The Short Answer
Most adults need somewhere between 1,600 and 3,000 calories a day to maintain their weight. Where you fall in that range depends on your sex, size, age and how much you move. To lose weight, you eat a few hundred below that number; to gain muscle, a few hundred above.
That's the honest answer, and it's unsatisfying, because a 500-calorie range is useless for planning a day. The rest of this article turns it into your number in four steps, then covers the mistakes that make people get it wrong.
General Guidelines (Before You Calculate)
The U.S. Dietary Guidelines publish estimated daily calorie needs by age, sex and activity level. They're population averages, not personal targets, but they're a useful sanity check:
| Sedentary | Moderately active | Active | |
|---|---|---|---|
| Women 19–30 | 1,800–2,000 | 2,000–2,200 | 2,400 |
| Women 31–50 | 1,800 | 2,000 | 2,200 |
| Women 51+ | 1,600 | 1,800 | 2,000–2,200 |
| Men 19–30 | 2,400–2,600 | 2,600–2,800 | 3,000 |
| Men 31–50 | 2,200–2,400 | 2,400–2,600 | 2,800–3,000 |
| Men 51+ | 2,000–2,200 | 2,200–2,400 | 2,400–2,800 |
"Sedentary" here means a typical day with only light activity. "Active" means the equivalent of walking more than 5 km a day at a brisk pace on top of daily life. These figures assume average height and weight, which is why a tall, heavy person and a short, light person of the same age get very different real numbers.
Step 1: Estimate Your Resting Calories (BMR)
Basal metabolic rate is what your body burns doing nothing: breathing, circulating blood, maintaining temperature, running your brain. It's the single largest component of daily calorie burn, typically 60–70% of the total.
The Mifflin-St Jeor equation is the formula most dietitians use. A validation study in the Journal of the American Dietetic Association (Frankenfield et al., 2005) found it more accurate than the older Harris-Benedict equation across a range of body sizes.
Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5 Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
Example 1: Woman, 42 years old, 165 cm, 72 kg (10 × 72) + (6.25 × 165) − (5 × 42) − 161 = 720 + 1,031 − 210 − 161 = 1,380 kcal
Example 2: Man, 29 years old, 182 cm, 88 kg (10 × 88) + (6.25 × 182) − (5 × 29) + 5 = 880 + 1,138 − 145 + 5 = 1,878 kcal
Step 2: Multiply by Your Activity Level
BMR is what you burn asleep. Multiply it to get your total daily energy expenditure (TDEE), which is your maintenance calories.
| Activity level | Description | Multiplier |
|---|---|---|
| Sedentary | Desk job, little or no exercise | 1.2 |
| Lightly active | Light exercise 1–3 days a week | 1.375 |
| Moderately active | Moderate exercise 3–5 days a week | 1.55 |
| Very active | Hard exercise 6–7 days a week | 1.725 |
| Extremely active | Physical job plus hard daily training | 1.9 |
Example 1, lightly active: 1,380 × 1.375 ≈ 1,900 kcal to maintain Example 2, moderately active: 1,878 × 1.55 ≈ 2,910 kcal to maintain
The multiplier is where most calculations go wrong. People consistently overrate their activity. Three gym sessions a week plus a desk job and a car commute is "lightly active," not "moderately active." When in doubt, pick the lower level. You'll correct it with real data in Step 4.
Step 3: Adjust for Your Goal
To lose weight
Subtract 300–500 kcal from maintenance. For most people this produces a loss of roughly 0.25–0.5 kg per week, which is fast enough to see progress and slow enough to keep muscle and stay sane.
Larger deficits work in the short term but tend to increase hunger, muscle loss and dropout. A deficit above about 1,000 kcal a day is rarely sustainable and usually counterproductive.
Example 1: 1,900 − 400 = 1,500 kcal/day Example 2: 2,910 − 500 = 2,400 kcal/day
To maintain weight
Eat at your TDEE. If your weight drifts up or down over a few weeks, adjust by 100 kcal.
To gain muscle
Add 200–300 kcal to maintenance, combined with resistance training and adequate protein. Larger surpluses don't build muscle faster; they build fat faster. A realistic muscle-gain rate for most people is 0.1–0.3 kg per week, which a small surplus is enough to support.
Example 2, gaining: 2,910 + 250 = 3,160 kcal/day
The floor
Very low intakes are hard to make nutritionally complete and tend to backfire. Common clinical guidance advises against going below about 1,200 kcal a day for women and 1,500 for men without medical supervision. If your calculated deficit lands below those numbers, use a smaller deficit and accept a slower rate of loss, or add activity instead of cutting more food.
Step 4: Check Against Reality After Two Weeks
Every number above is an estimate. BMR formulas have a typical error of around ±10%, and the activity multiplier adds more uncertainty on top. Your body's actual response is the only reliable measurement.
Track your intake for two weeks, weigh yourself daily, and compare the weekly averages:
| Weekly average weight | On a fat-loss target | On a muscle-gain target |
|---|---|---|
| Down 0.25–0.75 kg/week | On track, keep going | Too low, add 200 kcal |
| Flat | Reduce by 100–150 kcal | Add 100–150 kcal |
| Up 0.1–0.3 kg/week | Reduce by 200–300 kcal | On track, keep going |
| Up faster than 0.5 kg/week | Something's untracked; audit your log | Reduce by 150 kcal |
Adjust once, wait another two weeks, repeat. Within a month or two you'll have a maintenance number based on your own body rather than a formula, and it's usually within 100–200 kcal of the calculated one.
