Your maintenance calories are the number of calories you burn in a full day, including everything from breathing to walking to exercising. For most adults, this falls somewhere between 1,800 and 3,000 calories per day, depending on your size, age, sex, and how active you are. You can estimate this number with a simple two-step process: calculate your resting metabolic rate, then multiply it by an activity factor.
Step 1: Calculate Your Resting Metabolic Rate
Your resting metabolic rate (RMR) is the energy your body uses just to stay alive: pumping blood, breathing, maintaining body temperature, keeping your brain running. For most people, this accounts for 60 to 70 percent of total daily calorie burn. The most widely recommended formula for estimating it is the Mifflin-St Jeor equation, which the Academy of Nutrition and Dietetics considers the most accurate option for the general population.
Here’s how it works. You’ll need your weight in kilograms (divide pounds by 2.2) and your height in centimeters (multiply inches by 2.54):
- Men: (9.99 × weight in kg) + (6.25 × height in cm) − (4.92 × age) + 5
- Women: (9.99 × weight in kg) + (6.25 × height in cm) − (4.92 × age) − 161
So a 35-year-old woman who weighs 150 pounds (68 kg) and stands 5’6″ (168 cm) would calculate: (9.99 × 68) + (6.25 × 168) − (4.92 × 35) − 161 = roughly 1,400 calories at rest. A 35-year-old man with the same height and weight would get about 1,565. The difference comes from the equation’s adjustment for sex, which reflects average differences in muscle mass and hormonal metabolism.
Notice that age works against you. The formula subtracts about 5 calories per day for every year of age, which lines up with the gradual decline in metabolic rate most people experience over time.
Step 2: Multiply by Your Activity Level
Your RMR only covers what your body burns at rest. To get your total daily energy expenditure (your actual maintenance calories), multiply your RMR by an activity factor:
- Sedentary (desk job, no regular exercise): RMR × 1.4
- Lightly active (light exercise 1 to 3 days per week): RMR × 1.375
- Moderately active (exercise 3 to 5 days per week): RMR × 1.55
- Very active (hard exercise 6 to 7 days per week): RMR × 1.725
- Extremely active (physical job plus intense training): RMR × 1.9
Using the example above, that 35-year-old woman with an RMR of 1,400 who exercises moderately would multiply 1,400 × 1.55, giving her an estimated maintenance of about 2,170 calories per day.
This is where most of the error creeps in. People consistently overestimate their activity level. If you work out three times a week but spend the other 12 waking hours sitting, “lightly active” is probably more honest than “moderately active.” The multipliers range all the way from 1.4 to 2.4 across populations, and picking the wrong one can throw your estimate off by several hundred calories. When in doubt, start with a lower multiplier.
If You Know Your Body Fat Percentage
The Mifflin-St Jeor formula uses total body weight, which means it treats a 200-pound person with 15% body fat the same as a 200-pound person with 35% body fat. That’s a problem, because muscle tissue burns significantly more energy at rest than fat tissue does. If you’re particularly muscular or you know your body fat percentage from a DEXA scan or reliable calipers, the Katch-McArdle formula gives a better estimate.
First, calculate your lean body mass: your total weight minus your fat weight. If you weigh 200 pounds and carry 20% body fat, your lean mass is 160 pounds (72.7 kg). Then plug it in:
- RMR = 370 + (21.6 × lean body mass in kg)
For that 200-pound person with 72.7 kg of lean mass: 370 + (21.6 × 72.7) = about 1,940 calories at rest. You’d then apply the same activity multipliers from step 2. This formula doesn’t differentiate between men and women because it accounts for body composition directly, which is the main driver of the metabolic difference between sexes in the first place.
Why Your Estimate Is Just a Starting Point
Every formula is an approximation. Individual metabolic rates can vary by 10 to 15 percent from what any equation predicts, due to genetics, hormonal differences, gut bacteria, and other factors no formula captures. That’s why the most reliable way to find your true maintenance calories is to use the formula as a starting point, then track what actually happens to your weight.
Eat at your calculated maintenance for two to three weeks while weighing yourself at the same time each day (morning, after using the bathroom). If your average weight stays stable over that stretch, you’ve found your number. If you’re slowly gaining, drop 100 to 200 calories. If you’re slowly losing, add the same amount. Daily weight fluctuates due to water retention, sodium intake, and digestion, so focus on the weekly trend rather than any single day’s reading.
What Your Diet Composition Changes
Not all calories cost the same amount of energy to digest. Your body burns calories just breaking down and absorbing food, a process called the thermic effect of food. Protein is the most metabolically expensive: digesting it burns 15 to 30 percent of the calories it contains. Carbohydrates cost 5 to 10 percent, and fats cost 0 to 3 percent.
In practical terms, this means two people eating the same total calories can have slightly different effective maintenance levels based on how much protein they eat. Someone eating 2,200 calories with 30% of those calories from protein will burn more energy through digestion alone than someone eating 2,200 calories with only 10% from protein. The difference might be 50 to 100 calories per day, which is modest but adds up over weeks. This is one reason high-protein diets tend to make weight maintenance easier.
How Weight Loss Changes the Number
If you’ve recently lost a significant amount of weight, your maintenance calories will be lower than what the formulas predict for your new weight. This is sometimes called metabolic adaptation. A person who drops from 220 pounds to 198 pounds might expect their energy needs to fall from 2,500 to around 2,200 calories based on their new weight alone. But measurements in metabolic chambers often show the actual number is closer to 2,000, a bigger drop than body size alone would explain.
The reassuring part: this effect appears to be mostly temporary. Research tracking people after weight loss shows that when the body is given about a month to stabilize at the new weight, metabolic adaptation shrinks to only a few dozen calories per day below what you’d predict. Your metabolism isn’t permanently “damaged” by dieting, but it does need time to recalibrate. If you’ve recently lost weight, start with a slightly lower maintenance estimate and adjust upward gradually as your body settles in.
Putting It All Together
The fastest path to your maintenance calories is straightforward: run the Mifflin-St Jeor calculation, multiply by an honest activity factor, and eat at that level for two to three weeks while monitoring your weight trend. Adjust in small increments based on what the scale actually does. If you know your body fat percentage, the Katch-McArdle formula will give you a more personalized starting point. Either way, treat the number as a living estimate that shifts with your activity, age, diet, and weight history, not a fixed target carved in stone.