Calorie calculator: how many calories a day?
Six fields, and you get the daily calorie target and the three macros that go with it. Everything is worked out in your browser: nothing you type here is sent anywhere, stored, or saved in the address bar.
Your daily target
2,720kcal a day
Basal metabolic rate 1,755 kcal, maintenance 2,720 kcal at activity factor 1.55.
Macros
- Protein130 g19 % of energy
- Carbs410 g60 % of energy
- Fat65 g21 % of energy
These are estimates from the Mifflin-St Jeor equation, not measurements of you. Use the number as a starting point and let a few weeks of your own weight data correct it.
Calculated in your browser. Nothing you type is sent to a server, written into the address bar, or stored on your device.
This is not health advice. Pregnancy, breastfeeding, an illness, medication that affects weight or appetite, or a history of an eating disorder all belong with a professional rather than a web page.
This is the same daily target Wellboy keeps for you, every day, once you set it in the app.
Where the number comes from
Your body spends energy even when you do nothing: breathing, heartbeat, body temperature, the upkeep of every cell. That baseline is called basal metabolic rate, and this calculator estimates it with the Mifflin-St Jeor equation from weight, height, age and sex. It is one of the ordinary equations for this, and it produces an estimate, not a measurement.
The second step multiplies that baseline by an activity factor between 1.2 and 1.9, covering everything you do on top of lying still: walking, standing at work, training. The result is your maintenance level: roughly the intake at which your weight stays put.
The last step applies the goal. A 500 kcal daily deficit is the step usually called half a kilo a week, because the rule of thumb puts roughly 7,700 kcal in a kilo of body fat. It is a rule of thumb, not a law.
What the activity levels actually mean
This is the input people get wrong, and it moves the result more than any other: for one body, sedentary and extremely active sit over a thousand calories apart. Pick the level that matches an ordinary week, not the week you wish you had.
Sedentary is a desk job and little else. Lightly active is daily walks or exercise one to three times a week. Moderately active is being on your feet a lot, or training three to five times a week, which is what most ready-made workout weeks assume. Very active is a physical job or hard training six or seven times a week. Extremely active is hard daily training on top of physical work, and almost nobody with a desk job belongs there.
Between two levels, take the lower one. An overestimated activity level is the most common reason a calorie target quietly stops working: it looks fine on the page and does nothing in real life.
Why protein is set per kilo
Calories decide what happens to your weight. Protein has a lot to say about whether that change is muscle or fat. That is why the calculator sets protein per kilo of body weight rather than as a share of calories: a percentage of a small target is a small amount of protein, exactly when you have the least room for error.
The steps are 2.0 g per kilo while losing, 1.8 g while building and 1.6 g at maintenance: ordinary numbers for someone doing strength training, aimed at keeping muscle while the scale moves.
Fat then takes the higher of 0.8 g per kilo or a fifth of your calories, because cutting it to nothing is miserable. Carbohydrates take whatever is left, which is why they swing the most between goals. If hitting the protein figure is the hard part, the recipe library is the practical end of this.
The floor under the result
This calculator will not hand you a target below your own basal metabolic rate, and never below 1,500 kcal for men or 1,200 for women, whichever is higher. If your goal would have gone under that line, the result is raised to the floor and the page says so rather than quietly swapping the number.
Very low intakes are not a faster version of the same thing: they are hard to hold, they take muscle along with the fat, and the versions that work are supervised rather than run off a web page.
If your maintenance level is so low that a normal deficit hits the floor, the useful lever is the other one: moving more raises maintenance itself, which makes the same deficit easier to live with.
What to do when the scale does not move
Give it two to three weeks before judging anything. Body weight swings by a kilo or more from water, salt, sleep and what is still in your gut, so a single morning tells you almost nothing and the average of a week tells you a lot. Weigh yourself the same way each time: same time of day, after the toilet, before breakfast.
Before changing the target, check the logging. Cooking oil, drinks, the handful from the bowl and the weekend you did not write down explain this far more often than a slow metabolism. Our FAQ covers how logging works in the app.
