Daily calories you need
How many calories you burn a day given your body and your activity, and the figure that matches each goal. Using the real 7,700 kcal per kilo, not the rounded "500 a day".
Your figures
Result
- Basal metabolic rate (kcal)
- 1,724
- Lose half a kilo a week (kcal)
- 2,122
- Lose a kilo a week (kcal)
- 1,572
- Gain half a kilo a week (kcal)
- 3,222
What you would burn at each activity level
| Level | Factor | Calories a day |
|---|---|---|
| Sedentary (little or no exercise) | 1.200 | 2,069 |
| Light (1-3 days a week) | 1.375 | 2,370 |
| Moderate (3-5 days a week) | 1.550 | 2,672 |
| Hard (6-7 days a week) | 1.725 | 2,973 |
| Very hard (physical job or two sessions a day) | 1.900 | 3,275 |
What we assume
- Uses the Mifflin-St Jeor formula, now preferred over Harris-Benedict.
- A kilo of body fat is counted as 7,700 kcal.
- The activity factor is a coarse estimate: it does not measure your particular week.
- The formula is accurate on average, with individual variation of around 10%.
How it is calculated
The calculation runs in two steps. First the basal metabolic rate, which is what you would burn lying down all day, just keeping the body running:
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 (men)
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161 (women)
Then it is multiplied by an activity factor, from 1.2 if you barely move to 1.9 if you work physically or train twice a day. The result is your total daily burn.
From calories to kilos
A kilo of body fat stores about 7,700 kcal. Divided across seven days, losing half a kilo a week calls for a deficit of 550 kcal a day, and a full kilo calls for 1,100.
The "500 calories a day" figure repeated everywhere comes from rounding 7,700 down to 7,000. It is not a serious error, but we would rather use the real constant and say where it comes from.
Why Mifflin-St Jeor and not Harris-Benedict
Harris-Benedict dates from 1919 and was derived on people leaner and more active than today's average, so it overestimates by 5 to 15%. Mifflin-St Jeor, from 1990, is what current dietetic guidelines recommend.
What to do with the number
Treat it as a starting point, not a truth. Individual variation runs around 10%, which in this example is nearly 270 calories. What turns the estimate into something useful is eating that figure for two or three weeks and correcting against the scale: if your weight does not move, your real burn is whatever you are eating.
An example
A man of 35, 80 kg and 1.75 m with moderate activity has a basal metabolic rate of 1,724 kcal and a total burn of 2,672. To lose half a kilo a week he would eat 2,122, and to gain one, 3,222.
Frequently asked questions
Can I eat below my basal metabolic rate?
Occasionally it does no harm, but as a sustained plan it is a bad idea: vitamins and minerals get hard to cover, and muscle goes along with the fat. If your goal demands going that low, stretching the timeline or raising your burn with activity works better.
Why does the activity factor jump so much?
Because it is an acknowledged simplification. Between 1.55 and 1.725 there are about 300 calories, and most people fall between two steps. If in doubt, pick the lower one: almost everybody overestimates how much they move.
Does it include my exercise or do I add that on top?
It is already inside the activity factor, so do not add it twice. That is the most common mistake: choosing "hard" and then adding whatever the watch says on top.
Does it work if I carry a lot of muscle?
It reads slightly low. Mifflin-St Jeor uses total weight, and muscle burns more at rest than fat does. For extreme body compositions the Katch-McArdle formula, which starts from lean mass, fits better.
Keep calculating
All tools →- Body mass index calculator BMI is a one-line number that gets used constantly and understood rarely. Here it comes with the weight range for your height, and with the part the formula misses.
- Ideal weight for your height There is no ideal weight, there are four formulas that give four different numbers. Here they are together, with the BMI range alongside, so the real spread is visible.
- Body fat percentage A tape measure and three measurements give a body fat estimate that says considerably more than BMI, because this one does know what your weight is made of.
Updated on 2026-09-10. Calculations run in your browser; nothing you type is sent to a server.