TDEE Calculator — Total Daily Energy Expenditure

What Is TDEE?

Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns in a 24-hour period. It includes your basal metabolic rate (BMR) — the energy required to keep you alive at rest — plus the calories burned through physical activity, digestion (thermic effect of food), and non-exercise activity thermogenesis (NEAT).

Your TDEE is the single most important number for any body composition goal. Eat below it and you lose weight. Eat above it and you gain weight. Match it and you maintain.

How Is TDEE Calculated?

Every TDEE calculator works in two steps: first estimate your BMR, then multiply by an activity factor. This calculator uses three validated BMR equations:

• Mifflin-St Jeor (1990): The gold standard. A 2005 review by the American Dietetic Association found it the most accurate equation for estimating BMR in both normal-weight and obese individuals.
• Harris-Benedict Revised (1984): The classic formula, revised by Roza and Shizgal. Slightly less accurate than Mifflin-St Jeor on average but still widely used in clinical settings.
• Katch-McArdle: Uses lean body mass instead of total weight. The most accurate formula for lean, athletic individuals — but requires knowing your body fat percentage.

BMR is then multiplied by an activity factor (1.2 to 1.9) to estimate total daily expenditure. The primary result uses Mifflin-St Jeor. All three formulas are shown for comparison.

TDEE for Lifters: Cutting vs Bulking

For strength athletes, the key is getting the deficit or surplus right. Research consistently shows:

• Cutting: A deficit of 300-500 kcal/day preserves the most muscle mass. A 2011 study by Garthe et al. found that athletes losing 0.7% bodyweight per week retained significantly more muscle than those losing 1.4% per week. Pair your deficit with high protein (1.8-2.2 g/kg) and continued heavy training.
• Bulking: A surplus of 250-500 kcal/day is sufficient to maximize muscle protein synthesis without excessive fat gain. Research by Slater et al. (2019) found that larger surpluses don't accelerate muscle growth — they just increase fat storage.
• Maintenance: Eating at TDEE is appropriate during recomposition phases, deloads, or when transitioning between cut and bulk phases.

Why Activity Level Matters More Than You Think

The difference between "sedentary" (1.2x) and "very active" (1.725x) for someone with a 1,800 kcal BMR is 945 calories per day. That's the difference between cutting and bulking without changing a single thing you eat.

Most people overestimate their activity level. Unless you have a physically demanding job and train 6-7 days per week, "moderately active" is likely your ceiling. A desk job with 4 training sessions per week is "lightly active" to "moderately active" — not "very active."

When in doubt, pick one level lower than you think. It's easier to add 200 calories than to undo a month of overeating.

How Accurate Are TDEE Calculators?

Honest answer: moderately accurate. A 2005 analysis found that Mifflin-St Jeor predicted BMR within 10% for about 82% of subjects. When you add the activity multiplier — which is an educated guess — total error can be ±300-350 kcal/day for most people.

That's why every experienced coach says the same thing: use the calculator as a starting point, then track your weight and intake for 2-4 weeks and adjust. If you're losing weight faster than expected, eat more. If weight is stalled, eat less.

RepStack tracks your bodyweight over time. When paired with your training data, it detects whether your current intake is supporting your goals — and adjusts recommendations automatically.

Tips for Best Results

• Weigh yourself at the same time each day (morning, after bathroom) and use a 7-day average.
• Don't adjust calories based on a single weigh-in. Weight fluctuates 2-4 lbs daily from water, food, and sodium.
• If you know your body fat percentage, enter it — the Katch-McArdle formula is more accurate for athletes.
• Recalculate every 4-6 weeks as your weight changes.
• Use this TDEE as input for the Macro Calculator to get your protein, carb, and fat targets.