How many calories do I need a day? Work it out in 3 steps

There’s no single right number of calories. A 1.60 m office worker and a 1.90 m builder can need a thousand calories a day apart. The good news is that you can get a solid estimate in three steps, then fine-tune it from your own results.

Step 1: your resting burn (BMR)

Your basal metabolic rate (BMR) is roughly what your body burns at complete rest: breathing, keeping warm, running your organs. The most widely used estimate today is the Mifflin-St Jeor equation, published in 1990 and generally found to be the most accurate of the common formulas for healthy adults.

• Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5
• Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161

Example: a 35-year-old woman, 165 cm and 70 kg.

10 × 70 + 6.25 × 165 − 5 × 35 − 161 = 700 + 1,031 − 175 − 161 = about 1,395 kcal

Step 2: multiply by your activity

BMR doesn’t include walking, working, exercise or digesting food. To get your total daily energy expenditure (TDEE), multiply BMR by an activity factor:

Activity level	What it looks like	Multiply BMR by
Sedentary	Desk job, little walking, no exercise	1.2
Lightly active	Light exercise 1–3 days a week, or on your feet a fair bit	1.375
Moderately active	Exercise 3–5 days a week	1.55
Very active	Hard exercise 6–7 days a week	1.725
Extra active	Physical job plus training, or twice-a-day training	1.9

Most people overestimate their activity. If you’re unsure between two levels, pick the lower one; you can always adjust later.

Example continued: she exercises three or four times a week, so 1,395 × 1.55 = about 2,160 kcal a day to maintain her weight.

Step 3: set your target

To lose weight

A kilogram of body fat stores roughly 7,700 calories. To lose about 0.5 kg a week, eat around 550 calories a day below your TDEE (7,700 × 0.5 ÷ 7).

• Losing 0.25 to 0.75 kg a week is a sensible range for most people.
• Faster than about 1% of your body weight a week tends to cost more muscle and is harder to stick with.
• Don’t go below roughly 1,200 kcal a day for women or 1,500 for men without medical supervision. Below that it’s hard to get enough protein and nutrients.

Example: 2,160 − 550 = about 1,610 kcal a day to lose around half a kilo a week.

To maintain

Eat at your TDEE. Your weight will still move up and down day to day; aim for a steady weekly average.

To gain (for example, to build muscle)

Eat 250 to 500 calories a day above your TDEE, and lift weights. A slower gain of about 0.25 kg a week keeps the extra weight leaner.

A second example

A 30-year-old man, 178 cm and 85 kg, who trains four times a week:

• BMR: 10 × 85 + 6.25 × 178 − 5 × 30 + 5 = about 1,818 kcal
• TDEE: 1,818 × 1.55 = about 2,820 kcal
• To lose 0.5 kg a week: 2,820 − 550 = about 2,270 kcal a day

Your estimate is a starting point

Every formula estimates an average person. Your real burn could be 10% higher or lower. So treat your number as a hypothesis and test it:

1. Eat your target consistently for two to three weeks, logging accurately.
2. Weigh yourself a few mornings a week and look at the weekly average, not single days.
3. Compare the trend with what you expected:
   • Losing faster than planned and feeling tired? Add 100 to 200 calories.
   • Weight flat for three weeks? Check your logging first (cooking oil, drinks, weekends), then reduce by 100 to 200 calories.
4. Recalculate after every 4 to 5 kg of change, because a lighter body burns less.

Don’t forget protein

When you eat less, protein helps you hold on to muscle and stay full. A good target while losing weight is around 1.2 to 1.6 g per kilogram of body weight a day. See our guide on how much protein you need.

The shortcut

Real Calorie Tracker’s goal calculator uses exactly this method: Mifflin-St Jeor, the activity factors above, your weekly goal, and the same minimums. Enter your details once, apply the suggested calories and macros, and then log your meals to see how close you get each day.