Calorie Calculator: Basal Metabolic Rate and Daily Needs
How many calories your body needs each day depends on four things: sex, age, height and weight, and then on how much you move. The calculator below first works out your basal metabolic rate, the energy your body uses at complete rest, then your daily expenditure at your activity level, and finally how many calories to eat if you want to lose or gain weight. Below the calculator you will find the formula, how large a deficit makes sense, and why for some people the numbers give no result despite discipline.
Calorie calculator
Estimate by the Mifflin-St Jeor formula for adults. Not valid in pregnancy or while breastfeeding.
How the calculator works
The first step is the basal metabolic rate, BMR for short: the energy the body uses in 24 hours of complete rest, on breathing, the heartbeat, keeping warm and running the organs. For most people that is 60 to 70 percent of total daily expenditure. The calculator uses the Mifflin-St Jeor formula from 1990, which has proved more accurate in clinical practice than the older Harris-Benedict one:
- Men: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
- Women: 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
The second step multiplies by an activity factor to get total daily energy expenditure, TDEE for short. A factor of 1.2 applies to someone who sits all day and does not train, 1.55 to someone who trains three to five times a week, and 1.9 to a physical job plus regular training. The most common mistake is overestimating activity: two light sessions a week with a desk job is light activity, not moderate.
| Example | Basal metabolic rate | Daily expenditure |
|---|---|---|
| Woman, 35, 165 cm, 68 kg, light activity | 1,375 kcal | 1,891 kcal |
| Woman, 50, 165 cm, 68 kg, light activity | 1,300 kcal | 1,788 kcal |
| Man, 35, 180 cm, 85 kg, moderate activity | 1,805 kcal | 2,798 kcal |
| Man, 60, 180 cm, 85 kg, desk job | 1,680 kcal | 2,016 kcal |
How large a deficit makes sense
A kilogram of fat tissue holds roughly 7,000 calories, so a deficit of 500 calories a day gives about half a kilogram a week. That is the pace that holds up best in practice: fast enough to see results, slow enough not to lose muscle and not to let hunger take over. A 250-calorie deficit is slower, but many people keep it up for months more easily, which in the end beats crash diets that last three weeks.
There is also a lower limit. An intake below 1,200 calories for women and 1,500 for men rarely provides enough protein, iron, calcium and vitamins, slows the metabolism and almost always ends in regaining the weight. Going below that limit is only done under medical supervision. If the calculator shows a number below it for the 500-calorie deficit, choose the gentler deficit and add movement instead of cutting food further.
During weight loss protein intake should be higher than usual, about 1.2 to 1.6 grams per kilogram of body weight a day, because protein preserves muscle and keeps you full longest. The remaining calories are split between carbohydrates and fats according to habits and tolerance, and there is no universal ratio that suits everyone.
Why the number is only a starting point
The formula has an error of around ten percent and misses by more in some people. Once you have kept to the calculated intake for two weeks, the scale is the only real check. If your weight stays put, cut 100 to 150 calories or add movement; if it drops faster than a kilogram a week, the intake is too low. The body also adapts: after every five or six kilograms lost, expenditure falls, so the number should be recalculated with the new weight.
The formula also does not know how much muscle you have. Two people of the same height and weight can have basal metabolic rates that differ by 200 to 300 calories purely because of muscle mass. That is why strength training during weight loss is not an extra but part of the plan: it preserves muscle, and with it expenditure.
When the deficit does not work: hormones
If you have held a deficit for more than a month, counted honestly, kept moving, and the scale does not respond, the problem is usually not your discipline. Several conditions slow expenditure or make the body hold on to fat despite reduced intake:
- Underactive thyroid. Low thyroid hormone lowers the basal metabolic rate by 10 to 20 percent, with tiredness, feeling cold and dry skin. Detected through TSH and FT4.
- Insulin resistance. High insulin blocks fat breakdown and increases hunger, especially for sweets. Estimated from fasting glucose and insulin via the HOMA index.
- Polycystic ovary syndrome. In women it goes with irregular cycles, acne and excess hair, and almost always with insulin resistance.
- Menopause and perimenopause. Falling oestrogen redirects fat to the waist and reduces expenditure, so the same intake that was fine for years suddenly becomes a surplus.
- Cortisol, sleep and medicines. Chronic stress, short sleep and medicines such as corticosteroids, some antidepressants and diabetes drugs change both appetite and expenditure.
All of this is checked with one set of tests and an endocrinologist consultation. Once the cause is found and treated, the same deficit that gave nothing for months starts to work. We have written about how individual hormones act on weight in how hormones affect weight and metabolism.
Prices
| Service | Price |
|---|---|
| Endocrinologist consultation | from 7,000 RSD |
| Endocrinology consultation with thyroid ultrasound | from 12,000 RSD |
| General practitioner consultation | 4,000 RSD |
Frequently asked questions
How many calories a day should I eat?
As many as your daily expenditure if you want to keep your weight, about 500 fewer if you want to lose half a kilogram a week, and 300 to 500 more if you want to gain. The exact number depends on sex, age, height, weight and activity, and the calculator at the top of the page gives it.
What is the basal metabolic rate?
The energy the body uses at complete rest, on the heartbeat, breathing, keeping warm and running the organs. In adults it is most often between 1,200 and 2,000 calories a day and makes up about two thirds of total expenditure.
How large a calorie deficit is safe?
A deficit of 250 to 500 calories a day, with an intake that does not fall below 1,200 calories for women and 1,500 for men. A larger deficit loses muscle, slows the metabolism and as a rule ends in regaining the weight.
Why am I not losing weight even though I am in a deficit?
First check the deficit is real: unmeasured meals, oil and drinks easily add 300 to 500 calories a day. If it is real and your weight has not moved for more than a month, check your thyroid, fasting insulin and glucose, because an underactive thyroid and insulin resistance block weight loss despite a deficit.
Is the calculator accurate for everyone?
The formula has an error of around ten percent and does not apply in pregnancy, breastfeeding, to children or to people with a large muscle mass. The number is a starting point to check on the scale after two weeks and adjust.
Book an appointment
If the deficit is not working or you suspect a hormone is behind your weight, book an endocrinologist consultation at Miren Medic. Hormone tests, thyroid ultrasound and a treatment plan are all done in one place, without a referral.
