Your maintenance calories are the number of calories you burn in a full day, accounting for everything from breathing to exercise. Eat this amount consistently and your weight stays stable. The most practical way to find yours is to combine a formula-based estimate with real-world tracking over two to four weeks.
Start With a Formula
Several equations estimate your resting metabolic rate (RMR), the calories your body burns just to keep you alive. A systematic review in the Journal of the American Dietetic Association compared the most commonly used formulas and found that the Mifflin-St Jeor equation was the most reliable, predicting resting metabolic rate within 10% of the measured value in more people than any other equation tested. It also had the narrowest error range across both normal-weight and obese individuals.
The Mifflin-St Jeor equation works like this:
- Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
- Women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
This gives you a resting number. You then multiply it by an activity factor to get your total daily energy expenditure, which is your estimated maintenance calories. The Food and Agriculture Organization of the United Nations classifies activity levels into three broad tiers:
- Sedentary or lightly active (desk job, occasional walks): multiply by 1.4 to 1.69
- Moderately active (regular exercise, active job): multiply by 1.7 to 1.99
- Vigorously active (hard daily training, physical labor): multiply by 2.0 to 2.4
Activity levels above 2.4 are difficult to sustain over long periods. Most people with desk jobs who exercise a few times a week fall somewhere in the 1.5 to 1.7 range. If you’re unsure, start at the lower end. It’s easier to adjust upward than to overcorrect.
If You Know Your Body Fat Percentage
Standard formulas use your total body weight, but two people at the same weight can have very different metabolic rates depending on how much of that weight is muscle versus fat. Muscle tissue burns roughly 4.5 to 7 calories per pound per day at rest, which adds up when you carry significantly more or less of it than average.
The Katch-McArdle formula accounts for this by using lean body mass instead of total weight. First, calculate your lean mass: subtract your fat mass from your total weight. For example, if you weigh 80 kg at 20% body fat, your lean body mass is 80 – (80 × 0.20) = 64 kg. Then plug that into the formula: 370 + (21.6 × lean body mass in kg). For that example, the resting metabolic rate comes out to about 1,752 calories. You’d still multiply by an activity factor to get your maintenance estimate.
This formula is most useful if you’ve had your body fat percentage measured through a DEXA scan or similar method. Eyeballing body fat with an online chart introduces enough guesswork that you may not gain much accuracy over Mifflin-St Jeor.
Why Formulas Are Only a Starting Point
Every formula is a population-level estimate applied to an individual body. The Mifflin-St Jeor equation, even as the best available option, still has noteworthy errors when applied to specific people, and its accuracy can vary by age and ethnicity. Your genetics, hormonal profile, sleep quality, and daily non-exercise movement (fidgeting, pacing, how much you stand) all shift your actual burn in ways no equation captures.
Wearable fitness trackers aren’t much better for pinning down exact numbers. Research from Harvard’s School of Engineering found that calorie-burn estimates from smartwatches carry error rates of 30 to 80%. That “450 calories burned” notification after a run could mean you actually burned anywhere from 250 to 600. Wearables are more useful for spotting trends over weeks than for trusting any single day’s readout.
Use Real-World Data to Dial It In
The most reliable way to find your true maintenance calories is to pair a formula estimate with consistent tracking. Pick a calorie target based on your calculation, eat at that level for two to three weeks, and monitor your weight. Weigh yourself at the same time each day (morning, after using the bathroom) and look at the weekly average rather than any single reading. Daily fluctuations of one to three pounds from water, sodium, and digestion are normal and meaningless.
If your weekly average weight holds steady over two to three weeks, you’ve found your maintenance range. If it trends downward, you’re eating below maintenance and can add 100 to 200 calories. If it trends upward, subtract the same amount. Small adjustments and patience are the whole method. Trying to nail the number in a few days leads to overcorrecting based on water weight swings.
Tracking food accurately matters here. Use a kitchen scale rather than eyeballing portions. Cooking oils, sauces, nuts, and liquid calories are the most commonly underestimated items. Most people underreport calorie intake by 20 to 30% when relying on rough estimates, which makes the tracking period useless if you aren’t measuring.
Signs Your Intake Is Too Low
If you’ve been eating at a level you think is maintenance but you’re experiencing persistent fatigue, increased hunger and cravings, hair thinning, feeling cold when others don’t, constipation, frequent illness, or low mood, your body is likely getting fewer calories than it needs. These are physiological stress signals, not character flaws. Hormonal changes from undereating drive many of these symptoms, particularly the spikes in appetite hormones that make cravings feel uncontrollable.
For a rough floor, the Dietary Guidelines for Americans suggest that adult women need at least 1,600 calories per day and adult men need at least 2,200 just for basic weight maintenance. Most active people need considerably more. If your calculated maintenance number falls below these thresholds, it’s worth questioning whether the inputs (weight, height, activity level) are accurate.
How Weight Loss History Affects Your Number
If you’ve recently lost a significant amount of weight, your maintenance calories may be temporarily lower than formulas predict. This phenomenon, sometimes called metabolic adaptation, means your body burns fewer calories than expected for your new size. In one example from metabolic chamber research, a person who lost 22 pounds and would be expected to need about 2,200 calories actually needed only 2,000. That 200-calorie gap can make weight regain feel almost automatic if you eat what the math says you “should” need.
The encouraging finding is that this adaptation shrinks over time. When researchers gave participants a month after weight loss for their bodies to stabilize, the adaptation dropped sharply, averaging only a few dozen calories per day below pre-weight-loss levels. If you’ve recently finished a diet, your maintenance calories will likely creep upward over the following weeks as your metabolism recalibrates. This is a good reason to increase calories gradually after a weight-loss phase rather than jumping straight to your calculated maintenance.
Your Number Will Change
Maintenance calories aren’t a fixed value you calculate once and follow forever. They shift with your age, weight, muscle mass, activity patterns, stress levels, and even the seasons. Someone who picks up strength training will gradually raise their resting metabolic rate. Someone who switches from an active job to a desk role will lower theirs. Recalculating every few months, or whenever your routine changes significantly, keeps the number useful. The formula gives you a starting point. Your body gives you the answer.