What TDEE means and why it matters
Total daily energy expenditure, usually shortened to TDEE, is an estimate of all the energy your body uses in a day. It is often called your maintenance calories, because eating roughly that amount is, on average, associated with a steady body weight. TDEE is the number that most calorie plans start from: before anyone can talk about eating less or more than they need, they need an estimate of what they need.
This calculator does that in two steps. It first estimates your resting energy, the calories your body uses at rest, with a named formula. It then multiplies that figure by an activity factor to account for movement and exercise. If you already know your maintenance number, for example from careful tracking over several weeks, you can type it in and skip the estimate. Either way you can then compare maintenance with a daily amount you choose yourself.
It is an estimate. Two people with the same height, weight, age and sex can differ by several hundred calories a day in what they actually use. Treat the output as a starting point to be checked against real-world results, not as a prescription.
The four parts of daily energy use
Total energy expenditure is usually described as the sum of four components:
- Resting energy expenditure. The energy used to keep you alive at rest: breathing, circulation, temperature control and cell repair. For most people this is the largest share, often well over half of the total.
- Thermic effect of food. The energy used to digest, absorb and store what you eat. It is commonly put at around a tenth of intake and differs by food type, with protein costing more to process than fat.
- Exercise activity. Planned exercise such as running, lifting or cycling.
- Everyday movement. Walking around, standing, fidgeting, housework and other unplanned movement, which varies a great deal between people.
The calculator does not measure these separately. The first is estimated by the resting formula, and the other three are folded into the single activity multiplier. That is why the activity choice matters so much and why it is the easiest input to get wrong.
The formulas behind the estimate
Mifflin-St Jeor (default)
Published in 1990 from measurements on healthy adults, Mifflin-St Jeor is the default here. For men, resting energy in kcal per day is 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5. For women the final constant is −161 instead of +5. For the example of a 30-year-old man, 175 cm and 75 kg, that is 750 + 1,093.75 − 150 + 5 = 1,698.75 kcal per day.
Revised Harris-Benedict
The original Harris-Benedict equations date from 1919 and were revised in 1984 by Roza and Shizgal. The revised version for men is 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age. For the same example man it gives 1,762.65 kcal per day, a little different from Mifflin-St Jeor. Differences of this size between formulas are normal and a fair picture of the uncertainty.
Katch-McArdle
Katch-McArdle uses lean body mass instead of total weight: resting energy = 370 + 21.6 × lean mass in kg. It needs a body-fat percentage, which you must supply yourself, because the calculator never guesses one. With 20 percent body fat, the example man has 60 kg of lean mass and a resting estimate of 1,666.00 kcal per day. If you do not know your body fat with reasonable accuracy, one of the other two formulas is the safer choice. The body fat calculator and the lean body mass calculator explain how rough those estimates can be.
Choosing an activity level
The activity multipliers are conventional factors, not measurements. They are widely used because they are simple, but they are blunt, and most people overestimate how active they are. The factors used here are:
- Sedentary (×1.2). Little or no exercise.
- Light (×1.375). Exercise 1–3 times/week.
- Moderate (×1.465). Exercise 4–5 times/week.
- Active (×1.55). Daily exercise or intense exercise 3–4 times/week.
- Very active (×1.725). Intense exercise 6–7 times/week.
- Extra active (×1.9). Very intense exercise daily or a physical job.
For the example man, the same resting estimate of 1,699 kcal gives maintenance values from 2,039 kcal at the sedentary level to 3,228 kcal at the highest level. That is a gap of several hundred calories from one dropdown, which is why it is worth being honest about a typical week rather than your best week. A desk job with a few workouts is closer to light than to very active, and the results table on the calculator shows every level side by side.
Worked examples
Maintenance only. The 30-year-old man at 175 cm and 75 kg has resting energy of 1,698.75 kcal. At the sedentary factor of 1.2, maintenance is 2,038.50 kcal per day, or 8,529 kJ. A kilocalorie is 4.184 kilojoules, which is why the calculator shows both units.
A woman with a light activity level. A 35-year-old woman at 165 cm and 65 kg with a light activity level has a Mifflin-St Jeor resting estimate of 1,345.25 kcal and maintenance of 1,849.72 kcal per day.
Comparing a lower amount. If the first example chooses an amount 10 percent below maintenance, the arithmetic is 2,038.50 × 0.90 = 1,834.65 kcal per day, a difference of 203.85 kcal. Choosing a fixed 250 kcal below maintenance instead gives 1,788.50 kcal per day. Choosing 5 percent above maintenance gives 2,140.43 kcal per day.
Those figures show what a chosen number works out to, nothing more. They are not predictions of how your weight will change.
