How to Calculate Your Maintenance Calories (TDEE)

Your maintenance calories, often called TDEE (total daily energy expenditure), are the number of calories you'd need each day to keep your body weight roughly stable. To estimate it, calculate your basal metabolic rate (BMR) with the Mifflin-St Jeor equation, multiply it by an activity factor between 1.2 and 1.9, and then treat the result as a starting point. Your actual weight trend over the next two to three weeks will tell you how close the estimate is.

If you'd rather skip the arithmetic, the calorie calculator does the same math. Doing it once by hand is still worth it, because you'll understand what each part of the number means and why it can be off.

What TDEE is made of

A calorie is a unit of energy. Everything your body does, from keeping your heart beating to carrying groceries up the stairs, uses some of it. Your TDEE is the total of all that use over a day, and it comes from a few broad sources:

• Resting metabolism (BMR or RMR): the energy needed to keep you alive at rest, including breathing, circulation, and organ function. For most people this is the biggest piece. BMR stands for basal metabolic rate and RMR for resting metabolic rate; they're measured slightly differently but describe the same idea.
• The thermic effect of food: the energy used to digest and process what you eat.
• Exercise: planned workouts, runs, classes, and so on.
• Non-exercise activity: walking around, standing, fidgeting, chores, and everything else you do while awake.

Equations can't measure any of these directly. They estimate resting metabolism from your size, age, and sex, and then an activity factor covers the rest in one broad step.

Step 1: Estimate your BMR with Mifflin-St Jeor

The Mifflin-St Jeor equation was published in 1990 and is widely used by dietitians. A 2005 systematic review by Frankenfield and colleagues found it was the most reliable of the common prediction equations for healthy adults, although no equation is accurate for everyone.

Use weight in kilograms, height in centimeters, and age in years:

• Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
• Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161

To convert, divide pounds by 2.2046 to get kilograms, and multiply inches by 2.54 to get centimeters.

Each part of the formula reflects something real. Heavier and taller bodies have more tissue to keep running, so weight and height push the number up. Resting needs tend to drift down with age, so age is subtracted. The final constant differs by sex because, on average, men carry more muscle at the same size.

Step 2: Pick an activity factor

Next, multiply your BMR by the factor that best describes a typical week. These multipliers are the standard ones used alongside BMR equations. They're rough categories, so pick the one that fits most of your weeks rather than your best week.

• Sedentary (1.2): a desk job with little or no planned exercise.
• Lightly active (1.375): light exercise or sports 1–3 days a week.
• Moderately active (1.55): moderate exercise 3–5 days a week.
• Very active (1.725): hard exercise 6–7 days a week.
• Extra active (1.9): hard daily training plus a physical job, or training twice a day.

Most people overestimate their activity level. If you're stuck between two categories, start with the lower one. Three 45-minute gym sessions a week alongside a desk job usually fit "lightly active" better than "moderately active." The reason is that a workout, even a hard one, is a small part of a 24-hour day. The hours you spend sitting or moving around outside the gym often matter just as much.

Step 3: A worked example

Here's the math for a 35-year-old woman who is 165 cm (about 5'5") tall, weighs 68 kg (about 150 lb), and does moderate exercise four days a week.

1. 10 × weight: 10 × 68 = 680
2. 6.25 × height: 6.25 × 165 = 1,031.25
3. 5 × age: 5 × 35 = 175
4. BMR: 680 + 1,031.25 − 175 − 161 = about 1,375 calories per day
5. TDEE: 1,375 × 1.55 = about 2,130 calories per day

For comparison, a 30-year-old man who is 180 cm tall, weighs 80 kg, and is lightly active gets:

• BMR = 800 + 1,125 − 150 + 5 = 1,780
• TDEE = 1,780 × 1.375 = about 2,450 calories per day

Round your result to the nearest 50 or so. Writing 2,131.6 implies a precision the equation doesn't have.

Why the result is only an estimate

The equation's average error for a group is small, but any one person's measured resting metabolism can differ from the prediction by about 10% or more. For the woman in the example, that's a realistic range of roughly 1,900 to 2,350 calories, and that's before you add the uncertainty in the activity factor.

Some reasons your real number may differ:

• Body composition. The equation uses total weight, so it can't tell muscle from fat. Two people with the same weight and height can burn different amounts at rest.
• Daily movement. Non-exercise activity varies a lot between people and can change when you eat less or more.
• Tracking error. Food labels and portion estimates are approximate, so the intake you log won't exactly match what you eat.
• Health and life stage. Some medical conditions, medications, pregnancy, and breastfeeding change energy needs. The equation doesn't account for them.

This is why the next step matters more than the formula itself. The formula gives you a sensible first guess, and your own results tell you how to correct it.

Step 4: Check the estimate against your weight trend

Your scale weight goes up and down from day to day because of water, salt, carbohydrate intake, digestion, and (for many women) the menstrual cycle. A single weigh-in tells you very little. An average over a week tells you a lot more, because those random ups and downs tend to cancel each other out.

Here's a simple way to test your estimate:

1. Eat close to your estimated TDEE every day for two to three weeks. You don't have to hit it exactly; aim to stay within about 100 calories on most days.
2. Weigh yourself at least three or four mornings a week, after using the bathroom and before eating or drinking, in similar clothing.
3. Average each week's weigh-ins.
4. Compare the weekly averages and read the trend:
   • Stable (within about half a pound, or 0.2 kg): your estimate is close to your real maintenance.
   • Rising steadily: your maintenance is probably lower than the estimate. Reduce your daily target by about 100–200 calories and check again for two weeks.
   • Falling steadily: your maintenance is probably higher. Add about 100–200 calories and check again.
5. Keep your activity roughly the same during the test. If you add a new training program halfway through, the numbers get harder to read.

A common rule of thumb says a pound of body fat is about 3,500 calories. Research by Kevin Hall and colleagues showed that this rule oversimplifies how weight changes over time, so treat it as a rough guide for short-term adjustments only. Small, regular corrections based on your trend work better than one big recalculation.

Using your maintenance number

Once you have a maintenance number you trust, you can use it to set a goal.

To maintain: eat around that number and keep checking your weekly average every month or so. Recalculate if your weight, training, or job changes a lot.

To lose fat gradually: a modest deficit, often around 10–20% below maintenance, is a common starting point. A deficit simply means eating somewhat less than you burn. For the woman in the example, that's roughly 1,700–1,900 calories a day. Smaller deficits are easier to keep up and make it easier to keep training well. The CDC notes that people who lose weight gradually are more likely to keep it off.

To support muscle gain: if you're lifting weights and want to build muscle, a small surplus of about 5–10% above maintenance is usually enough. Bigger surpluses mostly add more fat, not more muscle. Getting enough protein matters too; see how much protein you need per day.

Whatever the goal, pair your nutrition with regular activity. The weekly exercise guidelines are a sensible baseline, and a beginner strength training plan helps you keep muscle when you eat in a deficit.

When to get professional advice

Calorie math is a planning tool, not medical advice. Talk to a doctor or registered dietitian before changing how you eat if you:

• Are pregnant, breastfeeding, or under 18
• Have diabetes, kidney disease, heart disease, or another chronic condition
• Take medication that affects appetite, blood sugar, or weight
• Have a history of disordered eating, or notice that tracking makes you anxious or obsessive
• Are thinking about eating far below your estimated needs

Very low calorie diets should only be done with medical supervision. If you feel dizzy, unusually tired, or unwell while eating less, raise your intake and talk to a health professional.

Sources

• Mifflin and St Jeor, equation for resting energy expenditure (1990)
• Dietary Guidelines for Americans 2020–2025