How many calories do you really need per day?

The short answer: it depends on you. Your daily energy expenditure — the well-known TDEE, short for total daily energy expenditure — adds up your basal metabolic rate (what your body burns at rest, just to stay alive) and everything you move during the day. As a rough guide, that comes to about 1,800 to 2,400 kcal for a woman and 2,200 to 2,900 kcal for a man, from sedentary to active, according to reference values from the European Food Safety Authority (EFSA) — but these ranges are wide, and two people of the same weight can be 500 kcal apart.

The real message: there is no universal "right" number. Your needs depend on your height, your weight, your muscle mass, your age and, above all, how active you are — not just at the gym, but all day long. The good news is that you don't need to guess it perfectly: you start from a decent estimate, then let reality correct course.

What your daily calorie burn is made of

Four components, very unequal:

• Basal metabolic rate (60-70%) — the energy your brain, heart, liver and muscles burn at rest. It's the biggest piece, and it depends mostly on your lean mass.
• Background activity, or NEAT (15-30%) — non-exercise activity: walking, standing, fidgeting, taking the stairs. It's the component that varies most from one person to the next, and the one that explains most of the differences.
• Exercise (5-15%) — often overestimated. A hard workout is 300 to 600 kcal, not 1,500.
• Digestion (~10%) — the energy spent processing what you eat: 5 to 15% of expenditure according to a 2004 review, a bit more when your plate is high in protein.

Calorie formulas: a starting point, not the truth

The most reliable one is the Mifflin-St Jeor equation: a 2005 systematic review found it was the one that most often lands within 10% of measured metabolic rate. For a man: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5; for a woman, the same calculation with −161 at the end (to convert, divide pounds by 2.2 and multiply inches by 2.54). That gives you your basal metabolic rate, which you then multiply by an activity factor: from 1.4 if you're sedentary to 2 if you're very active, according to EFSA.

A concrete example: a 30-year-old man who weighs 75 kg (165 lb) and stands 178 cm (5'10") gets a basal metabolic rate of about 1,720 kcal. Training three or four times a week (factor ~1.5), his total expenditure comes to around 2,580 kcal. But keep this in mind: it's an estimate. Formulas can be off by 200 to 300 kcal either way, because they know neither your actual muscle mass nor how fidgety you are.

How to find your maintenance calories: the scale over 2-3 weeks

It's the only method that doesn't lie. Here's how to turn the estimate into a reliable number:

• Eat roughly at your estimated expenditure for 2 to 3 weeks, without trying to lose or gain weight.
• Weigh yourself in the morning on an empty stomach, and look only at the weekly average — a single day's weight means nothing (water, salt, digestion).
• Stable weight → you've found your maintenance. Weight going up → your real expenditure is lower. Weight going down → it's higher. Adjust by 150-200 kcal and start again.

That's exactly the logic you build on when you want to calculate a calorie deficit properly: you start from your real expenditure, not from a theoretical number.

What affects how many calories you burn

• Your muscle mass. The more muscle you have, the higher your basal metabolic rate, even at rest — one of the long-term benefits of strength training, and a reason to eat enough protein.
• Your background activity. In a study published in Science (2005), people with overweight sat 2 hours more per day than lean people: about 350 kcal less burned per day. Your daily step count often matters more than the workout itself.
• Age. Less than people think: according to a large study published in Science (2021), at equal lean mass, expenditure stays stable from age 20 to 60 and only declines after that. What drops before then is mostly muscle and movement — two things that are partly under your control.
• Sleep and stress. Poor sleep throws off appetite and spontaneous activity, which blurs the calculation around the edges.

Key takeaways

• Your expenditure = basal metabolic rate + activity; as a rough guide, ~1,800-2,400 kcal (women) and ~2,200-2,900 kcal (men), highly variable.
• Formulas like Mifflin-St Jeor give you a starting point within ±200-300 kcal, not the truth.
• The only reliable method: eat at your estimate, track your average weight over 2-3 weeks, adjust.