting metabolic rate within 10 percent of the measured value for only about 56 to 58 percent of participants. That means for roughly 4 in 10 people, the estimate is off by more than 10 percent. The Harris-Benedict equation tends to overestimate for younger adults (18 to 29), while Mifflin-St Jeor tends to underestimate for people who are normal weight, those aged 40 to 60, and white participants.
To convert pounds to kilograms, divide by 2.2. To convert inches to centimeters, multiply by 2.54.
Step 2: Multiply by Your Activity Level
Once you have your resting metabolic rate, multiply it by an activity factor to estimate your full daily burn:
- Sedentary (desk job, little movement): multiply by 1.2
- Lightly active (light exercise 1 to 3 days per week): multiply by 1.375
- Moderately active (exercise 3 to 5 days per week): multiply by 1.55
- Very active (hard exercise 6 to 7 days per week): multiply by 1.725
- Extra active (intense daily training or physical job plus exercise): multiply by 1.9
Most people overestimate their activity level. If you work at a desk and exercise three times a week for 30 to 45 minutes, “lightly active” is probably more honest than “moderately active.” Harvard Health defines moderately active as getting at least 30 minutes of brisk physical activity every day, not just a few times a week.
A Quick Example
A 35-year-old woman who weighs 150 pounds (68 kg) and stands 5’6″ (167.6 cm) would calculate her resting metabolic rate using Mifflin-St Jeor as: (10 × 68) + (6.25 × 167.6) − (5 × 35) − 161 = 680 + 1,047.5 − 175 − 161 = 1,391.5 calories. If she’s lightly active, her estimated TDEE is 1,391.5 × 1.375 = roughly 1,913 calories per day.
The Katch-McArdle Option for Leaner or Heavier Bodies
Standard formulas use total body weight, which means they don’t distinguish between muscle and fat. Two people who weigh 200 pounds will get the same result even if one is 15 percent body fat and the other is 35 percent. Since muscle tissue burns significantly more energy at rest than fat tissue, this matters.
If you know your body fat percentage (from a DEXA scan, skinfold calipers, or even a reasonable estimate), the Katch-McArdle formula adjusts for this. First, calculate your lean body mass: total weight minus (total weight × body fat percentage as a decimal). For example, if you weigh 80 kg at 20 percent body fat: 80 − (80 × 0.20) = 64 kg of lean mass. Then plug that into the formula: 370 + (21.6 × lean body mass in kg). For that example: 370 + (21.6 × 64) = 1,752 calories at rest. From there, you apply the same activity multipliers.
This formula is particularly useful if you carry more muscle than average or if your body fat is significantly above or below the typical range, since it corrects for what standard formulas miss.
Why Tracking Beats Formulas
Every formula is an estimate, and a 10 percent error on a 2,000-calorie estimate means you could be off by 200 calories in either direction. The most reliable way to find your actual maintenance calories is to track what you eat and what you weigh over two to three weeks.
Here’s how to do it. For 14 to 21 days, weigh yourself every morning under consistent conditions (after using the bathroom, before eating) and log everything you eat as accurately as you can, using a food scale when possible. At the end of that period, calculate your average daily intake and compare it to your weight trend. If your weight stayed essentially flat (within a pound or so of where you started), your average daily intake is very close to your maintenance calories. If you lost weight, your maintenance is higher than what you ate. If you gained, it’s lower.
This approach accounts for all the individual variables that formulas can’t capture: your specific metabolism, your fidgeting habits, your digestion, your job, and the thousand small movements that add up throughout a day. It takes patience, but it gives you a personalized number rather than a population average.
Common Reasons Estimates Go Wrong
The biggest source of error isn’t usually the formula. It’s the activity multiplier. People tend to mentally round up their activity level, categorizing themselves as “moderately active” when their daily step count and actual exercise frequency put them closer to “lightly active.” If your calculated maintenance seems too high (you’re gaining weight eating at that number), drop one activity tier and reassess.
Calorie tracking errors are the other major culprit. Cooking oils, condiments, beverages, and the difference between a “tablespoon” of peanut butter and what you actually put on your toast can easily add 200 to 400 uncounted calories per day. If you’re using the tracking method, accuracy in logging matters more than precision in the formula.
Your maintenance number also isn’t fixed. It shifts with changes in weight, age, muscle mass, hormonal status, and even the season. Recalculating every few months, or whenever your weight changes by more than 5 to 10 pounds, keeps your estimate current.