How Many Calories Should I Eat Per Day?
MacroChat Team
AI Nutrition Tracking
The average adult needs roughly 2,000 calories per day, but individual needs vary significantly based on age, sex, height, weight, and activity level. According to the Dietary Guidelines for Americans, women generally need 1,600 to 2,400 calories per day and men need 2,000 to 3,000 calories per day.
That's a wide range. This article will help you find your specific number using evidence-based formulas, and explain how to adjust it for weight loss, muscle gain, or maintenance.
Daily Calorie Needs by Age, Sex, and Activity Level
The following tables are based on the Dietary Guidelines for Americans, 2020-2025 (USDA/HHS). They provide estimated calorie needs for weight maintenance.
Estimated Daily Calories for Women
| Age | Sedentary | Moderately Active | Active |
|---|---|---|---|
| 19-30 | 1,800-2,000 | 2,000-2,200 | 2,400 |
| 31-50 | 1,800 | 2,000 | 2,200 |
| 51+ | 1,600 | 1,800 | 2,000-2,200 |
Estimated Daily Calories for Men
| Age | Sedentary | Moderately Active | Active |
|---|---|---|---|
| 19-30 | 2,400-2,600 | 2,600-2,800 | 3,000 |
| 31-50 | 2,200-2,400 | 2,400-2,600 | 2,800-3,000 |
| 51+ | 2,000-2,200 | 2,200-2,400 | 2,400-2,800 |
Activity level definitions from the guidelines:
- Sedentary: Only light physical activity associated with typical daily life (desk job, minimal exercise).
- Moderately active: Physical activity equivalent to walking 1.5 to 3 miles per day at 3-4 mph, in addition to daily life activities.
- Active: Physical activity equivalent to walking more than 3 miles per day at 3-4 mph, in addition to daily life activities.
How to Calculate Your Exact Calorie Needs
The tables above are general ranges. For a more personalized number, use the Mifflin-St Jeor equation — the most accurate formula for estimating resting metabolic rate (how many calories your body burns at rest). A 2005 systematic review by Frankenfield et al. found it predicted metabolic rate within 10% of measured values in more people than any other equation tested.
Step 1: Calculate Your Basal Metabolic Rate (BMR)
The Mifflin-St Jeor equation, published in the American Journal of Clinical Nutrition (1990):
- Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
- Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161
Step 2: Multiply by Your Activity Level
Your BMR is the calories you burn at rest. To get your Total Daily Energy Expenditure (TDEE) — the total calories you burn in a day — multiply your BMR by an activity factor:
| Activity Level | Multiplier | Description |
|---|---|---|
| Sedentary | 1.2 | Desk job, little or no exercise |
| Lightly active | 1.375 | Light exercise 1-3 days/week |
| Moderately active | 1.55 | Moderate exercise 3-5 days/week |
| Very active | 1.725 | Hard exercise 6-7 days/week |
| Extra active | 1.9 | Very hard exercise + physical job |
Worked Example
A 30-year-old woman, 5'6" (167 cm), 150 lbs (68 kg), who exercises moderately 3-4 days per week:
- BMR = (10 × 68) + (6.25 × 167) − (5 × 30) − 161 = 680 + 1,044 − 150 − 161 = 1,413 calories/day
- TDEE = 1,413 × 1.55 = ~2,190 calories/day
This is her estimated maintenance calories — the amount she'd eat to maintain her current weight. For an instant calculation, use our free macro calculator.
Calories for Weight Loss
To lose weight, you need to eat fewer calories than you burn (a calorie deficit). The National Heart, Lung, and Blood Institute (NHLBI) recommends a deficit of 500 to 1,000 calories per day to produce a weight loss of 1 to 2 pounds per week.
Using our example above (TDEE of 2,190):
- Moderate deficit (500 cal): 2,190 − 500 = 1,690 calories/day → ~1 lb/week loss
- Aggressive deficit (1,000 cal): 2,190 − 1,000 = 1,190 calories/day → ~2 lbs/week loss
The CDC notes that "people who lose weight at a gradual, steady pace — about 1 to 2 pounds a week — are more likely to keep the weight off than people who lose weight quicker."
A few guidelines for setting your deficit:
- Women should generally not go below 1,200 calories; men should not go below 1,500 calories without medical supervision. Very low calorie diets can cause nutrient deficiencies and muscle loss.
