fotorieCalculate daily calories: how many to eat per day
Enter your data and you will see your basal metabolic rate, your maintenance calories, and those corresponding to your goal. No registration required and as a guiding reference for adults.
Guiding estimate for adults. Not indicated during pregnancy or lactation; if you have an illness or need an individual guideline, consult a professional. About the limitations of weight planners (NIDDK).
The calculation is below the limit of this tool. That limit is shown, which does not guarantee adequate intake for you. Consult a professional before using it as a goal.
Mifflin-St Jeor formula. Guiding result: in pregnancy, lactation, under 18 years of age, or with a diagnosed illness, the number must be set by a professional.
What is basal metabolic rate
Basal metabolic rate (BMR) is the energy your body expends at complete rest: breathing, maintaining temperature, making your heart beat, repairing tissues. For most people, it accounts for between 60% and 70% of everything they burn in a day. That’s why it weighs so heavily in the calculation and why two people with the same training can need very different numbers.
Two things are added to BMR: physical activity, which includes both workouts and the steps you take without realizing it, and the thermic effect of food, which is the energy it costs to digest what you eat. All together forms the total energy expenditure, which in apps and consultations is called maintenance calories: if you eat just that, your weight stays where it is.
Calculating daily calories is, at its core, estimating that maintenance and then deciding how far you want to deviate from it. Eating below produces weight loss; eating above, gain. We will see the reasonable distance below and, in more detail, in the calorie deficit calculator.
The formula, with an example
The calculator uses the Mifflin-St Jeor equation, published in 1990 and since validated as the most accurate for healthy adults. It is what we use at Fotorie and what the team of Vitasane nutritionists applies as a starting point in consultation.
Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161
Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5
Then BMR is multiplied by an activity factor: 1.2 if your day is sedentary; 1.375 if you walk and train lightly one to three times a week; 1.55 with three to five workouts; 1.725 if you train almost daily or your job is physical; and 1.9 only for athletes with intense loads every day.
Step-by-step example
A 35-year-old woman, 70 kg and 165 cm tall, with light activity:
- BMR = 10 × 70 + 6.25 × 165 − 5 × 35 − 161 = 700 + 1,031 − 175 − 161 = 1,395 kcal.
- Maintenance = 1,395 × 1.375 = 1,918 kcal per day.
- If she wants to lose half a kilo per week, she subtracts about 550 kcal: 1,368 kcal. Although it exceeds the reference threshold of 1,200 kcal, this does not guarantee that it is an appropriate goal for that person.
The calculator above performs exactly these calculations, which is why the results you see when loading the page match this example.
Guiding table by age, sex, and activity
These figures are maintenance calories for an average height and weight in Spain (woman 163 cm and 66 kg; man 176 cm and 80 kg). They serve to orient you; your individual estimate comes from the calculator.
| Age | Sedentary woman | Active woman | Sedentary man | Active man |
|---|---|---|---|---|
| 20-29 years | 1,700 kcal | 2,200 kcal | 2,200 kcal | 2,850 kcal |
| 30-39 years | 1,650 kcal | 2,100 kcal | 2,150 kcal | 2,750 kcal |
| 40-49 years | 1,600 kcal | 2,050 kcal | 2,050 kcal | 2,650 kcal |
| 50-59 years | 1,550 kcal | 1,950 kcal | 2,000 kcal | 2,550 kcal |
| 60-69 years | 1,500 kcal | 1,900 kcal | 1,900 kcal | 2,450 kcal |
Sedentary is equivalent to factor 1.2 and active to factor 1.55. Notice that age subtracts little, about 50 kcal per decade, while going from sedentary to active adds between 400 and 600 kcal. Moving more gives you much more leeway than aging takes away.
How to put calories into practice
Knowing your number is the first step. The second is to convert it into real meals without life revolving around a kitchen scale.
- Distribute before eating. With 1,900 kcal, a comfortable distribution is 400 for breakfast, 650 for lunch, 550 for dinner, and 300 between two snacks. You don’t have to hit it exactly; you just need to make sure no meal takes up half the day without you knowing it.
- Prioritize protein. Between 1.6 and 2 g per kg of body weight per day maintains muscle and curbs hunger. How to distribute the rest is in the macro calculator.
- Weigh for a week, then estimate. Weighing food for a few days calibrates your eye. Afterwards, a photo of the dish and a reasonable estimate are enough; the average error of a careful estimate is around 10%, the same as that of the formula.
- Correct with the scale, not with the calculator. Weigh yourself fasting two or three times a week and look at the two-week trend. If it doesn’t move as expected, adjust 100 or 150 kcal. That adjustment is worth more than any formula.
- Leave room for life. A dinner out once a week with 300 extra kcal doesn’t break anything. What breaks the plan is abandoning it on Monday because Saturday wasn’t perfect.
Fotorie does this work for you: it calculates your number upon registration, distributes it in a weekly menu with real recipes, and counts each meal from a photo. In calorie counter we explain how it does it.
Common mistakes when calculating calories
- Overestimating activity. Three spinning classes a week with an office job is light activity, not moderate. Choosing a higher level adds 300 kcal that you don’t expend.
- Subtracting training twice. If the activity factor already accounts for your workouts, don’t then add the calories indicated by your watch. Choose one of the two methods.
- Going too low and too fast. A 1,000 kcal deficit works for two weeks and then takes its toll in hunger, fatigue, and muscle loss. Half a kilo per week is a sustainable pace.
- Forgetting drinks and oils. A glass of wine, two tablespoons of oil, and a sweetened coffee with milk add up to 350 kcal that almost no one tracks.
- Taking the number as fixed. When you lose weight, your maintenance drops. Every 4 or 5 kilos, recalculate.
Frequently asked questions
How many calories should I eat per day?
It depends on your sex, age, weight, height, and activity level. An adult woman with light activity usually needs between 1,800 and 2,100 kcal to maintain her weight; a man, between 2,200 and 2,700. The calculator on this page gives you your number using the Mifflin-St Jeor formula.
What is the difference between BMR and maintenance calories?
Basal metabolic rate (BMR) is what your body expends at absolute rest, just to stay alive. Maintenance calories (total daily energy expenditure or TDEE) add to BMR what you expend moving, exercising, and digesting. The latter is used to decide how much to eat.
Is the Mifflin-St Jeor formula reliable?
It is the best fit for the general population according to the U.S. Academy of Nutrition and Dietetics, with a margin of error of around 10%. Very muscular people or those with a lot of body fat may fall outside this margin; in that case, it is advisable to adjust with the scale after two or three weeks.
Why doesn’t the calculator go below 1,200 or 1,500 kcal?
Below 1,200 kcal for women and 1,500 for men, it is very difficult to cover protein, iron, calcium, and fiber, and the body responds by losing muscle and lowering expenditure. This is the same floor that Fotorie applies and that Vitasane nutritionists use in consultation. If you need less, do so under professional supervision.
Do I have to count calories every day?
You don't have to be exact every day. What works is to have a reference and get close to it most of the week. An app that estimates the calories of a dish from a photo takes away the work of weighing and searching for food.
Make it automatic: photo and done
With Fotorie, you count with a photo of the dish: calories, proteins, carbohydrates, and fats instantly, and an AI coach who makes sure you don’t overdo it or fall short. Free to start.
