How do you calculate your calorie needs?
Your calorie needs are the energy your body uses over 24 hours. Without laboratory equipment they cannot be measured precisely, but for most adults they can be estimated reasonably well in two steps: work out your basal metabolic rate, then account for physical activity.
- Enter your age, your sex, your weight in kilograms and your height in centimetres.
- The calculator applies the Mifflin-St Jeor equation to estimate your basal metabolic rate (BMR), the energy you use at rest.
- Pick the activity level that best describes a typical week: your BMR is multiplied by a factor between 1.2 and 1.9.
- The result is your total daily energy expenditure (TDEE): in theory, the intake that keeps your weight stable.
- To lose or gain weight, start from that number, adjust it, then watch how your weight changes over a few weeks.
Keep in mind that this is a starting estimate. The real test is your weight trend after two or three weeks: if it stays stable while you eat around your TDEE, the estimate fits you.
Basal metabolic rate (BMR) vs total daily energy expenditure (TDEE): what is the difference?
Your basal metabolic rate, or BMR, is the energy your body needs at complete rest just to keep running: breathing, keeping your heart beating, holding your body temperature, renewing cells. For people who are not very active, it is often the largest part of the day's energy use.
Total daily energy expenditure, or TDEE, adds everything you do during the day to your BMR: walking, working, housework, exercise, and even the energy used to digest food. This is the number to steer your eating by.
In other words, BMR answers "how much would I burn lying in bed all day?" and TDEE answers "how much do I burn on a normal day?". For a 30-year-old woman who is 165 cm tall and weighs 60 kg, the estimated BMR is 1,320 kcal, and her TDEE reaches 2,046 kcal if she is moderately active.
What is the Mifflin-St Jeor equation?
Published in 1990 in the American Journal of Clinical Nutrition, the Mifflin-St Jeor equation was derived from measurements of resting energy expenditure in healthy adults. It is now widely used to estimate basal metabolic rate. These are the equations the calculator applies:
Men: BMR = 10 × weight + 6.25 × height − 5 × age + 5
Women: BMR = 10 × weight + 6.25 × height − 5 × age − 161
TDEE = BMR × activity factor
Units
- weight in kilograms (kg)
- height in centimetres (cm)
- age in years
- BMR and TDEE in kilocalories per day (kcal/day)
- activity factor: from 1.2 (sedentary) to 1.9 (extremely active)
Worked example
Take a 30-year-old man who is 178 cm tall and weighs 75 kg. BMR = 10 × 75 + 6.25 × 178 − 5 × 30 + 5 = 750 + 1,112.5 − 150 + 5 = 1,717.5 kcal, or about 1,718 kcal per day at rest.
If he is moderately active (factor 1.55), his TDEE is 1,717.5 × 1.55, about 2,662 kcal per day. To lose weight, a starting point would be around 2,162 kcal, and to gain weight, around 3,162 kcal.
Which activity level should you choose?
The activity factor is the least certain part of the calculation. Choose the level that matches a typical week, not your best week. The days refer to sessions of deliberate exercise, on top of everyday walking and chores.
| Activity level | Factor | Concrete examples |
|---|---|---|
| Sedentary (little or no exercise) | 1.2 | Desk job, commuting by car or public transport, little walking, no regular exercise. |
| Lightly active (1-3 days/week) | 1.375 | Desk job plus one to three sessions a week: a brisk 30 to 45 minute walk, yoga, easy cycling. |
| Moderately active (3-5 days/week) | 1.55 | Three to five sessions a week of running, swimming, strength training or group classes, or a job that keeps you on your feet. |
| Very active (6-7 days/week) | 1.725 | Training almost every day, or a physical job (construction, warehouse work, delivery on foot) combined with a few workouts. |
| Extremely active (athlete) | 1.9 | An athlete training twice a day, an endurance athlete preparing for an event, or hard physical work combined with daily training. |
If you hesitate between two levels, pick the lower one. Overestimating activity is common, and it is easier to add a few calories later than to work out why your weight is not moving.
If your activity varies a lot from week to week, think in terms of a monthly average. And if you wear a fitness watch, treat its calories-burned figures with caution: they are estimates too.
