Your maintenance calories are the number of calories you burn in a full day, accounting for everything from breathing to walking to digesting food. Most adults fall somewhere between 1,800 and 3,000 calories per day, but the exact number depends on your size, body composition, age, and how much you move. There are several ways to estimate yours, each with different levels of accuracy.
What Makes Up Your Daily Burn
Your total daily energy expenditure has four components. The largest, by far, is your basal metabolic rate (BMR): the energy your body uses just to stay alive while completely at rest. This covers heartbeat, breathing, brain function, cell repair, and temperature regulation. For most people, BMR accounts for roughly 60 to 70 percent of all calories burned in a day.
The second component is non-exercise activity, which includes every movement that isn’t intentional exercise: fidgeting, walking to the kitchen, standing at your desk, carrying groceries. This varies enormously between people and can represent anywhere from 15 to 30 percent of total burn. Someone with an active job and a restless temperament may burn several hundred more calories through these unconscious movements than someone who sits most of the day.
Exercise itself is typically the smallest variable component for most people, often just 5 to 10 percent of daily burn unless you train heavily. The final piece is the thermic effect of food, the energy your body spends digesting and absorbing what you eat, which accounts for roughly 10 percent of your intake. Protein costs the most energy to digest, followed by carbohydrates, then fat.
Estimate With a Formula
The most widely recommended equation for estimating BMR is the Mifflin-St Jeor formula. In validation studies comparing its predictions against lab measurements of actual metabolic rate, it landed within 10 percent of the true value for about 82 to 87 percent of non-obese adults. It also showed no systematic bias, meaning it didn’t consistently over- or underestimate. Most other popular equations tend to overestimate, which makes them less useful if you’re trying to find a genuine maintenance number.
The Mifflin-St Jeor formula 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 your BMR in calories per day. To convert that to total daily burn, you multiply by an activity factor. The Food and Agriculture Organization of the United Nations classifies these into three broad tiers:
- Sedentary or lightly active (desk job, minimal exercise): multiply by 1.4 to 1.69
- Moderately active (regular exercise or active job): multiply by 1.7 to 1.99
- Vigorously active (heavy daily training or physical labor): multiply by 2.0 to 2.4
Most people overestimate their activity level. If you work at a computer and exercise three or four times a week, you’re probably in the upper end of the sedentary range or the lower end of moderately active, somewhere around 1.5 to 1.7. Values above 2.4 are considered difficult to sustain over time, even for athletes.
Why Body Composition Matters
Two people who weigh the same can have very different maintenance calories. The reason is muscle. Skeletal muscle burns roughly 4.5 to 7 calories per pound per day at rest, while fat tissue is far less metabolically active. Someone carrying more muscle mass at the same body weight will have a higher BMR, and formulas that only use height, weight, age, and sex can’t fully capture that difference.
This is one of the formula’s blind spots. If you’ve been strength training for years, a standard equation may underestimate your needs. If you carry a higher percentage of body fat at a given weight, it may overestimate. The accuracy rate of the Mifflin-St Jeor equation drops to about 70 to 75 percent for people with obesity, partly for this reason.
The Bodyweight Tracking Method
Formulas give you a starting point. 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, then do some simple math.
Weigh yourself each morning, after using the bathroom and before eating. Record everything you eat as accurately as you can, using a food scale for portions and a calorie-tracking app to log meals. After 14 to 21 days, compare your average daily intake to your weight trend. If your weight stayed essentially flat (within about a pound in either direction), your average daily intake during that period is a solid estimate of your maintenance calories.
If your weight went up, your average intake was above maintenance. If it dropped, you were below. Since roughly 3,500 calories corresponds to about one pound of body weight change, you can estimate the gap. For example, if you ate an average of 2,400 calories per day and lost one pound over two weeks, your maintenance is probably around 2,650 calories (2,400 plus the 250-per-day deficit that produced that pound of loss).
This method accounts for your actual muscle mass, your actual activity, and your individual metabolism in a way no equation can. The tradeoff is that it requires honest, consistent tracking.
Why Wearables Aren’t Reliable Enough
Fitness trackers and smartwatches display a “calories burned” number that feels precise, but estimated error rates for commercial wearables range from 30 to 80 percent. That means a watch reporting 2,500 calories burned could be off by 750 to 2,000 calories in either direction. The sensors do a reasonable job tracking heart rate and step count, but converting that data into an accurate calorie estimate involves assumptions about your body that the device can’t verify.
If you use a wearable, treat its calorie estimate as a rough directional signal rather than a number you can build a diet around. It’s more useful for comparing one day to another (did I move more today than yesterday?) than for pinpointing your maintenance level.
Your Maintenance Calories Can Shift Over Time
Maintenance isn’t a fixed number. It changes as your weight, muscle mass, activity, and age change. One particularly important shift happens after significant weight loss. Your body adapts by burning fewer calories than a formula would predict for your new weight, a phenomenon called adaptive thermogenesis. In most studies, this metabolic slowdown amounts to roughly 30 to 100 calories per day beyond what the weight loss alone would explain. After extreme weight loss of 50 pounds or more, the gap can be larger, sometimes 200 to 500 calories per day, and it can persist for months or even years.
This is one reason people who’ve lost a lot of weight often find that eating what “should” be maintenance for their new size still leads to gradual regain. If you’ve recently lost weight, it’s worth recalculating and using the bodyweight tracking method to find your true new baseline rather than relying on a formula alone.
A Practical Starting Plan
Run the Mifflin-St Jeor formula with an honest activity multiplier. This gives you a reasonable first estimate. Eat at that level for two weeks while weighing yourself daily and averaging the numbers at the end of each week. If your weekly average weight is stable, you’ve found your maintenance. If it’s trending up or down, adjust by 100 to 200 calories and repeat for another two weeks.
Most people land on their true maintenance number within four to six weeks of this process. Once you have it, you only need to recheck every few months or after major changes in your routine, body weight, or training volume. The number will drift over time, but it won’t change dramatically week to week. Patience with the process is what separates a guess from a number you can actually use.