For an explanation of why your weight bounces around day to day during this process, see why your weight fluctuates every day.
Why the Number Changes Over Time
Your calorie needs aren't fixed.
Weight loss lowers them. A smaller body needs fewer calories. As a rule of thumb, recalculate every 5–8 kg lost, or whenever a working deficit stops producing results. This is the most common reason weight loss stalls, which we cover in detail in our weight loss plateau guide.
Age lowers them slightly. Metabolic rate declines gradually, largely because muscle mass declines. Regular resistance training slows this considerably.
Muscle raises them. Each kilogram of muscle adds a modest amount to resting burn. It's not the dramatic effect sometimes claimed, but it adds up over years.
Activity changes them a lot. Non-exercise movement, walking, standing, fidgeting, can differ by hundreds of calories between people and between weeks. A period of sitting more (illness, a busy project, winter) lowers your needs without you noticing.
Common Mistakes
Trusting the calculator over the scale. The formula gets you started. Two weeks of data tells you if it was right. People who insist the calculator is correct while the scale disagrees are the ones who stay stuck.
Eating back exercise calories. Fitness trackers and cardio machines routinely overestimate calories burned, often by 30% or more. If you've already included your training in your activity multiplier, adding exercise calories on top counts them twice. Either use a lower multiplier and eat back a portion of tracked exercise, or use the higher multiplier and ignore exercise calories entirely. Not both.
Underestimating intake. Self-reported food intake is unreliable across the board; research consistently finds people under-report by 20% or more. Weigh calorie-dense foods, log everything including drinks and cooking oil, and remember that labels themselves carry a margin of error, as we explain in how accurate are calorie labels. If manual logging is the reason you stop tracking, lower the friction rather than dropping the habit: photo-based apps like CalSensei estimate calories from a picture of the plate, which makes home-cooked and restaurant meals realistic to capture.
Ignoring protein. Two people eating 1,600 kcal a day will get very different results if one eats 60 g of protein and the other 130 g. Protein preserves muscle during a deficit and controls hunger. Aim for 1.6–2.2 g per kg of body weight when losing fat; the reasoning is in our protein per kg guide.
Cutting too hard, too fast. A 1,000 kcal deficit produces a dramatic first week (mostly water) followed by hunger, poor sleep, worse workouts and, often, a rebound. A 400 kcal deficit is slower and far more likely to still be in place three months later.
Changing the target every few days. A number needs two weeks to show whether it works. Reacting to daily scale changes means you never find out.
Putting It Together
For our two examples:
| Woman, 42, 165 cm, 72 kg, lightly active | Man, 29, 182 cm, 88 kg, moderately active | |
|---|---|---|
| BMR | 1,380 | 1,878 |
| Maintenance (TDEE) | 1,900 | 2,910 |
| Fat loss target | 1,500 | 2,400 |
| Muscle gain target | 2,150 | 3,160 |
| Protein target (fat loss) | ~130 g | ~160 g |
Once you have your calorie target, the next question is how to split it into protein, carbs and fat, which we walk through in our complete guide to tracking macros.
Frequently Asked Questions
How many calories should I eat a day to lose weight?
Roughly 300–500 kcal below your maintenance level. For many women that's around 1,400–1,800 kcal; for many men, 1,800–2,400. Calculate your own maintenance first rather than using a generic number.
How many calories should a woman eat a day?
Most adult women maintain their weight on 1,800–2,200 kcal depending on size and activity, and lose weight on roughly 1,400–1,800. Individual needs vary considerably with height, weight and movement.
How many calories should a man eat a day?
Most adult men maintain on 2,200–3,000 kcal depending on size and activity, and lose weight on roughly 1,800–2,500.
Is 1,200 calories a day enough?
For most adults, no. It's generally considered the lowest intake at which a diet can still be nutritionally adequate, and it's usually only appropriate for smaller, less active women. Very low intakes increase muscle loss and are hard to sustain.
Should I eat back the calories I burn exercising?
Only if your activity multiplier didn't already account for that exercise, and even then only a portion, since trackers overestimate. Counting the same workout twice is a common reason weight loss stalls.
How do I know if my calorie target is right?
Track intake and weight for two weeks and compare weekly averages. A fat-loss target should produce 0.25–0.75 kg of loss per week; if it doesn't, adjust by 100–150 kcal and repeat.
This article is for general educational purposes and is not a substitute for individualized medical or nutritional advice. If you are pregnant, breastfeeding, under 18, have a medical condition, or have a history of disordered eating, consult a qualified healthcare professional before changing your calorie intake.
Sources
- U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020–2025: Appendix 2, Estimated Calorie Needs per Day.
- Mifflin MD, et al. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition, 1990.
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association, 2005.
- Hall KD, et al. Quantification of the effect of energy imbalance on bodyweight. The Lancet, 2011.
- National Heart, Lung, and Blood Institute. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults.
- Lichtman SW, et al. Discrepancy between self-reported and actual caloric intake and exercise in obese subjects. New England Journal of Medicine, 1992.
