How to Calculate Your TDEE (Total Daily Energy Expenditure)

How do you calculate your TDEE? Calculate your BMR (basal metabolic rate) with the Mifflin-St Jeor equation, then multiply it by an activity factor between 1.2 and 1.9 depending on how active you are day to day. The result, your total daily energy expenditure, is the number of calories your body burns in an average day, and it is the starting point for setting almost any nutrition goal.

TDEE calculators are everywhere, but most people never see the math behind the number they get. Here is how it actually works, and how accurate you should expect it to be.

What is TDEE?

TDEE stands for total daily energy expenditure, the total number of calories your body burns over 24 hours. That includes your basal metabolic rate (the calories you burn just staying alive), digesting food, and all the movement you do, from formal exercise down to fidgeting and walking to the kitchen.

It is the single most useful number in nutrition planning, because every calorie goal starts from it. Eating at your TDEE maintains your weight, eating below it drives fat loss, and eating above it drives weight and muscle gain.

How do you calculate BMR first?

Use the Mifflin-St Jeor equation, which research from the American Council on Exercise has found to be the most reliable of the common predictive formulas, generally landing within about 10 percent of measured resting energy expenditure for most adults.

The formulas are:

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

This gives you the calories your body burns at complete rest, before any activity is added on top.

What activity multiplier should you use?

Multiply your BMR by a factor that matches your real activity level, not your goals or your best week:

• 1.2: Sedentary, little to no exercise, a desk job
• 1.375: Lightly active, light exercise 1 to 3 days a week
• 1.55: Moderately active, moderate exercise 3 to 5 days a week
• 1.725: Very active, hard exercise 6 to 7 days a week
• 1.9: Extremely active, hard daily training plus a physically demanding job

BMR × activity multiplier = your estimated TDEE. From there, setting your calorie target for fat loss or a surplus for building muscle is just subtracting or adding from that baseline, and it also feeds directly into calculating your macros.

How accurate is a TDEE calculator, really?

Accurate enough to use as a starting point, not accurate enough to treat as gospel. Formula-based estimates are typically within about 10 percent of your true TDEE for most people, but real-world tracking data shows that for a meaningful share of people, the estimate can miss by 250 calories a day or more in either direction. Very lean athletes, older adults, and people with thyroid conditions tend to see the biggest gaps between the formula and reality.

That is not a reason to skip the calculation, it just means the number is a hypothesis, not a fact. Use it to set a starting calorie target, then let two to three weeks of real results tell you whether your true TDEE runs higher or lower than the formula guessed.

How do you find your real TDEE after the formula?

Track your calories and your weight trend for two to three weeks while eating at your calculated maintenance number. If your weight stays roughly flat, the formula was close. If you steadily gain or lose without meaning to, your real TDEE is higher or lower than the estimate, and you adjust your target from there rather than recalculating from scratch.

This is where most people's numbers fall apart in practice, not because the math is wrong, but because logging calories accurately for weeks in a row is tedious. It is exactly the gap Ori is built to close: OneFit's meal scanning estimates the calories and protein in a plate from a photo, so the tracking behind your TDEE check is quick enough to actually keep up.

Let OneFit AI build the plan for you

OneFit AI generates a personalized plan from your goals, picks the exercises, and adjusts as you get stronger. Free to download.

FAQ

How do you calculate your TDEE? First calculate your BMR (basal metabolic rate) using the Mifflin-St Jeor equation, then multiply it by an activity factor between 1.2 (sedentary) and 1.9 (very active). The result is your TDEE, an estimate of the total calories you burn in a day.

What is the difference between BMR and TDEE? BMR is the calories your body burns at complete rest just to stay alive, like breathing and keeping your heart beating. TDEE adds everything else on top of that: walking, exercise, digestion, and daily movement. TDEE is always higher than BMR.

How accurate is a TDEE calculator? Reasonably accurate as a starting point, typically within about 10 percent of your true number if you are honest about your activity level. But real-world data shows formula estimates can miss by 250 calories a day or more for many people, so treat it as a starting estimate you adjust from, not a fixed number.

What activity multiplier should I use for TDEE? Use 1.2 if you have a desk job and rarely exercise, 1.375 for light exercise 1 to 3 days a week, 1.55 for moderate exercise 3 to 5 days a week, 1.725 for hard exercise 6 to 7 days a week, and 1.9 only if you have a physically demanding job on top of hard training. Most people overestimate their activity level, so when in doubt, pick the lower option.

Should I eat at my TDEE, above it, or below it? Eat at your TDEE to maintain your current weight, below it to lose fat, and above it to build muscle. A deficit of 300 to 750 calories a day below TDEE is a sensible range for fat loss; a surplus of 200 to 300 calories a day works well for building muscle without adding much fat.