Formula, in Fat Loss

TDEE Formula

Total Daily Energy Expenditure is BMR multiplied by an activity factor. The factor is the imprecise part — even within a tier, two people can spend 400+ calories apart in non-exercise activity thermogenesis.

3 variables. Published Mar 12, 2026. Updated May 10, 2026. By AI Fit Hub.

Education, not medical advice. The result comes only from the published formula and your inputs. How we check our formulas.

Formula

TDEE = BMR × activity_factor

Variables

TDEE

Total Daily Energy Expenditure

Calories burned per 24 h including exercise, fidgeting (NEAT), and the thermic effect of food.

BMR

Basal Metabolic Rate

From Mifflin-St Jeor or an equivalent equation. Roughly 60–75% of TDEE in sedentary adults.

activity_factor

Activity multiplier

1.2 sedentary (desk job, no exercise); 1.375 light (1–3 workouts/week); 1.55 moderate (3–5/week); 1.725 very active (6–7/week or physical job); 1.9 athlete (twice-daily sessions).

Step by step

1

Calculate BMR using Mifflin-St Jeor.

30-year-old male, 78 kg, 178 cm → BMR 1,747.5.
2

Pick the activity factor that matches the average week, not the peak week.

Lifts 4×/week, walks daily → moderate (1.55).
3

Multiply BMR by the factor.

1,747.5 × 1.55 = 2,708.6 cal/day.
4

Treat the result as a starting point. Track weight for 2–3 weeks; if it doesn't move at maintenance, adjust the factor up or down by 0.1.

If weight drifts up 0.5 kg/week at 'maintenance', actual factor is closer to 1.45 — drop 250 calories.

Worked example

30-year-old male, 78 kg, 178 cm, lifts 4×/week

BMR

1,747.5

Activity factor

1.55 (moderate)

TDEE = 1,747.5 × 1.55 = 2,708.6 calories/day

Maintenance ~2,710 cal/day. Subtract 500 for a 1 lb/week deficit, add 250 for a lean-gain surplus.

Common variations

Direct measurement via doubly-labeled water is the gold standard but costs ~$3,000 and takes 2 weeks.

Wearable estimates (heart rate × movement) systematically overestimate by 15–30% — useful for trend, not absolute number.

For very-low-BMI or very-high-BMI bodies, swap Mifflin-St Jeor for Katch-McArdle once you have a body-fat estimate.

Run the numbers next

Nutrition BMR Calculator
Estimate basal metabolic rate and maintenance calories using Mifflin-St Jeor assumptions.
Planning Calorie Deficit Calculator
Estimate required daily calorie deficit for a target timeline and bodyweight change.

Sources

Measuring energy expenditure in clinical populations: rewards and challenges , European Journal of Clinical Nutrition (2013) — Psota & Chen
Accuracy in Wrist-Worn, Sensor-Based Measurements of Heart Rate and Energy Expenditure in a Diverse Cohort , Journal of Personalized Medicine (2017) — Shcherbina et al.