What the numbers mean, and where they come from
Every calorie target starts from the same two questions: how much energy does your body use just staying alive, and how much more does it use doing everything else? Answer both and you have your maintenance level — the number every other goal is set relative to.
Your Basal Metabolic Rate is the energy your body burns at complete rest: breathing, circulating blood, maintaining temperature, repairing tissue. It is the largest single component of most people's daily burn, typically around 60–70% of the total, and it is not something you consciously control.
Our calculator uses the Mifflin-St Jeor equation, which is generally regarded as the most accurate of the widely used BMR formulas for the general population:
Men: (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
Women: (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
Notice what the equation needs: weight, height, age and sex. All four genuinely change the answer, which is why a calculator that omits any of them is guessing. Height matters because a taller body has more tissue to maintain; age matters because resting metabolism declines gradually over adulthood.
BMR is then multiplied by an activity factor to give TDEE — Total Daily Energy Expenditure — your actual maintenance calories:
| Level | Multiplier | Roughly means |
|---|---|---|
| Sedentary | 1.2 | Desk job, little deliberate exercise |
| Light | 1.375 | Light exercise 1–3 days a week |
| Moderate | 1.55 | Exercise 3–5 days a week |
| Active | 1.725 | Hard exercise 6–7 days a week |
| Very active | 1.9 | Physical job or twice-daily training |
This step is where most of the error creeps in. The multipliers are broad bands, and people reliably overestimate their own activity — a few gym sessions a week alongside a desk job is usually "light," not "active." If your results consistently miss, the activity level is the first input to revisit, not the formula.
Once you know maintenance, a goal is just an adjustment:
It treats weight loss as linear, and it is not. As you lose weight your BMR falls — a smaller body costs less to run — so the same intake that produced a deficit in month one produces a smaller one by month four. This is the ordinary reason for a plateau, and the fix is usually to recalculate at your current weight rather than to cut harder.
Treat the output as a well-informed starting point, not a measurement. Even the best formula estimates BMR within roughly 10% for most people, and further off for those at the extremes of body composition — a very muscular person's needs are typically underestimated, since the equation cannot distinguish muscle from fat.
The practical approach is to use the number as a hypothesis: eat at it consistently for two to three weeks, track what actually happens to your weight, and adjust from the observed result. Your own trend line beats any equation.
The calculator applies everything on this page to your height, weight, age and activity level.
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