Most adults need between 1,600 and 3,000 calories per day to maintain their weight, depending on sex, age, height, weight, and how much they move. That range is wide because no single number works for everyone. Your maintenance calories are the amount you’d need to eat each day to neither gain nor lose weight, and figuring out your personal number takes just a few steps.
Quick Reference by Age and Activity Level
The U.S. Dietary Guidelines provide estimated maintenance calories based on a reference man (5’10”, 154 lbs) and reference woman (5’4″, 126 lbs). These are useful starting points even if your body doesn’t match those references exactly.
For adult males:
- Sedentary: 2,000 to 2,600 calories, depending on age
- Moderately active: 2,200 to 2,800 calories
- Active: 2,400 to 3,000 calories
For adult females:
- Sedentary: 1,600 to 2,000 calories
- Moderately active: 1,800 to 2,200 calories
- Active: 2,000 to 2,400 calories
“Sedentary” means you’re only doing the movement required for daily living. “Moderately active” is roughly equivalent to walking 1.5 to 3 miles per day on top of that. “Active” means walking more than 3 miles per day or doing equivalent exercise. The numbers trend downward as you age, dropping by roughly 200 calories between your twenties and your sixties for sedentary individuals.
How to Calculate Your Personal Number
The most widely recommended formula for estimating maintenance calories is the Mifflin-St Jeor equation. It calculates your resting metabolic rate (the calories your body burns just to stay alive), and then you multiply that by an activity factor.
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
To convert your weight to kilograms, divide pounds by 2.2. To convert height to centimeters, multiply inches by 2.54. So a 35-year-old woman who is 5’6″ (167.6 cm) and weighs 150 lbs (68.2 kg) would calculate: (10 × 68.2) + (6.25 × 167.6) − (5 × 35) − 161 = 1,394 calories at rest.
That resting number then gets multiplied by an activity factor from the Food and Agriculture Organization’s physical activity scale:
- Sedentary or lightly active: multiply by 1.4 to 1.69
- Moderately active: multiply by 1.7 to 1.99
- Vigorously active: multiply by 2.0 to 2.4
Using the example above, that 35-year-old woman with a moderately active lifestyle would multiply 1,394 by about 1.7, landing around 2,370 calories per day to maintain her weight. Someone sedentary with the same stats would need closer to 1,950.
Where Your Calories Actually Go
Your body spends energy on three main things, and understanding the breakdown helps explain why two people of similar size can have very different maintenance needs.
Resting metabolism accounts for the largest share, typically 60 to 70% of total daily burn. This is what your organs, brain, and tissues need just to keep functioning. Your brain alone is a significant energy consumer, and internal organs burn 15 to 40 times more calories per unit of weight than muscle does, and 50 to 100 times more than fat tissue.
Physical activity makes up the most variable portion. This includes both structured exercise and all the smaller movements throughout your day: fidgeting, standing, walking to the kitchen, taking the stairs. This non-exercise movement can vary by up to 2,000 calories per day between two people of similar size, according to research from the Mayo Clinic. That’s an enormous range, and it explains why someone with a physically demanding job or a restless temperament may maintain their weight on significantly more food than someone who sits most of the day.
Digesting food itself burns about 10% of your caloric intake. Your body uses energy to break down, absorb, and process the food you eat. Protein requires the most energy to digest, while fat requires the least.
Why Muscle Mass Matters
Muscle burns roughly 4.5 to 7 calories per pound per day at rest. Fat tissue burns considerably less. This means two people who weigh the same but carry different amounts of muscle will have different maintenance calorie needs. The difference per pound isn’t dramatic on its own, but across 10 or 20 pounds of additional muscle, it adds up to a meaningful daily gap.
This is one reason the formulas above are estimates. They use total body weight rather than distinguishing between muscle and fat, so they can overestimate needs for someone with a high body fat percentage and underestimate for someone who is muscular.
Does Metabolism Slow With Age?
Less than you probably think. A large-scale study highlighted by Harvard Health found that both total and resting energy expenditure remain stable from ages 20 to 60, regardless of sex. The gradual calorie reductions in the USDA tables are real, but they largely reflect changes in body composition (losing muscle, gaining fat) and reduced physical activity rather than an unavoidable metabolic slowdown.
After 60, metabolism does begin to decline more noticeably. But through middle age, weight gain is more about moving less and eating more than it is about a body that suddenly burns fewer calories.
Maintenance After Weight Loss
If you’ve recently lost weight, your maintenance calories will be somewhat lower than the formulas predict. Your body adapts to the calorie deficit by becoming slightly more efficient, a phenomenon called adaptive thermogenesis. A systematic review of 33 studies found this effect in the vast majority of cases, with the typical reduction ranging from about 30 to 100 extra calories per day beyond what would be expected from the smaller body size alone.
For people who lost extreme amounts of weight (over 100 lbs), the effect was larger, sometimes several hundred calories per day. However, the same review found that this metabolic adaptation tends to fade after a period of weight stabilization. In other words, if you maintain your new weight for a while, your metabolism generally adjusts upward toward the predicted level. During that transition period, though, expect your true maintenance number to sit slightly below what a calculator tells you.
Finding Your Real Number
Formulas give you a starting estimate. Your actual maintenance calories are best confirmed through tracking. Pick a calorie target based on your calculation, eat that amount consistently for two to three weeks, and monitor your weight. Weigh yourself at the same time each day (morning, before eating) and use the weekly average rather than any single reading, since daily weight can fluctuate by several pounds due to water, salt, and digestion.
If your average weight stays stable over two to three weeks, you’ve found your maintenance range. If you’re slowly gaining, reduce by 100 to 200 calories. If you’re slowly losing, add the same. This real-world calibration is more accurate than any equation because it accounts for your specific metabolism, activity patterns, and body composition all at once.
Keep in mind that your maintenance calories aren’t fixed. They shift as your weight changes, as your activity level changes seasonally, and as you age. Recalculating every few months or whenever your routine shifts significantly keeps the number useful.