Maintenance Calories: How to Find Yours From Your Own Log

Every calorie calculator gives you a maintenance number, and every one of them is an estimate built from your age, height, weight and a guess at how active you are. That guess is where most of the error lives.

There is a second way, and it needs nothing but what you are already recording. If you log what you eat and you weigh yourself regularly, your own data can tell you how many calories keep your weight steady. It takes about four weeks and a little arithmetic, which this post spells out.

Two ways to get a maintenance number

The estimate. Your basal metabolic rate comes from a formula such as Mifflin-St Jeor, from a 1990 study of resting energy expenditure. You multiply it by an activity factor to get your TDEE, total daily energy expenditure. Our TDEE calculator and the BMR calculator do this, and what is TDEE explains the method. It is quick, and it is only as good as the activity level you pick.

The measurement. Over a few weeks, the energy you eat minus the energy you store tells you what you burned. If you ate 1,850 calories a day on average and lost weight, you burned more than 1,850. How much more depends on how much weight you lost. That is the method here.

The formula

Over a window of days:

Maintenance = average daily intake - (weight change in kg x 7,700 / days)

The 7,700 is the energy value we assign to a kilogram of body weight (about 3,500 kcal per pound), the same rule of thumb used throughout CalorTracker. If you lost weight, the weight change is negative and maintenance comes out above your intake. If you gained, it comes out below.

Dividing 7,700 by 28 days gives 275. So over a four-week window, every kilogram of change moves the answer by 275 calories a day. A loss of 0.8 kg means you were eating about 220 calories a day below maintenance.

Worked example

Take a 34-year-old woman, 168 cm, who logs her food and weighs herself for four weeks.

1. Average intake. Over 28 days her logs average 1,850 kcal a day.
2. Weight trend. Her average weight in the first week is 68.0 kg; in the last week it is 67.2 kg. The change is -0.8 kg.
3. Energy gap. -0.8 x 7,700 / 28 = -220 kcal a day.
4. Maintenance. 1,850 - (-220) = about 2,070 kcal.

Now compare it with the estimate. Using her average weight in the window (67.6 kg), the Mifflin-St Jeor formula gives a BMR of 10 x 67.6 + 6.25 x 168 - 5 x 34 - 161 = 1,395 kcal. The activity multipliers in our calculator then give:

Her measured 2,070 falls between "lightly active" (1,918) and "moderately active" (2,162). That is a typical result: the estimate was close, and the log told her which side of it she lives on. It also shows how wide the gap between adjacent activity levels is, at more than 200 calories a day, which is the reason a measured number is worth having.

A gain works the same way. Someone who averaged 2,300 kcal and gained 0.4 kg over 28 days has stored 0.4 x 7,700 / 28 = 110 kcal a day, so maintenance is 2,300 - 110 = about 2,190 kcal.

Why the window matters

The formula is only as good as the two weights in it, and a scale reading moves for reasons that have nothing to do with fat: water, salt, a heavy meal, the time of day. Averaging a week at each end smooths that out, but it does not remove it. Suppose your trend weight is off by 0.5 kg at one end. The error that creates in your daily answer depends on how long the window is:

(0.5 x 7,700 divided by the number of days.) A two-week window can be out by more than an entire snack; six weeks gets the noise down to the size of a spoon of oil. Four weeks is a sensible compromise, and longer is better if your weight has been steady. The post on weight tracking that shows if it is working covers how to read a trend instead of single weigh-ins.

What can make the answer wrong

• Missing food. The result assumes the log is complete. If you leave out a snack, a drink or the oil in the pan, your intake is understated and so is your maintenance. Logging by photo helps because it takes seconds. Our post on how accurate AI calorie counting is explains what to expect from estimates.
• Too few logged days. Average only days you logged completely. A day with one meal recorded is not a 600 kcal day, it is a day to leave out.
• A moving target. If you changed your diet or training halfway through, the average describes neither half. Start a fresh window when something changes.
• Water shifts. A week of unusual salt, a new training block or a change in carbohydrate intake can move the scale by a kilogram without any change in fat. If a window ends on one of those weeks, extend it.
• The rule of thumb itself. 7,700 kcal per kg is an approximation, and the body adapts as weight changes. Hall and colleagues modelled this in 2011, and it is why the rule is better over a few weeks than over many months. Our note on the calorie deficit says the same.

If your logged days are patchy, treat the result as a range, not a point. "About 2,000 to 2,150" is a usable answer.

What to do with the number

Once you have it, you have a baseline that belongs to you. A few uses:

• Set a deficit from it. Start from your measured maintenance and take off a percentage, as in how many calories to eat to lose weight, instead of from a formula's guess.
• Check a plateau. If the scale has stalled, recompute over the last four weeks before changing anything. Overcoming diet plateaus walks through what to look at.
• Hold your weight. If maintaining is the goal, eating at your measured number is the plan. Your average, not each day, is what counts.

Re-measure when your weight, job or training changes. A number from last spring does not describe this winter.

A simple routine

1. Log everything, every day, for four weeks. Do not change your habits to make the numbers look good.
2. Weigh yourself at least three times a week, ideally the same time of day, and note the average of the first week and of the last.
3. Average your daily calories over the days you logged completely.
4. Apply the formula, then compare with the TDEE calculator. If they are within a couple of hundred calories, you are in good shape; use the measured one.

Common questions

Is this more accurate than a calculator?

It can be, because it measures your real intake and your real weight change rather than assuming an activity level. It is also easy to get wrong if the log is incomplete, so check both against each other.

Do I need to eat the same every day?

No. The average over the window is what matters. A high Saturday and a low Monday cancel out.

Can I use it while dieting?

Yes, and that is a common case: if you are losing weight at a steady pace on a known average intake, the formula still gives your maintenance. The worked example above is exactly that.

What if my weight did not change?

Then your average intake over the window is your maintenance. The formula's correction term is zero.

Does it work for gaining weight too?

Yes, as in the second example above. A gain means you ate above maintenance, so the correction is subtracted.