What are your true
maintenance calories?

How do I find my real TDEE?

Track your average daily intake for one to two weeks while you weigh yourself consistently, then compare your weight change to what you ate. If you lost weight you were in a deficit, so your true maintenance is higher than your intake; if you gained, it is lower. This calculator does that arithmetic for you using the energy-balance approximation (3500 kcal per pound, 7700 per kilogram). It is the most accurate method because it uses your actual body's response instead of a population average.

Why is my calculated TDEE wrong?

Formula-based estimates like Mifflin-St Jeor or Harris-Benedict are regression equations fitted to large populations. They predict the average person of your height, weight, age and sex — but real individuals routinely land 10–15% above or below that average because of differences in muscle mass, NEAT (fidgeting and spontaneous movement), thyroid function, digestion and activity tracking error. A static formula can never see those differences. Measuring your own weight trend against your own intake does.

How long should I track?

A minimum of 7 days, but 14 is better. Body weight bounces day to day from water, sodium, carbohydrate stores and gut contents — swings that can easily exceed a pound and hide your real trend. Averaging over a full one to two weeks lets that noise cancel out so the underlying signal (true energy balance) shows through. The longer and more consistent your window, the more accurate the result.

Does water weight matter?

Day to day, yes — water is the single biggest source of noise in scale weight, which is exactly why you should use a multi-day average rather than two single readings. Weigh yourself under the same conditions each time (first thing in the morning, after the bathroom, before eating or drinking) and let a 1–2 week window smooth out the daily swings. Over that span, genuine fat or muscle change dominates and water noise largely averages to zero.

Is the 3500 kcal per pound rule exact?

No — it is an approximation. It assumes the weight you lose or gain is roughly the energy density of body tissue, but early in a diet a chunk of change is water and glycogen rather than fat, and metabolic adaptation can shift expenditure over longer periods. That is why this is best used as a rolling estimate that you re-check every week or two, not a one-and-done number. Zenith's adaptive engine does exactly this continuously.