What your TDEE number means
TDEE, or total daily energy expenditure, is the total number of calories your body uses in a day. Most of it goes to keeping you alive at rest: breathing, circulation, and keeping your organs running. The rest covers digesting food and every bit of movement, from walking to the car to a workout.
If you eat about as many calories as your TDEE, your weight tends to stay where it is. Eat less, and your body makes up the gap from stored energy, mostly fat. That gap is what the weight loss targets above are built on.
How this calculator works
The calculator first estimates your basal metabolic rate (BMR) with the Mifflin-St Jeor equation, published in 1990:
- Men: 10 × weight in kg + 6.25 × height in cm − 5 × age + 5
- Women: 10 × weight in kg + 6.25 × height in cm − 5 × age − 161
A systematic review comparing the common equations found Mifflin-St Jeor was the most reliable for healthy adults, both with and without obesity. If you enter a measured body fat percentage, the calculator uses the Katch-McArdle equation instead, which works from lean body mass: 370 + 21.6 × lean mass in kg.
Your BMR is then multiplied by an activity factor, from 1.2 for a sedentary day to 1.9 for a physical job plus daily training. The result is your TDEE.
Using your number to lose weight
The targets subtract 250 or 500 calories a day from your TDEE. Those figures come from the old rule of thumb that a pound of fat holds about 3,500 calories, so a 500 calorie daily gap adds up to about a pound a week.
In practice, loss usually slows over time. As you get lighter, your body burns fewer calories, so the same intake creates a smaller gap. Researchers at the National Institutes of Health built a more detailed model of this, and it shows the 3,500 calorie rule overestimates long-term loss. The practical answer is to recalculate after every 10 pounds or so and to judge progress by your weight trend over several weeks rather than any single day.
Why your real number may differ
An equation can only use what it knows about you. Muscle mass, genetics, sleep, some medications and medical conditions such as hypothyroidism all shift how many calories you burn. Activity is the hardest part to estimate, and most people pick a level that is too high.
The most accurate TDEE is the one you measure yourself. Eat at your maintenance target for two to three weeks and weigh yourself under the same conditions each morning. If the weekly average holds steady, the estimate is right for you. If it drifts, adjust by 100 to 200 calories and repeat.
Questions people ask
What does TDEE mean?
TDEE stands for total daily energy expenditure: the number of calories your body uses in a full day, including your resting metabolism, digestion and all movement. Eating about your TDEE keeps your weight roughly stable.
How accurate is a TDEE calculator?
It is an estimate. The Mifflin-St Jeor equation predicts resting metabolism within about 10% of a lab measurement for most healthy adults, but some people fall outside that range. Treat your result as a starting point and adjust after two to three weeks of tracking your weight.
How many calories should I eat to lose weight?
A common starting point is 250 to 500 calories below your TDEE, which this calculator shows as the 0.5 lb and 1 lb a week targets. Weight loss tends to slow over time as your body gets smaller, so the weekly rate is a rough guide rather than a promise.
Should I enter my body fat percentage?
Only if you have a reasonably reliable number, for example from a DEXA scan. With body fat entered, the calculator switches to the Katch-McArdle equation, which uses lean mass. A rough guess can make the result less accurate, not more.
Which activity level should I choose?
Most people overestimate. If you work at a desk and exercise a few times a week, Lightly active or Moderately active is usually closer than Very active. If your weight changes faster or slower than expected, move one level up or down.
What is the difference between BMR and TDEE?
BMR (basal metabolic rate) is what your body burns at complete rest. TDEE is your BMR multiplied by an activity factor, so it also covers daily movement and exercise. TDEE is the number to plan meals around.
Sources
- Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition. 1990;51(2):241–247.
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association. 2005;105(5):775–789.
- Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. The Lancet. 2011;378(9793):826–837.
- National Institute of Diabetes and Digestive and Kidney Diseases. Body Weight Planner.