Calorie Intake Calculator: What You Burn, What to Eat
This calorie intake calculator estimates how much energy your body spends in a day and turns that number into a daily target to lose, maintain or gain weight.
Weight, height, age and routine. The rest is arithmetic.
Where the number comes from
It starts with your basal metabolic rate, what the body spends at rest. That gets multiplied by how much you move. What comes out is the whole day.
The equation, spelled out
Mifflin-St Jeor works like this: 10 times weight in kilograms, plus 6.25 times height in centimetres, minus 5 times age, plus 5 for men or minus 161 for women. That result is your basal metabolic rate. It is then multiplied by an activity factor ranging from 1.2, for someone who sits all day, up to 1.9, for someone training hard almost every day. The equation was published in the American Journal of Clinical Nutrition in 1990 and still has the smallest error in healthy adults, typically within 10% either way. That is why it replaced Harris-Benedict in most clinics, and it is the equation running behind this calorie intake calculator.
How to pick your activity level without guessing wrong
This is where most calculations go sideways, because the activity factor can swing the result by several hundred calories. Sedentary means a desk job and no training, even if you walk to the bus stop. Light covers 1 to 3 exercise sessions a week. Moderate is 3 to 5 consistent sessions. Hard means 6 or 7, and very hard applies only to people training twice a day or doing heavy manual labour. When torn between two levels, pick the lower one. Overestimating your burn is the most common mistake and the most expensive: you believe you have 300 kcal of room that does not exist, you eat into that imaginary room, and the scale sits still. After three weeks of logged weights, the scale itself corrects the guess better than any table.
If you want the resting side of the equation before you look at the target, the guide on basal metabolic rate takes that part slowly.
How to read your result
Three targets come out of the same calorie intake calculator. You pick one.
| Goal | Adjustment | Expected pace |
|---|---|---|
| Lose fat | 500 kcal below burn | about 0.5 kg per week |
| Maintain weight | the full burn | a steady scale |
| Build muscle | 300 kcal above burn | 0.25 to 0.5 kg per week |
Why there is a calorie floor
Cutting deeper does not speed anything up in a way you can sustain. Below 1,200 kcal for women and 1,500 kcal for men it becomes hard to hit protein, iron and calcium in a day, and hunger climbs to the point of ending the diet during the first bad week. That is why the calculator respects the floor even when the arithmetic would ask for less. Anyone with a lot of weight to lose who wants a steeper cut should do it with supervision rather than alone. The piece on how many calories to lose weight covers how to size the cut without overdoing it.
How long before the scale answers
The first week misleads in both directions. Cut carbohydrates and 1 or 2 kilos come off almost immediately, nearly all of it water bound to glycogen. Start lifting and you may see nothing at all, because muscle holds fluid while it adapts. The signal that matters shows up between week three and week four, when the weekly average starts trending down consistently. Weigh at the same time each day, preferably in the morning, and read the seven day average instead of any single number. If three weeks pass with no change while eating the calculated target, there are two likely explanations, and a broken metabolism is not one of them: either the activity level was overestimated, or the real portion is bigger than the logged one.
You get the number here. If you want to understand why the cut works and how to hold it, the guide on calorie deficit explains the whole mechanism.
The maths is fine. The plate lies.
A study in the New England Journal of Medicine measured people who were certain they ate very little. They underreported their own intake by nearly half.
The calorie intake calculator does not fail because of the equation. It fails because the portion you picture is not the portion on the plate.
The conversion table for tablespoons to grams shows how wide that gap gets between the spoon you use and the actual weight.
See my plate in calories →Who this number is for
Works well for
- Healthy adults between 18 and 65
- Anyone who needs a starting point
- People training who want to adjust intake
- Anyone regaining weight without knowing why
Not for
- Pregnant and breastfeeding women
- Children and growing teenagers
- Elite athletes
- Anyone treating thyroid, kidney or eating disorders
In those cases the number has to come from a clinician, not a general equation.
What the calorie intake calculator does not do
It gives you the ceiling for the day. It has no idea what went underneath it.
The three things left out
First, it does not measure what you ate, only what you could eat. Second, it does not split the number into protein, carbohydrate and fat, and that split changes how hungry you feel on identical calories. Third, it does not update itself: as weight drops, burn drops with it, so the calculation needs redoing every 4 or 5 kilos lost. None of that makes the number useless. It just means the number is the start of the process, not the process.
To close the day against your target without typing food after food, the route is an AI calorie counter.
Your number is ready. What about tomorrow?
The calorie intake calculator solves day one. The app solves the other thirty.
Try It Free →No card to start. Cancel any time.