FitDexCalorie calculator
How many calories you need in a day isn't a single number. It falls out of three questions: what your body burns doing nothing, how much you move during the day, and where you want to end up — and because all three are separate parts of the same equation, a figure drawn from one of them hangs in the air until you know the others. Fill in the four boxes below. We'll work out all three.
Your daily calorie target
- Basal metabolic rate1,452 kcal
- Protein168 g
- Carbs253 g
- Fat62 g
- Your daily water need2.3 L
Capped at the safety floorYour figure fell below this value; we don't show targets under 1,200 kcal for women or 1,500 kcal for men. Intakes that low aren't something to attempt without professional supervision.
Start tracking this goalThis number comes from the very same formula the FitDex app uses. Install the app and you won't be handed a different target.
How is it calculated?
First we work out your basal metabolic rate: the energy your body spends lying still, purely to keep your heart beating, your lungs working and your temperature up. The equation is Mifflin-St Jeor — for men, 10 × weight + 6.25 × height − 5 × age + 5; for women the same sum ends in −161 instead of +5.
That figure is then multiplied by an activity factor: 1.2 if you're sedentary, 1.375 lightly active, 1.55 moderately active, 1.725 very active, 1.9 extremely active. The result is your total daily energy expenditure — what you'd eat to stay exactly where you are.
The last step is your goal. Losing takes 400 calories off, gaining puts 400 on. A harsher deficit like 500 or 1,000 is deliberately avoided: going faster than half a kilo a week raises both muscle loss and the odds of quitting. If the result drops below 1,200 calories for women or 1,500 for men, we stop there.
Macros are then split out of that target: 30% of the calories as protein, 45% as carbohydrate, 25% as fat. Protein and carbs carry 4 calories per gram and fat carries 9, which is why the gram figures come out so differently.
How to read your result
This is an estimate, not a measurement. Two people of the same height and weight can differ by as much as 10% in what they actually burn, depending on muscle mass, hormones and how well they sleep.
Here's how to use it properly: hold the target for two weeks and weigh yourself once a week, at the same time of day, under the same conditions. If the scale isn't moving the way you expected, shift the target by 100–150 calories, because the formula can only hand you a starting point and the real tuning comes out of what the scale records across those two weeks.
Don't go below your basal metabolic rate. That number isn't negotiable padding. It's the bill your body pays even while idling, and staying under it slows your metabolism and increases how much of the lost weight comes from muscle.
Frequently asked questions
Why does another site give me a different number?
Most sites use the Harris-Benedict equation. It rests on data from 1919 and systematically overstates today's needs. We use Mifflin-St Jeor because it lands closer to resting energy measured in a lab. The gap is usually somewhere between 100 and 200 calories. The activity multiplier matters too: some sites offer three levels instead of five, so your real level gets rounded to the nearest one they have.
Which activity level should I pick?
Think about your DAY, not your workouts. Someone who trains three times a week and spends the rest of the time at a desk is usually "lightly active", not "moderately active" — an hour of training doesn't offset ten hours of sitting still. If you're under about 8,000 steps a day, going one level down is almost always the better call. When in doubt, pick the lower one: an overestimated target leaves you hunting for months for the reason the weight won't move.
Why subtract 400 calories to lose weight and not 500?
A 500-calorie deficit works out to roughly half a kilo a week, and there's nothing wrong with it in itself. But staying at 400 has two concrete reasons: the bigger the deficit, the larger the share of muscle inside the weight you lose; and the harsher the restriction, the higher the drop-out rate. A small deficit you keep for six weeks takes off more than a big one you abandon after two.
Is this the same calculation as in the FitDex app?
Yes — same equation, same multipliers, same safety limits. What the app adds is this: the number doesn't just sit there on screen, it becomes your daily target with one tap. From then on you log meals by photographing them and watch how much of the target you've filled as the day goes. The calculation here is the start; the tracking in the app is what follows.
Related tools
- BMR calculatorWork out the energy your body spends doing nothing, using the Mifflin-St Jeor equation. Your total daily expenditure and water need come with it. The equation is written out in full — along with which part of it you can actually change.
- BMI calculatorEnter your height and weight to see your body mass index, which category it falls in and the healthy weight range for your height. A body fat estimate comes with it — it says what BMI alone cannot.
- Macro calculatorTurn your daily calorie target into grams of protein, carbohydrate and fat. We publish the ratio we use and why we chose it, instead of offering preset templates with no explanation.
- Water intake calculatorWork out your daily water need from your weight. We also trace where the "eight glasses a day" rule came from and why it's been misread — the real indicator isn't a glass count, it's the colour of your urine.
This tool is for information only and is not a substitute for medical diagnosis or treatment. Talk to a healthcare professional before making a lasting change to how you eat.