Your maintenance calories are the number of calories you burn in a full day, accounting for everything from breathing to exercise. Most adults fall somewhere between 1,800 and 3,000 calories per day, but the exact number depends on your size, age, sex, and how much you move. There are two reliable ways to find yours: calculate an estimate using a formula, then refine it with real-world tracking.
What Makes Up Your Daily Calorie Burn
Your total daily energy expenditure (TDEE) breaks down into three main categories, and understanding them helps explain why two people of the same weight can have very different maintenance numbers.
Resting metabolic rate (RMR) is the energy your body uses just to stay alive: pumping blood, breathing, maintaining body temperature, running your brain. This accounts for roughly 60 to 70% of all the calories you burn in a day. It’s the biggest piece by far, which is why your body size and composition matter so much.
Physical activity covers everything from structured exercise to walking around your kitchen. This is the most variable component and the one you have the most control over. For sedentary people it might represent 15 to 20% of daily burn; for very active people it can rival resting metabolism.
The thermic effect of food is the energy your body spends digesting, absorbing, and processing what you eat. It accounts for about 10% of your daily total. Protein costs the most to process, raising your metabolic rate by 15 to 30% of the calories in that protein. Carbohydrates cost 5 to 10%, and fats cost just 0 to 3%. This is one reason high-protein diets have a slight metabolic edge.
Step 1: Estimate Your Resting Metabolic Rate
The Mifflin-St Jeor equation is the most widely recommended starting formula. The Academy of Nutrition and Dietetics considers it the most accurate option for most people. It predicted resting metabolic rate within 10% of the true measured value in 70% of individuals studied, outperforming the older Harris-Benedict equation, which hit that same accuracy range in only 39 to 64% of people.
The formula uses your weight in kilograms, height in centimeters, and age in years:
- Men: (9.99 × weight) + (6.25 × height) − (4.92 × age) + 5
- Women: (9.99 × weight) + (6.25 × height) − (4.92 × age) − 161
To convert: divide your weight in pounds by 2.2 to get kilograms, and multiply your height in inches by 2.54 to get centimeters. So a 170-pound, 5’10” man who is 30 years old would calculate: (9.99 × 77.3) + (6.25 × 177.8) − (4.92 × 30) + 5, which comes out to about 1,737 calories per day at rest.
If you know your body fat percentage (from a DEXA scan, for example), the Katch-McArdle formula may be more accurate, especially if you carry significantly more muscle than average. It uses lean body mass directly: 370 + (21.6 × lean body mass in kg). You calculate lean body mass by subtracting your fat mass from your total weight. A 200-pound person at 15% body fat has 170 pounds of lean mass (about 77.1 kg), giving an estimated resting burn of around 2,035 calories.
Step 2: Multiply by Your Activity Level
Your resting metabolic rate only reflects what your body burns doing nothing. To estimate total daily burn, multiply it by a physical activity factor. The Academy of Nutrition and Dietetics uses these ranges:
- Sedentary (desk job, little exercise): 1.0 to 1.4
- Low active (light exercise 1 to 3 days per week): 1.4 to 1.6
- Active (moderate exercise 3 to 5 days per week): 1.6 to 1.9
- Very active (hard daily exercise or physical job): 1.9 to 2.5
Most people overestimate their activity level. If you work at a desk and hit the gym three times a week for 45 minutes, you’re solidly in the low-active range, not the active one. Using the example above, that 30-year-old man with an RMR of 1,737 would multiply by about 1.5, landing at roughly 2,600 calories per day as a starting estimate.
Step 3: Refine With Real-World Tracking
Every formula gives you a starting point, not a verdict. The only way to find your true maintenance calories is to test the estimate against what actually happens to your body. Here’s how to do it over two to three weeks:
Track your food intake as accurately as you can. Use a kitchen scale for portions and a calorie-tracking app to log everything, including cooking oils, sauces, and drinks. Eyeballing portions typically leads to underestimating by 20 to 50%, which defeats the purpose.
Weigh yourself daily at the same time (first thing in the morning, after using the bathroom) and average each week. Daily weight fluctuates by one to four pounds due to water, sodium, and digestion, so individual weigh-ins are meaningless. The weekly average is what matters.
If your weekly average stays roughly the same over two to three weeks while eating a consistent number of calories, you’ve found your maintenance range. If you’re losing about half a pound per week, you’re eating roughly 250 calories below maintenance. If you’re gaining, you’re above it. Adjust by 100 to 200 calories and repeat until your weight stabilizes.
Why Online Calculators and Wearables Miss
Online TDEE calculators all use the same handful of formulas, so they’re only as good as the formula itself and the activity multiplier you choose. Even the best formula (Mifflin-St Jeor) misses by more than 10% for about 30% of people. That could mean a 200- to 300-calorie gap between your calculated number and your real burn.
Fitness trackers are even less reliable for calorie estimates. Research from Harvard’s School of Engineering found that smartwatch calorie-burn readings carry estimated error rates of 30 to 80%. That means if your watch says you burned 500 calories on a run, the real number could be anywhere from 100 to 650. Wearables are useful for tracking trends in activity and heart rate, but don’t set your calorie targets based on what they report.
Age, Weight Loss, and Shifting Targets
Your maintenance calories aren’t fixed. They shift as your body changes, and two factors catch people off guard.
A large study of over 6,600 people across 29 countries, led by researcher Herman Pontzer, found that metabolism doesn’t decline in your 20s or 30s the way most people assume. Pound for pound, metabolic rate stays remarkably stable from about age 20 through 60. The meaningful decline starts after 60. So if your maintenance calories dropped between 25 and 40, it’s almost certainly because you lost muscle mass or became less active, not because aging slowed your metabolism.
After significant weight loss, your body temporarily burns fewer calories than you’d expect for your new size. In one example, a person who dropped from 220 to 198 pounds would be expected to need about 2,200 calories, but metabolic chamber measurements showed they needed only 2,000. This gap, sometimes called metabolic adaptation, sounds alarming but appears to be short-lived. When researchers gave participants about a month at their new weight, the adaptation shrank to just a few dozen calories per day. The practical takeaway: after losing weight, recalculate using your new weight. You may need to eat slightly less than the formula predicts for a few weeks, but your metabolism largely catches up.
Practical Tips for Accuracy
Pick one formula and one tracking method, then stick with them for consistency. Switching between apps or calculation methods introduces noise that makes it harder to spot real trends. The Mifflin-St Jeor equation paired with a food scale and daily weigh-ins is the most reliable low-cost approach available.
Be honest about your activity level when choosing a multiplier. If in doubt, round down. It’s easier to add 100 to 200 calories after a week of unexpected weight loss than to undo a week of accidental overeating. Also keep in mind that your non-exercise movement matters more than most people realize. Fidgeting, standing, walking to the car, doing laundry: this background activity varies enormously between individuals and can account for several hundred calories per day. If you switch from an active job to a desk job, your maintenance number can drop by 300 to 500 calories even if your gym routine stays the same.
Recalculate every time your weight changes by more than 10 pounds, your activity level shifts significantly, or you haven’t checked in three to six months. Maintenance isn’t a number you find once. It’s a range you revisit as your life changes.