Chapter 01 · The basics
What TDEE actually measures
Total daily energy expenditure is the number of calories your body uses in a day. It starts with your basal metabolic rate, the energy you would burn at complete rest, then adds the calories you spend digesting food and moving around. This calculator uses the Mifflin-St Jeor equation, which a 2005 systematic review found to be the most accurate of the common predictive equations for resting energy in healthy adults.2
Your basal metabolic rate is multiplied by an activity factor (from 1.2 for sedentary to 1.9 for extra active) to estimate maintenance calories. Eating roughly at maintenance holds your weight steady; a modest daily deficit tends to lower it over time. A deficit of about 500 calories a day is a common starting point for losing close to a pound a week, though the real rate varies from person to person.
| Goal | Rough daily target | What to expect |
|---|---|---|
| Maintain | TDEE | Weight stays about the same |
| Gentle loss | TDEE minus about 500 | Around 1 lb a week for many people |
| Gentle gain | TDEE plus about 250 | Slow gain, often used for muscle |
Targets are starting points, not prescriptions. A clinician or dietitian can personalize them.
Chapter 02 · The fine print
Where the estimate falls short
Predictive equations work from height, weight, age, and sex, so they cannot see your body composition, your medications, your thyroid, or your sleep, all of which affect how many calories you burn. Two people with the same numbers can have meaningfully different needs. Treat the result as a planning anchor and adjust based on what actually happens to your weight over a few weeks.
If you are using a GLP-1 medication or have a medical condition, talk with your care team before setting a calorie target. The right number depends on your history, not just the math. Individual results vary.
