How many calories do you burn in a day? TDEE explained

2026-10-10 · Zefro

Every calorie target starts with one number: what you burn in a day. It is called TDEE, total daily energy expenditure. You can estimate it in two steps, then let your own food log and scale correct it.

What your daily burn is made of

Your body spends energy in three ways. The first is basal metabolism, the cost of keeping you alive at rest. The second is the energy used to digest and process food. The third is physical activity, which covers your training and everything else you do on your feet.

The food part is the smallest. On a mixed diet it is about 5 to 15 percent of daily energy expenditure, higher when you eat more protein and lower when you eat more fat. The glossary calls it the thermic effect of food.

Activity is the part that differs most between people, and it is not only the gym. In one overfeeding study, 16 volunteers ate 1,000 kcal a day above their needs for 8 weeks. Two-thirds of the rise in their daily burn came from non-exercise activity such as fidgeting, posture and moving around, and differences in it explained a tenfold spread in how much fat they stored.

Step 1: your resting burn

BMR is the calories you burn at complete rest. Zefro uses the Mifflin-St Jeor equation: 10 × weight in kg + 6.25 × height in cm − 5 × age, then +5 for men or −161 for women.

A 30-year-old man, 80 kg and 180 cm: 800 + 1,125 − 150 + 5 = 1,780 kcal.

A 30-year-old woman, 65 kg and 165 cm: 650 + 1,031 − 150 − 161 = 1,370 kcal.

If you do not give a sex, Zefro uses −78, the midpoint between the two constants. The man above would then get 1,697 kcal.

The equation comes from a 1990 study that measured the resting energy expenditure of 498 healthy women and men aged 19 to 78 and fitted a formula to the results. A later systematic review of the common equations found Mifflin-St Jeor the most reliable: it landed within 10 percent of measured resting burn in more people than any other equation. That is the best case, not a promise. For the man above, 10 percent is 178 kcal a day.

Step 2: your activity

Multiply BMR by an activity level: 1.2 for a desk job with no exercise, 1.375 light, 1.55 moderate, 1.725 very active, 1.9 for athletes. At 1.55 the same man burns 1,780 × 1.55 = about 2,759 kcal a day.

This choice moves the result more than any other input. For the same man the levels give 2,136, 2,448, 2,759, 3,071 and 3,382 kcal. Each step is about 300 kcal a day, and the full range is more than 1,200 kcal.

The woman above, at the light level, burns 1,370 × 1.375 = about 1,884 kcal a day.

The activity multiplier already includes your training. Do not add workout calories on top of it, or you count the same exercise twice.

The formula also shows how the number moves. Every kilogram you lose takes 10 kcal off your BMR, and every 10 years of age takes off 50. At 1.55, losing 5 kg lowers the estimate by about 78 kcal a day.

Step 3: from TDEE to a target

Your TDEE is your maintenance calories. Zefro turns a weekly goal into a daily change with a rule of thumb: about 7,700 kcal per kilogram of body weight. To lose 0.5 kg a week, that is 0.5 × 7,700 ÷ 7 = 550 kcal a day, so the man at 2,759 kcal would eat 2,209. To gain 0.25 kg a week, he would eat 275 more, 3,034 kcal.

The rule is a starting point, not a law. An analysis from the US National Institutes of Health found that it roughly fits people with a lot of body fat but overstates the deficit needed per kilogram for leaner people. A later model from the same group showed that body weight responds slowly to a change in intake, with half times of about a year. In practice your results drift from the plan, so the plan needs updating.

Why your real number differs

• Body composition. In the original study, fat-free mass predicted resting burn better than any other single measure. Two people of the same weight can burn different amounts.
• Daily movement. Non-exercise activity varies widely between people, and in the overfeeding study it rose by very different amounts.
• Age. A large study of total expenditure measured with doubly labelled water found that, adjusted for fat-free mass, it stays stable from about 20 to 60 and then declines in older adults. The age term in the equation is a rough average.
• Who the equations were built on. The review noted that older adults and US ethnic minorities were underrepresented in developing and testing these equations.

Common mistakes

• Picking the activity level you want, not the one you live. Base it on a normal week, including your job and your steps, not your best week.
• Trusting your watch's calorie number. A Stanford study tested seven wrist-worn devices against lab measurement, and none estimated energy expenditure with an error below 20 percent. On a 500 kcal reading, 20 percent is 100 kcal.
• Counting exercise twice. If you chose an active level, your training is already in the number.
• Logging only the good days. In a study of people who said they could not lose weight on under 1,200 kcal a day, the group underreported what they ate by an average of 47 percent and overreported their activity by 51 percent. Their energy expenditure was within 5 percent of predicted. The error was in the record, not the metabolism.
• Judging too early. A few weigh-ins are not a trend. Give it at least two weeks.
• Never updating it. Weight and age are both inputs, so recalculate after a real change in weight or routine.

Let your own data correct it

The equation is a guess about an average person who looks like you. Your food log and your scale measure you. If your weight holds steady for weeks while you eat about 2,500 kcal a day, your maintenance is about 2,500, whatever the formula said.

Zefro+ runs this check every week. It takes your average intake on the days you logged food and subtracts the energy your weight trend says you stored, at 7,700 kcal per kilogram. Days you did not log are skipped, not counted as zero. The trend is a straight line fitted through all your weigh-ins, so one missed or odd weigh-in does not break it. The estimate needs at least 10 days of logged food and at least 4 weigh-ins spread over two weeks.

A worked example: you averaged 2,300 kcal on logged days and your trend is falling by 0.3 kg a week. That is 0.3 × 7,700 ÷ 7 = 330 kcal a day coming out of storage, so your burn is about 2,300 + 330 = 2,630 kcal.

When your pace drifts from your goal, the weekly check suggests a new target. Each change is at most 100 kcal a day, and at most 50 for your first one, so your target moves in small steps.

Who this suits, and who it does not

This method suits healthy adults who want a calorie target to lose, keep or gain weight, and who will log food and weigh in for a few weeks. The equation was built on adults aged 19 to 78.

It is a weaker fit the further you are from the people it was built and tested on, and it is not a medical tool. Calorie targets are general guidance. If you are pregnant, breastfeeding or have a history of eating disorders, talk to a doctor first.

What to do with it

• Eat around that number to hold your weight.
• Eat below it to lose fat, above it to gain.
• Treat it as a starting point. Weigh yourself for two weeks and adjust by what actually happens.
• Turn the target into protein, carbs and fat. How to set your macros walks through the split.
• Log honestly, including the weekends, so the number you correct is real.

Questions

Should I eat back the calories from my workout? Not if your activity level already includes your training. That is what the multiplier is for.

Why did my weight loss slow down? A lighter body burns less: in the equation, each kilogram lost takes 10 kcal off BMR. Body weight also responds slowly to a change in intake. Recalculate and check your log before cutting further.

Do I burn less as I get older? The equation takes 5 kcal off BMR for each year. Measured data show expenditure, adjusted for fat-free mass, holding steady from about 20 to 60 and declining after that.

How accurate is a TDEE calculator? For resting burn, the best equation lands within 10 percent for many people, not all. The activity level adds more uncertainty. Your own weight trend is the final word.

What if I do not want to give my sex? Zefro uses the midpoint constant, −78, and tells you it did.

Any equation is an estimate and individuals vary. The TDEE calculator does the sums for you, and the macro calculator turns the result into protein, carbs and fat. Terms like BMR, TDEE and calorie deficit are in the glossary.