TDEE Calculator — Total Daily Energy Expenditure

TDEE stands for total daily energy expenditure: the total amount of energy your body uses across a normal day. It is not just workout calories. It starts with basal or resting metabolism, then adds non-exercise movement, formal exercise, and the thermic effect of food. The National Academies describe total energy expenditure as resting metabolic rate, the thermic effect of food, and physical activity energy expenditure; the Dietary Reference Intakes for Energy chapter is a useful background source for those components.

BMR is usually the largest part of the picture. Depending on body size and activity, resting metabolism often accounts for roughly 45-70% of daily expenditure. The rest is more variable. Food digestion commonly adds around 10% of daily energy use, while physical activity includes both planned exercise and NEAT: walking, standing, chores, posture, and small movements. Endotext's review of non-exercise activity thermogenesis is a good explanation of why two people with similar workouts can still have very different daily burn.

Most online TDEE tools begin by estimating BMR. This page uses Mifflin-St Jeor when body fat is unknown because it performs well as a general-purpose resting energy equation. A systematic review comparing common equations found Mifflin-St Jeor to be one of the most reliable options for nonobese and obese adults; see the PubMed record for the Frankenfield, Roth-Yousey, and Compher review. The original Mifflin-St Jeor equation is indexed under PMID 2305711, and the NIH/NCI also lists it in its REE and physical activity level reference.

If you enter body fat percentage, the calculator switches to Katch-McArdle. The reason is simple: lean tissue drives a large share of resting energy use, while fat mass contributes less. This can make lean-mass-based estimates more useful for people whose scale weight does not describe body composition very well. The tradeoff is measurement quality. A guessed body fat percentage can make the result less reliable, so leave it blank unless you have a number from a reasonably consistent method.

Harris-Benedict still matters historically, and many calculators expose it as a user choice. This page does not ask beginners to choose formulas up front because that creates decision friction before the result means anything. Instead, it uses an automatic default and shows the formula in a collapsed panel. If you want the history, Roza and Shizgal's reevaluation of the Harris-Benedict equation is a common reference point.

TDEE is always an estimate. Activity multipliers compress a messy life into one number. They cannot know how much you fidget, how hard your training sessions really are, how much you walk outside the gym, or whether your weekend looks completely different from your weekday. Most people also overestimate activity level. If you are unsure between two options, choose the lower one and let two or three weeks of scale trend and food tracking tell you whether the estimate needs to move.

For fat loss, TDEE becomes useful because it gives you a baseline before you choose a deficit. Eating about 500 kcal below TDEE is a common starting point. Larger deficits can work, but staying more than 1000 kcal below TDEE is aggressive and usually not a good default without professional supervision, especially if it pushes calories below basic minimums. Protein intake, resistance training, sleep, and consistency matter because the goal is not just to lose scale weight; it is to lose fat while keeping as much lean mass and daily function as possible.

TDEE also changes. As body weight drops, a smaller body costs less energy to move and maintain. During long dieting phases, adaptive thermogenesis can reduce expenditure beyond what body-size change alone predicts. That is one reason a target that worked in month one may stop working in month three. Recheck your TDEE after losing or gaining meaningful weight, and use the number as a living baseline rather than a permanent label.