Examples of daily calorie needs
To give a sense of scale, here are the calculator's results for four 30-year-old profiles at three activity levels. Values are rounded to the nearest kcal, and the TDEE column is the intake for maintaining weight.
| Profile | Activity | BMR (kcal) | TDEE (kcal) | Lose, −500 (kcal) | Gain, +500 (kcal) |
|---|---|---|---|---|---|
| Woman, 30, 165 cm, 60 kg | Sedentary | 1,320 | 1,584 | 1,084 | 2,084 |
| Woman, 30, 165 cm, 60 kg | Moderately active | 1,320 | 2,046 | 1,546 | 2,546 |
| Woman, 30, 165 cm, 60 kg | Very active | 1,320 | 2,277 | 1,777 | 2,777 |
| Woman, 30, 165 cm, 70 kg | Sedentary | 1,420 | 1,704 | 1,204 | 2,204 |
| Woman, 30, 165 cm, 70 kg | Moderately active | 1,420 | 2,201 | 1,701 | 2,701 |
| Woman, 30, 165 cm, 70 kg | Very active | 1,420 | 2,450 | 1,950 | 2,950 |
| Man, 30, 178 cm, 75 kg | Sedentary | 1,718 | 2,061 | 1,561 | 2,561 |
| Man, 30, 178 cm, 75 kg | Moderately active | 1,718 | 2,662 | 2,162 | 3,162 |
| Man, 30, 178 cm, 75 kg | Very active | 1,718 | 2,963 | 2,463 | 3,463 |
| Man, 30, 178 cm, 85 kg | Sedentary | 1,818 | 2,181 | 1,681 | 2,681 |
| Man, 30, 178 cm, 85 kg | Moderately active | 1,818 | 2,817 | 2,317 | 3,317 |
| Man, 30, 178 cm, 85 kg | Very active | 1,818 | 3,135 | 2,635 | 3,635 |
Activity weighs more than body weight: for the 60 kg woman, going from sedentary to very active adds 693 kcal per day, while 10 extra kilograms add only 100 kcal to her BMR. For the 75 kg man, the same change in activity is worth 902 kcal per day.
How many calories should you eat to lose weight?
To lose weight, you need on average to take in less energy than you use. A deficit of about 500 kcal per day below your TDEE is a common starting point, and it is the figure the calculator shows in the weight loss box.
A usual approximation is about 7,700 kcal per kilogram of body fat. Eating 500 kcal less per day, or 3,500 kcal per week, works out in theory to a little under half a kilogram per week, about 0.45 kg. That is an order of magnitude, not a promise.
Weight loss is not linear. In the first days the scale often moves faster because of water and digestive contents, then progress slows, plateaus and sometimes goes back up from one day to the next. As you lose weight your energy use also falls, so recalculate your needs from time to time.
Avoid eating below your basal metabolic rate for long periods without medical supervision. A very large deficit is hard to sustain, can contribute to tiredness and muscle loss, and makes it harder to meet your nutrient needs.
Talk to a health professional before changing what you eat if:
- you are pregnant or breastfeeding
- you are under 18
- you have or have had an eating disorder
- you live with a chronic illness or take long-term medication
And to gain weight or muscle?
To gain weight you need the opposite: a small surplus. The calculator shows TDEE plus 500 kcal, but a surplus of 300 to 500 kcal per day is usually enough. Beyond that, a larger share of the weight gained is likely to be fat.
If your goal is to build muscle, a surplus alone is not enough: you also need regular resistance training (weights or bodyweight exercises) and enough protein, spread across the day's meals. A modest surplus and slow progress are easier to keep under control.
As with weight loss, weigh yourself under the same conditions and look at the trend over several weeks. If your weight has not moved after three weeks, add 100 to 200 kcal per day and watch again.
How should you split your calories?
Once your calorie intake is set, the next question is macronutrients: carbohydrates, fat and protein. EFSA, the European Food Safety Authority, has published reference values for adults:
- Carbohydrates: 45 to 60% of energy intake.
- Fat: 20 to 35% of energy intake.
- Protein: a population reference intake of 0.83 g per kilogram of body weight per day.
To turn percentages into grams, remember that 1 g of protein or carbohydrate provides 4 kcal, and 1 g of fat provides 9 kcal.
