The number of calories you need to maintain your weight depends on your age, sex, height, weight, and how active you are, but most adults fall somewhere between 1,600 and 3,200 calories per day. Your exact number is called your Total Daily Energy Expenditure, or TDEE, and you can estimate it with a simple formula or dial it in over time by tracking your weight and intake.
What Makes Up Your Daily Calorie Burn
Your body burns calories in three main ways. The largest share, about 60 to 70 percent of your total, goes to basic life-sustaining functions: breathing, circulating blood, maintaining body temperature, and keeping your organs running. This is your resting energy expenditure, the calories you’d burn lying in bed all day doing nothing.
Physical activity accounts for 15 to 50 percent of your daily burn, depending on how much you move. For someone with a desk job who doesn’t exercise, it’s closer to 15 percent. For a construction worker or serious athlete, it can reach half of all calories burned. The remaining roughly 10 percent goes toward digesting and absorbing the food you eat. Your body spends real energy breaking down meals, which is why eating itself costs calories.
How to Estimate Your Number
The most widely recommended formula for estimating resting calories is the Mifflin-St Jeor equation. You’ll need your weight in kilograms (divide pounds by 2.2), your height in centimeters (multiply inches by 2.54), and your age in years.
- For men: (9.99 × weight) + (6.25 × height) − (4.92 × age) + 5
- For women: (9.99 × weight) + (6.25 × height) − (4.92 × age) − 161
This gives you a resting number. To get your maintenance calories, multiply the result by an activity factor: 1.2 for a sedentary lifestyle, 1.4 to 1.59 for light activity like walking a few times a week, 1.6 to 1.89 for regular exercise, and 1.9 or above for intense daily training or a physically demanding job.
As an example, a 35-year-old woman who weighs 150 pounds (68 kg) and stands 5’5″ (165 cm) would get a resting estimate of about 1,387 calories. With light activity (multiplied by 1.4), her maintenance level would land around 1,940 calories per day. A 35-year-old man at 180 pounds (82 kg) and 5’10” (178 cm) would get a resting estimate of roughly 1,770, putting his lightly active maintenance around 2,480 calories.
These are starting points, not exact answers. The formula can’t account for your individual muscle mass, genetics, or hormonal profile. The best approach is to use the estimate for two to three weeks, weigh yourself under consistent conditions (same time of day, same clothing), and adjust up or down by 100 to 200 calories based on what the scale does.
Why Muscle Mass Matters
Muscle tissue burns roughly 4.5 to 7 calories per pound per day at rest. That might not sound like much, but it adds up. Someone carrying 20 extra pounds of muscle compared to another person of the same weight burns an additional 90 to 140 calories daily just by existing. This is one reason two people of the same height, weight, and age can have noticeably different maintenance calorie needs. It’s also why strength training can gradually raise your baseline calorie burn over time, making weight maintenance easier.
How Age Changes the Equation
Metabolism doesn’t crash overnight, but it does decline steadily. A large study published in Science found that adjusted metabolic rate drops by about 0.7 percent per year through adulthood. By age 90, total energy expenditure is roughly 26 percent lower than in middle-aged adults. In practical terms, this means a 55-year-old needs fewer calories than they did at 35, even if their activity level and body composition haven’t changed much. For each decade after your 20s, expect to need somewhere around 50 to 100 fewer daily calories to stay at the same weight, assuming everything else holds steady.
The Calorie Penalty After Weight Loss
If you’ve lost a significant amount of weight, your maintenance calories will be lower than a formula predicts. This is one of the most important and least understood aspects of weight maintenance. After losing 10 percent or more of your body weight, your daily calorie burn drops by 20 to 25 percent. Only part of that is explained by being smaller and carrying less tissue. The rest, about 10 to 15 percent beyond what body composition changes account for, comes from your body actively becoming more efficient.
In concrete numbers, a person who lost weight to reach 160 pounds needs roughly 300 to 400 fewer calories per day than someone who has always weighed 160 pounds with the same body composition and activity level. Your muscles literally become better at conserving energy, doing the same physical work with about 20 percent less fuel. Hormonal shifts, particularly drops in thyroid activity and the hunger-regulating hormone leptin, reinforce this efficiency. And this adaptation persists for years, potentially indefinitely, based on studies tracking people six months to seven years after weight loss.
This doesn’t mean maintenance is impossible. It means the formula number is a starting point that needs real-world calibration, especially if you’ve dieted down to your current weight.
What to Eat at Your Calorie Target
Once you have a calorie target, how you fill those calories matters for staying satisfied and keeping your body functioning well. Broadly accepted ranges for adults are 45 to 65 percent of calories from carbohydrates, 20 to 35 percent from fats, and 15 to 25 percent from protein. For a 2,000-calorie maintenance diet, that works out to roughly 225 to 325 grams of carbs, 44 to 78 grams of fat, and 75 to 125 grams of protein.
Protein deserves particular attention for maintenance because it’s the most filling macronutrient per calorie and it supports muscle retention, which in turn protects your metabolic rate. Aiming for the higher end of the protein range, around 20 to 25 percent of total calories, makes it easier to stay at your target without feeling hungry.
How Accurate Is Calorie Tracking
Even with the best intentions, tracking has a built-in margin of error. A meta-analysis of diet-tracking apps found they underestimate calorie intake by an average of about 200 calories per day compared to reference methods. They also tend to undercount fat by about 13 grams and protein by about 12 grams daily. Some of this comes from differences in food databases, and some from the difficulty of accurately estimating portion sizes.
This doesn’t mean tracking is useless. It means you should treat your logged number as an approximation and rely on your actual weight trend over weeks as the true feedback signal. If you’re consistently logging 2,200 calories and your weight is slowly climbing, your real intake is likely higher than what the app says, or your actual TDEE is lower than you estimated. Adjust the number you’re targeting rather than arguing with the scale. Weighing food with a kitchen scale rather than eyeballing portions significantly reduces the gap between what you think you’re eating and what you actually are.