- A 500-calorie deficit is sustainable for most people. Larger deficits work faster but are harder to maintain and carry more risk of muscle loss.
- Protein intake matters more during a deficit. Eating at least 0.7-1.0 g of protein per pound of body weight helps preserve muscle mass. Read our protein guide for details.
For a deeper dive into creating and sustaining a calorie deficit, see our complete calorie deficit guide.
Calories for Muscle Gain
To build muscle, you generally need a calorie surplus — eating more than you burn. A surplus of 200 to 500 calories per day is enough for most people to support muscle growth without excessive fat gain.
Using our example (TDEE of 2,190):
- Lean bulk (200-300 cal surplus): 2,390-2,490 calories/day
- Standard bulk (500 cal surplus): 2,690 calories/day
Protein is even more important when building muscle. Aim for 0.7-1.0 g per pound of body weight and prioritize resistance training.
Does Metabolism Really Slow Down with Age?
You've probably heard that your metabolism crashes in your 30s. The science says otherwise.
A landmark 2021 study in Science analyzed metabolic data from 6,619 people aged 8 days to 95 years across 29 countries. The findings identified four metabolic life stages:
- Infancy (0-1 year): Metabolism peaks at about 50% above adult levels.
- Youth (1-20 years): Metabolism gradually declines to adult levels.
- Adulthood (20-60 years): Metabolism remains stable. No significant decline.
- Older adulthood (60+ years): Metabolism declines at about 0.7% per year. By the 90s, total energy expenditure is roughly 26% below middle-aged values.
The takeaway: middle-age weight gain is primarily driven by changes in activity and diet, not metabolic decline. The real metabolic slowdown doesn't begin until after 60.
Why Your Calorie Needs Can Change Over Time
Even with a stable metabolism, several factors can change how many calories you need:
- Weight change: As you lose weight, your body requires fewer calories to maintain its smaller size. A person who loses 30 lbs may need 200-300 fewer calories than before. Recalculate every 10-15 lbs.
- Activity changes: Starting or stopping an exercise program can shift your needs by several hundred calories.
- Metabolic adaptation: When you diet for an extended period, your body can reduce its energy expenditure below what formulas predict. A 2016 study following The Biggest Loser contestants found their metabolisms were burning roughly 500 fewer calories per day than expected 6 years after the competition, even after regaining much of the weight (Fothergill et al., Obesity, 2016). This is an extreme example — these contestants lost weight very rapidly — but it illustrates why gradual weight loss and diet breaks can be valuable strategies.
How to Track Your Calories
Knowing your calorie target is step one. Actually hitting it consistently is step two. Here are the most effective methods, from most to least accurate:
- Food scale + tracking app: The gold standard. Weigh your food and log it. Most accurate but requires the most effort.
- AI-powered tracking: Log meals by voice, photo, or natural language text. Less precise than a food scale but dramatically faster. Good for most people. See our comparison of AI nutrition apps.
- Hand portion method: Use your palm (protein portion), fist (carb portion), thumb (fat portion) as rough guides. Least accurate but requires no tools.
Calculate Your Calories with AI
Use our free macro calculator to get your personalized calorie and macro targets in seconds. Then try MacroChat free for 3 days to track your calories effortlessly with AI — log meals by voice, photo, or text and see exactly where you stand every day.
Sources
- U.S. Department of Agriculture and U.S. Department of Health and Human Services. "Dietary Guidelines for Americans, 2020-2025." 9th Edition, December 2020. Read guidelines
- Mifflin MD, St Jeor ST, et al. "A new predictive equation for resting energy expenditure in healthy individuals." American Journal of Clinical Nutrition, 1990. Read study
- Frankenfield D, et al. "Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review." Journal of the American Dietetic Association, 2005. Read review
- National Heart, Lung, and Blood Institute. "Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults." NIH Publication No. 98-4083, 1998. Read guidelines
- Centers for Disease Control and Prevention. "Steps for Losing Weight." View page
- Pontzer H, et al. "Daily energy expenditure through the human life course." Science, 2021. Read study
- Fothergill E, et al. "Persistent metabolic adaptation 6 years after ‘The Biggest Loser’ competition." Obesity, 2016. Read study