Energy · Tool 2 of 5
TDEE and Calorie Target
Your TDEE is an estimate, not a measurement. It is the right place to start and the wrong place to stop — the number that matters is what your weight does over the next two weeks.
Tell me about you
What the equation is doing
This uses the Mifflin-St Jeor equation for basal metabolic rate, then multiplies by an activity factor. BMR is what you would burn lying still all day — for most people somewhere around 60 to 75 per cent of total daily burn, with the thermic effect of food adding roughly 8 to 10 per cent and everything you do that is not sleeping making up the rest.
Why the activity multiplier is the weak link
The BMR part is reasonably reliable. The multiplier is not: the gap between "trains three times a week and sits the rest of the day" and "trains three times a week and walks 12,000 steps" is several hundred calories, and both people pick the same option.
How to find your real number
Eat at the estimate for two weeks. Weigh daily, average weekly, compare week two to week one. Steady means the estimate was close. That result beats any equation, because it came from you.
How the macros are set
Below the target you will find protein, fat and carbohydrate broken out, each set a different way on purpose. Protein comes from your bodyweight and training focus — the same table the protein calculator uses — because requirement tracks the muscle you are trying to keep, not the calories you happen to be eating. Fat is set to a floor of 20% of your target, because hormone production and absorbing vitamins A, D, E and K depend on fat being adequate as a share of intake. Carbohydrate takes whatever calories are left, because it is genuinely the flexible one — the macro that should move with however much room the other two leave behind.
That is different from splitting the whole target into a fixed percentage — 40/30/30 and similar presets — for everyone regardless of body size. Two people eating the same 2,200 calories but weighing 60 and 100 kilograms do not need the same grams of protein, and a straight percentage split hands them exactly that anyway.
Worth being precise about: the size of the fat floor and the shape of the carbohydrate range come from published sports-nutrition guidance. Running protein first, fat second and carbohydrate last — instead of computing all three from a percentage of this target — is FitCalc's own coaching approach, not a rule copied from a textbook. See references for exactly which part is which.
When the numbers do not fit
On an aggressive deficit, or for someone who is both very light and very active, protein and fat floors can add up to more than the calorie target allows. When that happens this calculator trims fat toward a harder floor first, then protein toward the bottom of its range, before it ever shows you a number. If it still does not fit, it says so rather than printing a carbohydrate figure that would not be true.
Questions I get asked
Which equation is this and why?
Mifflin-St Jeor. It is the standard modern choice and performs at least as well as the older Harris-Benedict equation.
Why did my target get raised?
This calculator will not return a target below 1,500 calories for men or 1,200 for women. That is a built-in safety floor, not a number derived for your body — very low intakes make protein and micronutrient needs hard to hit and adherence tends to collapse. If your numbers land there, the fix is a slower rate or more activity, not a lower floor.
Does my metabolism slow down when I diet?
Yes, to a degree, and mostly for reasons that are not mysterious: you weigh less so you burn less, you eat less so the thermic effect of food is smaller, and you move less without noticing.
How often should I recalculate?
Every 4 to 6 kilograms of weight change, or whenever progress stalls for three weeks at consistent intake.
Why not just use a 40/30/30 percentage split?
A percentage split gives two people who eat the same calories the same grams of protein even if one weighs 60 kilograms and the other weighs 100. Protein needs track bodyweight and training, not calories, so this calculator sets protein first from bodyweight, then fills fat and carbohydrate around it. The percentages shown at the end are what comes out, not something you choose going in.
What happens if my numbers do not add up?
On a steep deficit combined with a high protein need, the calculator trims fat toward a hard floor and then protein toward the bottom of its range before it ever shows you a result — and if that still does not leave room for a real carbohydrate number, it tells you the target is too aggressive rather than printing one that is not true. A slower rate of loss almost always fixes it.
Read next
- TDEE Explained: Why the Number Is a Starting Point What total daily energy expenditure is made of, why calculators disagree with each other, and how to find your real number in two weeks.
- Why Your Metabolism "Slows Down" on a Diet Metabolic adaptation is real, mostly explainable, and smaller than the internet claims. Here is what actually changes and which part you can control.
- How Fast Should You Lose Fat? Picking a rate of loss is the decision that determines how much muscle you keep and whether you finish the phase at all.