TDEE Calculator - Total Daily Energy Expenditure

What is TDEE?

Your Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns each day through basic biological functions, movement, exercise, and the energy cost of digesting food. It is your true maintenance level: eat at your TDEE and your weight stays stable; eat below it and you lose fat; eat above it and you gain mass.

TDEE is built on your Basal Metabolic Rate (BMR), the energy your body needs to sustain basic functions at complete rest. BMR typically accounts for 60-75% of TDEE. The remainder comes from the thermic effect of food (roughly 10%) and physical activity, which varies substantially between individuals.

How We Calculate Your TDEE

This calculator uses two validated equations to estimate BMR, then multiplies by an activity factor to produce TDEE.

Mifflin-St Jeor (primary): Published in 1990 (PMID 2305711), this equation was derived from a direct measurement study using indirect calorimetry. A 2005 systematic review by Frankenfield et al. (PMID 15883556) confirmed it as the most accurate predictive equation for resting energy expenditure in both normal-weight and obese adults.

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

Harris-Benedict (secondary): The revised Harris-Benedict equation (Roza and Shizgal, 1984; PMID 7369169) is shown alongside Mifflin as a comparison point. It tends to slightly overestimate BMR, particularly in overweight individuals.

Activity multiplier: BMR is multiplied by a Physical Activity Level factor from 1.2 (sedentary) to 1.9 (very active).

Activity Level Guide

Choosing the right activity multiplier has more impact on your result than the formula itself. Overestimating activity is the most common error in TDEE calculations.

• Sedentary (x1.2): Office-based work with no structured exercise.
• Lightly Active (x1.375): 1-3 days per week of genuine exercise.
• Moderately Active (x1.55): 3-5 days per week of moderate exercise.
• Active (x1.725): 6-7 days per week of hard training.
• Very Active (x1.9): Hard physical labour daily, or twice-daily training.

If in doubt, choose one level lower than you think and adjust after 2-3 weeks of real-world tracking.

TDEE and Your Goals

Once you have your TDEE, your calorie target follows directly from your goal.

Fat loss: A deficit of 500 kcal/day produces approximately 0.5 kg of fat loss per week. A 250 kcal deficit produces roughly half that rate and is easier to sustain long-term.

Maintenance: Eating at TDEE supports stable body weight and adequate energy for training recovery. Maintenance phases allow hormonal and metabolic markers to normalise after extended cuts.

Muscle gain: A surplus of 250-500 kcal/day provides the energy margin required for muscle growth without excessive fat gain. Natural trainees gain muscle slowly, so large surpluses accumulate primarily as fat.

Frequently asked questions

How accurate is my TDEE estimate?

TDEE formulas estimate your energy needs from weight, height, age, sex, and activity level but cannot account for all individual metabolic variation. Research shows these equations are accurate to within 10-15% for most adults. Treat your result as a starting point and refine it by tracking intake and body weight for 2-3 weeks.

Should I eat my TDEE every day?

Not necessarily. What matters is your average intake across the week. A single high-calorie day does not derail progress if the weekly total aligns with your goal. Monitor your weekly average and adjust based on 2-week weight trends rather than reacting to day-to-day fluctuations.

Why does Mifflin-St Jeor differ from Harris-Benedict?

Both equations estimate BMR from the same inputs but use different regression coefficients derived from different datasets. Mifflin-St Jeor (1990) used a larger sample with indirect calorimetry as the reference method. The 2005 Frankenfield review found Mifflin predicted measured REE within 10% for 82% of subjects versus 67% for Harris-Benedict. The difference is typically 50-200 kcal/day.

Sources

1. Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition. PMID 2305711 DOI
2. Roza AM, Shizgal HM (1984). The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. American Journal of Clinical Nutrition. PMID 7369169 DOI
3. Frankenfield DC, Roth-Yousey L, Compher C (2005). Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults. Journal of the American Dietetic Association. PMID 15883556 DOI