Calorie calculator: how many calories you need a day
Enter your details and the calculator works out how many calories you need each day to hold your current weight. It uses the Mifflin-St Jeor equation — the one dietitians reach for — and shows your resting and total energy expenditure separately.
Calculate
The values below are an example — change them to yours and the result updates instantly.
The Mifflin-St Jeor equation has two published versions — that is a limit of the equation, not an assumption about people.
Result
2,230 kcal
Your daily calorie needs (TDEE)
- Resting metabolic rate (BMR)
- 1,440 kcal
What this calculator actually works out
Your daily calorie need is the energy you get through in twenty-four hours, and it comes in two parts. Basal metabolic rate — BMR — is what your body spends simply existing: pumping blood, breathing, holding its temperature, running your brain. You spend it lying in bed all day, and for most people it is the larger share of the total. Total daily energy expenditure — TDEE — is that BMR multiplied by an activity factor, which adds everything you do on top of lying still: walking, working, training, even digesting the food itself.
The calculator reports both. Eat roughly at your TDEE and your weight holds. Eat under it and you lose weight; eat over it and you gain. That is the whole arithmetic — everything else is execution.
How accurate this number is
Honestly: it is a good approximation, not a measurement. The Mifflin-St Jeor equation was fitted to a large group of people and predicts the average for someone with your characteristics. For any one person, being out by ten percent in either direction is ordinary — on a 2,000 kcal result that is about 200 kcal. The activity multiplier adds far more uncertainty than the equation does: the gap between the light and moderate bands is over 200 kcal a day for a typical person, and nobody rates their own activity objectively. That is why every figure here is rounded to the nearest 10 kcal — a third significant digit would be fiction.
The practical reading: treat this as a starting point, not a verdict. Eat around it for two to three weeks, watch what your weight actually does, then adjust by 100–200 kcal. Two weeks of your own data beats any equation.
What to do with the number
If you want to hold your weight, this is your everyday target. If you want to lose, you need a deficit — but a smaller one than instinct suggests: ten to twenty percent below your TDEE, not half of it. Too large a deficit costs muscle, energy and sleep, and usually ends with the whole plan abandoned inside a month. If you want to gain, the mirror image applies: a modest surplus with enough protein to build with.
The harder problem is not the calculation, though. You now know roughly what you spend — but how much are you actually eating? Food-diary research consistently finds that people underestimate their intake, and substantially so. Not deliberately: the oil in the pan, the milk in the coffee and two biscuits from a colleague's desk simply never make it into the log.
Common questions
What is the difference between BMR and TDEE?
BMR, your basal metabolic rate, is the energy your body needs just to keep running: heartbeat, breathing, body temperature, brain activity. You spend it without getting out of bed. TDEE, total daily energy expenditure, is that BMR plus everything you do during the day — walking, working, training, digesting. TDEE is always the larger of the two, typically by twenty to ninety percent depending on how active your life is. When people talk about “how many calories I need a day”, TDEE is the number they mean.
How many calories should I eat to lose weight?
Start from the TDEE this calculator gives you and take off ten to twenty percent. At a 2,000 kcal requirement that means eating 1,600–1,800 kcal a day, for a loss of roughly 0.25–0.5 kg a week. A bigger cut does not speed things up proportionally, but it does clearly increase how much muscle you lose alongside fat, along with the hit to sleep, mood and training. Never go below your own BMR — that is the energy your body needs for basic function.
Is this calorie calculator free, and do I need an account?
It is free and there is no sign-up. The calculation runs entirely in your browser: nothing you type here is sent to our servers or stored anywhere, so you can close the page and come back whenever you like.
How do I know whether I am actually eating that amount?
That is the right question, because food-diary research shows people underestimate what they eat, often by several hundred calories a day and without meaning to. Olivka counts your food in a chat: send a photo, a voice note, or one line of text on WhatsApp, Messenger, Telegram, or Instagram and you get the calories, the macros and a running daily total back in about ten seconds. No app to install and no account to create.
Sources
- Mifflin MD et al., “A new predictive equation for resting energy expenditure in healthy individuals”, The American Journal of Clinical Nutrition, 1990
- Livingstone MBE & Black AE, “Markers of the validity of reported energy intake”, The Journal of Nutrition, 2003 — on systematic under-reporting in food diaries
- How Olivka counts calories — methodology and data sources
You know the number. The hard part is counting against it.
Olivka adds up your day in the background. Send a photo or one sentence and she does the rest.
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Last updated: 2026-08-20