Most people need to eat roughly 500 fewer calories per day than they burn to lose about half a pound to one pound per week. That puts the actual number somewhere between 1,200 and 2,000 calories a day for most adults, depending on body size, age, sex, and activity level. There’s no single magic number, but there is a straightforward way to find yours.
How Your Body Burns Calories
Your body uses energy in three main ways: keeping you alive at rest (breathing, circulating blood, repairing cells), digesting food, and physical activity. The calories burned just to keep your body functioning at rest make up the largest share, typically 60 to 75 percent of everything you burn in a day. This is your basal metabolic rate, or BMR.
Your total daily energy expenditure (TDEE) is your BMR adjusted for how active you are. A desk worker who rarely exercises might only burn 1,800 calories a day, while someone who trains hard most days could burn well over 2,500. To lose weight, you need to consistently eat less than your TDEE.
Finding Your Personal Number
Start by estimating your BMR using one of the standard formulas. The Harris-Benedict equation, widely used in clinical settings, works like this:
- Men: 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) − (5.677 × age in years)
- Women: 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) − (4.330 × age in years)
To convert pounds to kilograms, divide by 2.2. To convert inches to centimeters, multiply by 2.54. So a 40-year-old woman who weighs 170 pounds (77 kg) and stands 5’5″ (165 cm) would have a BMR of roughly 1,470 calories.
Next, multiply your BMR by an activity factor to get your TDEE:
- Sedentary (desk job, little exercise): BMR × 1.2
- Lightly active (light exercise 1–3 days per week): BMR × 1.375
- Moderately active (moderate exercise 3–5 days per week): BMR × 1.55
- Very active (hard exercise 6–7 days per week): BMR × 1.725
If that same woman is lightly active, her TDEE is about 2,020 calories. Subtracting 500 gives her a weight-loss target of roughly 1,520 calories per day.
The 500-Calorie Deficit Rule
The old guideline was simple: cut 3,500 calories per week (500 per day) and lose one pound. The Mayo Clinic now notes this isn’t accurate for everyone. In practice, cutting 500 calories a day leads to about half a pound to one pound lost per week, not a guaranteed full pound. The discrepancy comes from changes in your metabolism as you lose weight.
For faster results, cutting 500 to 750 calories per day can push losses closer to 1 to 2 pounds per week, which is the rate most medical guidelines consider sustainable. Going much beyond that rarely works long-term and can trigger problems that make the whole effort backfire.
Why Very Low Calories Stall Progress
When you slash calories too aggressively, your body fights back. Researchers call this adaptive thermogenesis: your metabolism drops by more than you’d expect from the weight you’ve lost. In one study, participants on a calorie-restricted diet saw their daily energy expenditure fall by an average of 178 calories beyond what their lost body mass would account for, and that happened within just the first week. Hormones that regulate metabolism, appetite, and fat storage all shift in directions that slow weight loss and increase hunger.
What makes this especially frustrating is that the response is consistent. People whose metabolism dropped the most in the first week continued showing the largest drops weeks later. A 100-calorie-per-day greater metabolic slowdown in week one predicted about 4.4 pounds less weight loss over six weeks. In other words, the harder you push with extreme restriction, the harder your body pushes back.
This is why most nutrition professionals discourage diets below 1,200 calories for women or 1,500 for men without medical supervision. At those levels, it becomes very difficult to get adequate vitamins, minerals, and the protein your body needs to preserve muscle.
What to Eat Within Your Calorie Budget
The number of calories matters, but so does where those calories come from. The federal dietary guidelines recommend getting 45 to 65 percent of calories from carbohydrates, 20 to 35 percent from fat, and 10 to 35 percent from protein. During weight loss, pushing protein toward the higher end of that range pays off significantly.
Research on people losing weight through calorie restriction found that eating at least 1.2 grams of protein per kilogram of body weight per day helped protect against muscle loss. For a 170-pound person, that’s about 93 grams of protein daily, roughly equivalent to a chicken breast at lunch, a serving of Greek yogurt, and a palm-sized portion of fish at dinner. Losing muscle during a diet further slows your metabolism, so preserving it keeps your calorie-burning engine running closer to normal.
Protein also keeps you fuller for longer, which makes sticking to a deficit noticeably easier. Fiber-rich vegetables, whole grains, and healthy fats round out a pattern that keeps hunger manageable without requiring you to count every gram.
Adjusting as You Lose Weight
The calorie target you start with won’t stay accurate forever. A smaller body burns fewer calories, both at rest and during exercise. Someone who loses 20 pounds will have a lower BMR than when they started, which means the same 1,500-calorie diet that created a deficit initially may eventually become closer to maintenance. Recalculating every 10 to 15 pounds lost keeps your deficit effective.
Adding physical activity helps in two ways. It increases the number of calories you burn, letting you eat a bit more while still losing weight, and it builds or preserves muscle tissue that keeps your resting metabolism higher. Even moderate movement like brisk walking for 30 minutes most days makes a measurable difference in both the rate of loss and how sustainable the process feels.
Quick Reference by Body Type
These are rough starting points, not prescriptions. Your actual number depends on the calculation above, but they give you a general sense of the range:
- Smaller, less active women: 1,200 to 1,400 calories per day
- Average-sized, moderately active women: 1,400 to 1,600 calories per day
- Smaller or sedentary men: 1,600 to 1,800 calories per day
- Larger or more active men: 1,800 to 2,200 calories per day
If you find yourself consistently hungry, irritable, or losing more than 2 pounds per week after the first couple of weeks, your target is likely too low. The first week or two often shows a larger drop due to water loss, which is normal. After that, steady losses of 0.5 to 1.5 pounds per week signal a sustainable pace.