Example for 2,000 kcal per day
| Macronutrient | Share of energy | kcal | Grams per day |
|---|---|---|---|
| Carbohydrates | 50% | 1,000 | 250 g |
| Fat | 30% | 600 | 67 g |
| Protein | 20% | 400 | 100 g |
The maths: 2,000 × 50% = 1,000 kcal, divided by 4, gives 250 g of carbohydrates. 2,000 × 30% = 600 kcal, divided by 9, gives about 67 g of fat. 2,000 × 20% = 400 kcal, divided by 4, gives 100 g of protein.
Check protein in grams too: for a person weighing 70 kg, 0.83 g/kg is about 58 g per day. The example above is higher, which is fine: the reference intake covers the needs of nearly all healthy adults and is not an upper limit.
These ranges leave room for your tastes and food culture. Quality matters as much as the numbers: vegetables, fruit, whole grains, pulses, varied protein sources and good quality fats.
What are the limits of the estimate?
No equation knows your body better than your own measurements. The calculator's result is a starting estimate to check against reality.
Individual variation
Two people of the same age, height and weight can use different amounts of energy. A gap of around 10% between the Mifflin-St Jeor estimate and measured expenditure is often cited, sometimes more for some people.
Body composition
The equation does not tell muscle from fat. A very muscular person often burns more than predicted, and a person with a lot of body fat sometimes less.
Age and hormones
The equation includes age, but not changes linked to menopause, the menstrual cycle or some hormonal conditions, such as thyroid disorders.
Medication and health
Some medicines, an illness or a period of recovery can change energy expenditure or appetite.
Activity level
The activity factor is an approximation: it sums up a whole week in a single number.
The practical method: eat around your target for two to three weeks, log what you eat and weigh yourself several times a week under the same conditions. If the trend is not going the way you expected, adjust your intake by 100 to 200 kcal per day. Recalculate your needs whenever your weight or activity changes noticeably.
Frequently asked questions
How many calories does a woman need per day?
It depends on age, height, weight and activity. For example, a 30-year-old woman who is 165 cm tall and weighs 60 kg needs about 1,584 kcal per day if she is sedentary, and about 2,046 kcal if she is moderately active. The calculator gives an estimate for your own profile.
How many calories does a man need per day?
For a 30-year-old man who is 178 cm tall and weighs 75 kg, the estimate is about 2,061 kcal per day if he is sedentary, and about 2,662 kcal if he is moderately active. A taller, heavier or more active man needs more.
Is 1,200 calories a day enough?
For many adults, 1,200 kcal a day is close to or below their basal metabolic rate. For example, a 30-year-old woman who is 165 cm tall and weighs 60 kg has an estimated BMR of 1,320 kcal. An intake that low makes it hard to meet nutrient needs and should only be followed with medical supervision. A moderate deficit from your TDEE is usually easier to sustain.
How accurate is the calorie calculator?
It uses the Mifflin-St Jeor equation, which is widely used to estimate the basal metabolic rate of healthy adults. It is still an estimate: a gap of around 10% with real expenditure is often cited, and choosing an activity level adds uncertainty. Track your weight for two to three weeks to fine-tune it.
Does the calculator include exercise?
Yes, through the activity level: your basal metabolic rate is multiplied by a factor ranging from 1.2 for a sedentary person to 1.9 for an athlete. So do not add the calories burned during workouts on top, or they would be counted twice.
What is the difference between BMR and TDEE?
BMR, or basal metabolic rate, is the energy used at complete rest to keep the body running. TDEE, or total daily energy expenditure, adds physical activity, moving around and digestion. TDEE is the number to compare with what you eat.
How can I track my calories day to day?
The simplest way is to log what you eat in a nutrition tracking app. With the Ubod app, you can scan a barcode or take a photo of your plate to estimate the calories and macronutrients of your meals. Even a few weeks of tracking helps you understand your habits.
How many calories do you need to burn to lose 1 kg?
Using the common approximation of about 7,700 kcal per kilogram of body fat, losing 1 kg takes a total deficit of about 7,700 kcal, which is a little over two weeks at 500 kcal less per day. In practice the pace varies with water, muscle mass and how your body adapts.
Sources
- Mifflin MD, St Jeor ST et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51(2):241-247.
- EFSA. Scientific Opinion on Dietary Reference Values for energy (2013).
- EFSA. Dietary Reference Values for nutrients, summary page.
This content is for information only. It does not replace a consultation with a doctor or dietitian.
Updated on 14 September 2026 · Method: Ubod team
