"Eat 2,000 calories a day" is printed on food labels all over the world. The problem is that it's an average — and almost nobody is exactly average. A tall, active 25-year-old man and a petite 55-year-old woman with a desk job can need over a thousand calories a day apart.
The good news is that you can get a far better estimate for yourself in about a minute. It comes down to two numbers: BMR and TDEE.
BMR: what your body burns doing nothing
Your Basal Metabolic Rate is the energy your body uses at complete rest. Even lying in bed all day, you burn calories to breathe, pump blood, keep warm and keep your brain and organs running. For most adults, BMR accounts for the biggest share of daily energy use.
The most widely recommended formula for estimating it is the Mifflin-St Jeor equation:
- Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
- Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
TDEE: what you actually burn in a day
Your Total Daily Energy Expenditure adds everything on top of BMR — walking to the shop, climbing stairs, workouts, fidgeting and even digesting food. It's estimated by multiplying your BMR by an activity factor:
| Activity level | Multiplier |
|---|---|
| Sedentary (desk job, little exercise) | 1.2 |
| Lightly active (exercise 1–3 days a week) | 1.375 |
| Moderately active (exercise 3–5 days a week) | 1.55 |
| Very active (exercise 6–7 days a week) | 1.725 |
| Extra active (physical job or training twice a day) | 1.9 |
TDEE is your maintenance calories — eat about this much and your weight should stay roughly the same.
One honest tip: most people overestimate how active they are. If you work at a desk and go to the gym three times a week, "lightly" or "moderately" active is usually closer to the truth than "very active".
A worked example
Meet Sara: 35 years old, 165 cm tall, 68 kg, and she exercises about four times a week.
Step 1 — BMR:
10 × 68 + 6.25 × 165 − 5 × 35 − 161 = 680 + 1,031 − 175 − 161 = about 1,375 calories
Step 2 — TDEE:
1,375 × 1.55 (moderately active) = about 2,130 calories a day
So Sara maintains her weight on roughly 2,130 calories a day — not 2,000, and certainly not the 1,200 she might see recommended online.
How many calories to lose weight
To lose weight, you need to eat a little less than your TDEE. A common rule of thumb is that a deficit of about 7,700 calories equals roughly 1 kg of body fat (about 3,500 calories per pound). In practice:
- 250 calories below TDEE → roughly 0.25 kg (½ lb) per week. Slow, and very sustainable.
- 500 calories below TDEE → roughly 0.5 kg (1 lb) per week. A good pace for most people.
For Sara, that means around 1,630–1,880 calories a day to lose weight steadily.
Real life isn't perfectly linear. Water weight swings, hormones and changes in daily movement all play a part, and your TDEE drops slightly as you get lighter. Track your weight for two or three weeks, look at the trend rather than day-to-day numbers, and adjust.
How many calories to gain weight or muscle
Flip it around: eat 250–500 calories above your TDEE. If your goal is muscle rather than just weight, pair the surplus with strength training and enough protein. Smaller surpluses tend to add less fat along the way.
Mistakes that stall progress
- Cutting too hard. Very low calorie diets are difficult to stick to, can leave you tired and hungry, and make it harder to get enough nutrients. As a general guide, don't go below about 1,200 calories (women) or 1,500 calories (men) a day without medical supervision.
- Forgetting the small stuff. Cooking oil, sugary drinks, sauces and "just a bite" add up quickly.
- Never recalculating. As your weight changes, so does your TDEE. Re-run the numbers every 4–5 kg.
- Obsessing over precision. Any formula is an estimate, typically within about 10%. Use it as a starting point, then let your results guide you.
Work out your numbers
The free Calorie Calculator does all of this for you: enter your age, sex, height, weight and activity level to see your BMR, your maintenance calories and targets for losing or gaining weight, in kg or lb.
While you're at it, you might find these useful:
- BMI Calculator — check whether your weight is in the healthy range for your height
- Ideal Weight Calculator — compare four medical formulas for a target weight
- Body Fat Calculator — estimate body fat with just a tape measure
Disclaimer: This article is general information, not medical advice. If you're pregnant, breastfeeding, have a medical condition or take medication, talk to a doctor or registered dietitian before changing your diet.