What are maintenance calories?

For practical purposes, yes. TDEE is the calculated estimate of what you burn in a day; maintenance calories are what you have to eat to match it. They describe the same quantity from opposite sides, which is why the TDEE Calculator is the right tool for the question.

The distinction that does matter is between the estimate and the fact. Your TDEE estimate comes from an equation. Your maintenance level is something your body demonstrates over a few weeks. When those two disagree, the body is right.

Two steps, and the calculator does both:

1. Estimate resting metabolism with the Mifflin-St Jeor equation, from your height, weight, age and sex.
2. Multiply by an activity factor between 1.2 and 1.9 to cover the rest of the day.

For a 32-year-old man of 175 cm and 70 kg who is moderately active, that gives a BMR of 1,639 kcal and a maintenance estimate of 2,540 kcal. The second number is the one to eat to.

The accuracy of this rests almost entirely on step two. If you are unsure which factor describes you, it is worth reading how to choose an activity level before trusting the output.

Measure it. The procedure is unglamorous and it works:

1. Eat close to your estimated figure every day for two to three weeks.
2. Weigh yourself under the same conditions: same time of day, after waking, before eating.
3. Compare the average of the first week against the average of the last, rather than reading any single day.

If the average held steady, that intake is your maintenance level. If it drifted down, your maintenance is higher than what you ate; if it drifted up, lower. Adjust by 100–200 kcal and repeat. Two or three cycles of this will get you closer than any calculator can, because it measures the person rather than predicting the population.

No, and this catches people out. Maintenance calories track your body and your routine, so they move when either does. Losing weight lowers them, because there is less of you to run and less mass to carry around. Gaining muscle raises them slightly. A change of job, a change of season, an injury, or simply walking less in winter all shift the figure without any decision on your part.

This is the main reason weight loss stalls after a couple of months. A deficit set against your starting maintenance is a smaller deficit against your current one, because the target moved. Recalculating every 5–10 kg of change keeps the deficit the size you actually intended.

Then recalculate first. The maintenance figure you started your diet with is not the one you finish with, because you are lighter. Returning to your old intake after losing weight is a return to a surplus, not to maintenance, which is exactly how the weight comes back on while the arithmetic looks like it should not.

Re-run the calculator at your new weight, treat the result as a fresh hypothesis, and confirm it against the scale over a few weeks the same way you did the first time.