Maintenance calories
The daily intake at which your weight stays stable: your expenditure, expressed as food.
Maintenance calories are the intake at which your weight stays stable: your total daily energy expenditure expressed as food. It is the number every diet is defined against, since a deficit and a surplus only mean anything relative to it.
Every calculator estimate of it is a prediction from a population equation, and individual variation around that prediction runs into the hundreds of calories. The equation is a starting point; your own weight trend is the measurement.
Finding it properly takes two or three weeks. Eat consistently, weigh yourself daily under the same conditions, and compare weekly averages. If the average is flat, that intake is maintenance. Daily readings are dominated by water, salt, carbohydrate and the state of your digestive tract, and are close to useless in isolation.
It moves, in both directions and for several reasons. It falls as you lose weight, both because a smaller body costs less and because spontaneous movement declines, and it rises as you gain. It also shifts with training load, illness, sleep and even the temperature of your surroundings.
Understanding it makes the concept of a maintenance phase useful rather than an admission of defeat. Deliberately eating at maintenance for a few weeks between deficits lets appetite, hormones and training performance recover, and it rehearses the skill that actually keeps weight off afterwards.
Total expenditure is also more stable across adult life than folklore suggests. A large study using doubly labelled water found that, once fat free mass is accounted for, expenditure holds steady from roughly age 20 to 60 and only declines after that.
In practice, estimate with our TDEE calculator, verify against three weeks of weekly averages, and re-estimate every few kilograms of change.