What is TDEE and how are daily calories estimated?

TDEE means total daily energy expenditure: the energy your body uses over a full day. It includes resting metabolism, digestion, everyday movement and planned exercise.

Most online estimates use two steps:

1. Estimate resting energy from age, sex, height and weight
2. TDEE = resting estimate x activity factor

If resting energy is 1,380 kcal/day and the selected activity factor is 1.55, the estimated TDEE is about 2,139 kcal/day.

That number is a starting point for maintenance calories, not an exact allowance. Two people with the same inputs can move differently, and the same person’s expenditure changes with steps, training, work, health and body weight. Activity selection is often the largest source of error.

Use the TDEE calculator with a normal week’s activity. Keep intake and routine reasonably consistent for two or three weeks, compare weekly average weight and refine the estimate if the trend differs from your goal.

TDEE can inform maintenance, a modest deficit or a cautious surplus, but it cannot judge diet quality or replace individualized advice.

Sources

• Mifflin et al.: resting energy equation
• National Academies: Dietary Reference Intakes for Energy