Your maintenance calories are the total number of calories you burn in a day, often called your Total Daily Energy Expenditure (TDEE). The most reliable way to estimate this number is to calculate your Basal Metabolic Rate (BMR) using a validated formula, then multiply it by a factor that reflects how active you are. The whole process takes about two minutes with a calculator.
Step 1: Calculate Your Basal Metabolic Rate
Your BMR is the energy your body uses just to stay alive: breathing, circulating blood, maintaining body temperature, and keeping your organs running. It typically accounts for the largest share of your daily calorie burn. The Mifflin-St Jeor equation is the formula most commonly recommended for this step. You’ll need your weight in kilograms, your height in centimeters, and your age in years.
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
If you’re working in pounds and inches, convert first. Divide your weight in pounds by 2.2 to get kilograms, and multiply your height in inches by 2.54 to get centimeters. As a quick example, a 35-year-old woman who weighs 150 pounds (68 kg) and stands 5’6″ (167.6 cm) would calculate: (10 × 68) + (6.25 × 167.6) − (5 × 35) − 161, which comes out to about 1,392 calories per day as her BMR.
Step 2: Multiply by Your Activity Level
Your BMR only covers what your body burns at complete rest. To get your actual maintenance calories, you multiply it by an activity factor that accounts for movement throughout the day, exercise, and even the energy your body uses digesting food.
- Sedentary (little or no exercise): BMR × 1.2
- Lightly active (exercise 1–2 days per week): BMR × 1.375
- Moderately active (exercise 3–5 days per week): BMR × 1.55
- Very active (intense training or active sports): BMR × 1.725
- Extra active (physically demanding job): BMR × 1.9
Continuing the example above: if that 35-year-old woman exercises three days a week, she’d multiply 1,392 by 1.55, giving her an estimated maintenance level of roughly 2,158 calories per day. That’s her starting number.
Most people overestimate their activity level. If you work a desk job and exercise a few times per week, “lightly active” or “moderately active” is probably where you fall. Choosing “very active” when it doesn’t truly fit can inflate your estimate by several hundred calories.
Why Your Number Is an Estimate, Not a Fact
No formula is perfectly accurate. A study comparing several popular equations found that the Mifflin-St Jeor and Harris-Benedict formulas each predicted resting metabolic rate within 10% of the measured value for only about 56–58% of participants. That means for roughly four out of ten people, the formula is off by more than 10% in either direction. This isn’t a flaw you can fix by picking a better equation. It’s a limitation of using a formula instead of lab equipment.
Fitness trackers don’t solve this problem. Research from Harvard’s School of Engineering found that calorie-burn estimates from wearable devices carry error rates of 30–80%. The step counts are useful, but treat the calorie number on your wrist as a rough guide rather than a precise measurement.
The Hidden Variable: Daily Movement Outside Exercise
One reason formulas miss the mark for many people is a component called non-exercise activity thermogenesis, or NEAT. This is every calorie you burn through movement that isn’t structured exercise: walking to the kitchen, fidgeting, standing while cooking, carrying groceries, even gesturing while talking. The difference in NEAT between two people of similar size can be as large as 2,000 calories per day, mostly driven by occupation and lifestyle habits.
A warehouse worker and an accountant who are the same height, weight, and age could have wildly different maintenance calories, even if both go to the gym three times a week. The activity multipliers try to capture this, but they compress enormous variation into five broad categories. If your day involves a lot of walking, cleaning, or being on your feet, you may burn significantly more than a calculator suggests.
A Better Formula if You Know Your Body Fat
The Mifflin-St Jeor equation uses total body weight, which means it treats a pound of muscle the same as a pound of fat. If you carry more muscle than average for your height and weight, it will likely underestimate your BMR. If you carry more fat, it may overestimate it.
The Katch-McArdle formula addresses this by using lean body mass instead of total weight:
BMR = 370 + (21.6 × lean body mass in kg)
To use it, you need a reasonable estimate of your body fat percentage. If you know you’re at 25% body fat and weigh 80 kg, your lean mass is 60 kg, giving a BMR of 370 + (21.6 × 60) = 1,666 calories. You’d then apply the same activity multipliers from Step 2. This formula is particularly useful for people who are notably muscular or notably high in body fat, since lean tissue is far more metabolically active than fat tissue.
What About the Calories You Burn Digesting Food?
Your body spends energy breaking down and absorbing the food you eat. This is called the thermic effect of food, and it accounts for roughly 10% of your total daily burn. Not all nutrients cost the same amount of energy to process. Protein increases your metabolic rate by 15–30% of the calories consumed, carbohydrates by 5–10%, and fats by just 0–3%. This is one reason high-protein diets can have a slight metabolic advantage.
The activity multipliers already factor in a general thermic effect, so you don’t need to add it separately. But it’s worth understanding because it explains why two diets with the same calorie count can produce slightly different results depending on their protein content.
How to Refine Your Number With Real Data
The best approach is to treat your calculated TDEE as a starting point and then adjust based on what actually happens. Eat at your estimated maintenance calories for two to three weeks while weighing yourself at the same time each morning. Track the weekly average rather than daily fluctuations, since water weight can swing by a pound or more from day to day.
If your average weight stays stable over two to three weeks, you’ve found your maintenance calories. If you’re slowly gaining, reduce by 100–200 calories and reassess. If you’re slowly losing, add 100–200 calories. This feedback loop is far more accurate than any formula because it accounts for your specific metabolism, your actual activity, and every variable that equations can’t capture.
Keep in mind that maintenance calories aren’t fixed. They shift as you age, gain or lose weight, change your activity habits, or alter your body composition. After significant weight loss, your body may temporarily burn slightly fewer calories than predicted. Research published in The American Journal of Clinical Nutrition measured this dip at roughly 50 calories per day on average after weight loss, though it tended to fade within one to two years. It’s a real effect, but a small one.