What TDEE actually is
TDEE — Total Daily Energy Expenditure — is roughly how many calories you burn in a day, all in: resting metabolism plus everything you do on top of it. It’s an estimate, not a precise number. Two people with the same age, sex, height, and weight can have TDEEs that differ by a few hundred calories.
Why most people overestimate activity level
The single most common mistake when using a TDEE calculator is overestimating activity level. “Moderately active” doesn’t mean you go to the gym sometimes — it means three to five real training sessions a week, on top of a day that isn’t otherwise sedentary. If you sit at a desk all day and lift three times a week, you’re probably closer to “lightly active” than “moderately active.” When in doubt, pick the lower tier.
What to do with the result
The maintenance number is your starting point. If your weight stays roughly flat for two to three weeks while eating that many calories, the estimate is close enough. If you’re gaining or losing, adjust by 100–200 kcal/day and check again.
The cut and bulk targets are exactly that — targets, meaning what you eat, not what you burn. They use modest percentages (−20% for cutting, +10% for bulking) that work for most people. More aggressive deficits exist but tend to backfire below ~1,500 kcal/day for women or ~1,800 for men.
When to recompute
Recompute when your weight changes by roughly 10 lb (5 kg) in either direction, or when you switch goals. TDEE scales with body mass, so the number you got at 200 lb isn’t right at 180 lb anymore.
A note on this calculator
This is general guidance, not medical advice. If you have a condition (thyroid, diabetes, eating-disorder history, pregnancy, post-surgical) or you’re taking medication that affects metabolism or appetite, talk to a qualified professional before changing your intake meaningfully.