If the weekly average genuinely has not moved in three weeks, change one thing: take about 10 % off the target, or add a daily walk, and hold that for three more weeks. Not both at once, and not two cuts in a row.
It is an estimate, and it has limits
An equation cannot see your muscle mass, your medication or your thyroid, so two people with identical inputs can sit a few hundred calories apart. Treat it as a starting point you correct with two or three weeks of your own data, not as a fact about your body. The equation has only two sex variants, so the calculator has two.
This is not health advice, and it is not for everyone: it gives no numbers at all to anyone under 18. If you are pregnant or breastfeeding, have a condition or medication that affects weight or appetite, or have a history of an eating disorder, the right next step is a professional, not a form that sees six fields.
Questions about the numbers
How accurate is this calculator?
It is an estimate, and the honest answer is that it lands close for most people and clearly off for some. The Mifflin-St Jeor equation works from four numbers and cannot see body composition, medication or how restless you are.
The accurate version of your maintenance level is not a formula at all: it is what happens to your weekly average weight when you eat a steady amount for three weeks. Start from the estimate, then let your own data correct it.
Why is my target higher than the goal I picked?
Because the deficit you chose would have taken the result below the floor: your own basal metabolic rate, or 1,500 kcal for men and 1,200 kcal for women, whichever is higher. In that case the calculator raises the number to the floor and says so on the result.
It happens most often to smaller and older bodies at a sedentary activity level, where maintenance is low to begin with. The way out is not a deeper cut but a higher maintenance level: more walking, more sessions, more time on your feet.
Is that much protein really necessary?
Necessary for staying alive, no. Useful if you are training and want the weight you lose to come off fat rather than muscle, yes. The gram figures here (2.0 per kilo while losing, 1.8 while building, 1.6 at maintenance) are ordinary targets for someone lifting weights, not a maximum.
If you are heavily overweight, protein per kilo of current body weight comes out high; using a weight closer to where you are heading is a common and sensible adjustment.
Should I eat back the calories I burn in a workout?
Not on top of this number. The activity factor you picked already contains your training, so adding a workout on top counts it twice. That double count is one of the most common reasons a deficit disappears.
The other reason is that watch and machine estimates of burned calories are generous. If your training changes for good, change the activity level here instead of eating the estimate back.
How often should I redo this?
Every four or five kilos of change, or whenever your normal week changes: a new job, a new training schedule, an injury. Redoing it weekly is pointless, because a few hundred grams moves the result by a handful of calories.
The exception is a long diet. As you get lighter your maintenance level genuinely falls, so a target that worked in month one can be too high by month three.
Can I lose faster than half a kilo a week?
Physically yes, and that is why the calculator stops there. A bigger deficit takes more muscle with it, gets harder to hold week after week, and the weight that comes off fastest is the weight that comes back fastest.
Half a kilo a week is 26 kilos in a year if you actually hold it, which almost nobody does without the boring parts: sleep, protein, strength training and a target you can live with on a Wednesday.
Do you store what I type into this page?
No. The calculation runs in your browser as JavaScript. Your age, height and weight are never sent to a server, never written into the address bar, and never saved on your device: reload the page and they are gone.
The page also loads no third-party scripts, fonts, analytics or embeds, so nobody else sees your visit either.
Is this the same number the Wellboy app gives me?
The app uses the same Mifflin-St Jeor equation and the same five activity levels, so the maintenance estimate matches. It rounds its suggestion differently and lets you type your own numbers over it, so the final targets can differ by a little.
The real difference is what happens next: in the app the target is not a result you read once, it is the line your day is measured against every day.
The number is the easy part
The target above is a one-off calculation and it took you thirty seconds. The part that actually changes something is the daily one: writing down what you ate, watching the three macros fill up, and noticing on Sunday that the week averaged out where you wanted it.
That is what Wellboy is for. You set the same daily target in the app, log food by hand, by barcode or from a photo, and the day view shows how far the day is from your numbers. Training goes into the same app, so the food side and the training side finally add up in one place instead of two.
Have a look around first: the movement library has 408 movements with demo clips and written instructions, the workout library has ready-made sessions, and the recipe library is where the food side starts.
Read the FAQ