What this calculator does not do
It does not forecast weight loss or gain, set a target date, or tell you a number that is safe or recommended for you. Body weight responds to calories in complicated ways: metabolism adapts, water weight moves, and tracking errors are large. A rule of thumb such as a fixed number of calories per pound of body weight is a rough population average, and it works less well for an individual over many weeks. If you want a plan with a weight goal, speak to a registered dietitian or doctor who can account for your health, medicines and history.
It is for adults aged 19 to 80. It is not suitable during pregnancy or breastfeeding, for children and teenagers, for people with a medical condition that changes energy needs, or for anyone with a history of disordered eating. If any of those apply, please get individual advice rather than relying on a general estimate.
Turning the number into a plan
Once you have a maintenance estimate, the practical step is to compare it with what you actually eat and how your weight behaves over several weeks. If your weight is steady while eating about the estimate, it is a good working number. If not, adjust it by a modest amount and watch again. When you want to split a daily total into protein, carbohydrate and fat, the macro calculator does that, the protein calculator compares reference protein amounts, and the BMR calculator compares all three resting formulas side by side. To see what a workout adds, use the calories burned calculator. The BMI calculator and the wider fitness and health calculators cover related checks.
Food energy in plain numbers
Food energy is usually estimated with the Atwater factors: about 4 kcal per gram of carbohydrate, 4 kcal per gram of protein and 9 kcal per gram of fat, with alcohol around 7 kcal per gram. Those are averages. The real energy your body gets depends on how food is processed and digested, which is why labels and tracking apps are themselves estimates. The macro calculator uses these factors to turn a calorie total into grams of each nutrient.
Calories and kilojoules are two units for the same thing. One kilocalorie is 4.184 kilojoules, so a maintenance figure of 2,039 kcal equals 8,529 kJ. In everyday speech, "calories" almost always means kilocalories.
How to check your estimate against real life
A formula gives you a first guess. The way to improve it is to compare it with what actually happens. A simple approach is to eat at roughly your estimated maintenance for two to four weeks while keeping other habits steady, and weigh yourself at the same time of day. Day-to-day changes of a kilogram or more are normal because of water, salt and food in the gut, so look at the average of a week rather than any single reading. If your weekly average is steady, your estimate is a good working number. If it keeps drifting in one direction, your real maintenance is probably higher or lower than the estimate, and a modest adjustment is the sensible next step.
Common mistakes when estimating calorie needs
- Overstating activity. Choosing a higher activity level than a typical week supports is the most common error and can add several hundred calories to the estimate.
- Counting exercise twice. The activity factor already includes planned exercise, so adding the calories shown by a fitness tracker on top double counts it.
- Trusting a single number. Different formulas disagree by tens to hundreds of calories. The spread is the honest answer.
- Ignoring tracking error. Food labels, portion sizes and restaurant meals are all approximate, and small daily errors add up over a week.
- Forgetting that needs change. Energy needs shift with weight, age, activity and health, so an estimate made a year ago may no longer fit.
Who should be careful with calorie targets
Counting calories and aiming at specific numbers is not right for everyone. People who are pregnant or breastfeeding, children and teenagers, people with diabetes, kidney or heart conditions, and anyone with a history of disordered eating should get individual advice. If thinking about food numbers causes distress, speak to a doctor or a registered dietitian. This calculator will always show an estimate, but it can never judge whether using it is a good idea for you.
Frequently asked questions
What is the difference between BMR, TDEE and maintenance calories?
BMR is the energy used at rest. TDEE adds the energy used for digestion, exercise and everyday movement. Maintenance calories is the everyday name for TDEE: the intake associated with a stable weight.
How accurate is a TDEE calculator?
It is an estimate. Studies of predictive equations show that individual errors of several hundred calories per day are common, so the result is best used as a starting point that you check against your own weight trend.
Which formula should I use?
Mifflin-St Jeor is a common default for healthy adults. Revised Harris-Benedict is an older alternative that often gives slightly different numbers. Katch-McArdle is useful only if you have a trustworthy body-fat measurement.
How many calories should I eat a day?
There is no single answer. Your maintenance estimate is a reference point, and what is right for you depends on your health, goals, medicines and life stage. A doctor or dietitian can advise on an amount that suits you.
Is it safe to eat below my maintenance calories?
This page does not say that any amount is safe. People differ, and some situations call for medical supervision. If you are considering a large or long-lasting reduction, talk to a healthcare professional first.
Why does the calculator show kilojoules as well as calories?
Many countries label food in kilojoules. One kilocalorie equals 4.184 kilojoules, so 2,039 kcal is 8,529 kJ.
Sources and limits of this page
Formulas: Mifflin MD and colleagues, American Journal of Clinical Nutrition 1990; Roza AM and Shizgal HM, American Journal of Clinical Nutrition 1984 (revised Harris-Benedict); the Katch-McArdle lean-mass equation; and activity multipliers as commonly used in practice. The Dietary Guidelines for Americans publish estimated calorie ranges by age, sex and activity level for general reference. This page is educational information, not medical advice.