How to calculate TDEE correctly (and why most online calculators are off by 10%)

Total Daily Energy Expenditure (TDEE) is the calorie number every diet and bulk plan revolves around. The formula has two parts — basal metabolic rate (BMR) and an activity multiplier — and the second one is where most calculators lose accuracy.

The formula

TDEE = BMR × activity_factor

BMR is what your body burns at complete rest. The most accurate predictive formula is Mifflin-St Jeor (1990):

Male: BMR = 10·weight(kg) + 6.25·height(cm) − 5·age + 5
Female: BMR = 10·weight(kg) + 6.25·height(cm) − 5·age − 161

Plug your numbers into our BMR calculator for the BMR value, then multiply by the activity factor below.

The activity factor (where most calculators go wrong)

Standard multipliers:

• 1.2 — Sedentary. Desk job, no exercise. Genuinely sitting most of the day.
• 1.375 — Lightly active. Light exercise 1-3 days per week, or a job with some walking.
• 1.55 — Moderately active. Moderate exercise 3-5 days per week.
• 1.725 — Very active. Hard exercise 6-7 days per week.
• 1.9 — Extremely active. Physical job (construction, professional athlete) plus daily training.

Three common ways people get this wrong:

1. Overestimating activity

Most people walking past a fitness app classify themselves one tier higher than they should. A desk worker who lifts three times a week is “moderately active” — not “very active.” The 25% gap between consecutive tiers translates into hundreds of calories a day.

A sanity check: in a typical 24-hour day, if you spend more than 16 hours sitting or lying down (desk + sleep), your activity tier is at most “lightly active” regardless of what you do for an hour at the gym.

2. Counting one good week as the norm

The activity factor should reflect your typical week, averaged over a month. One hard week followed by three lazy weeks averages to sedentary, not moderately active. Be honest.

3. Ignoring NEAT

Non-exercise activity thermogenesis (NEAT) — fidgeting, standing, walking to the kitchen — varies dramatically between people. Some “sedentary” office workers burn 400 calories more per day than others, purely through unconscious movement. NEAT isn’t in the formula directly; it’s the main reason individuals deviate from their predicted TDEE by ±15%.

The 2-week feedback loop

Any calculator returns an estimate. Your actual TDEE is whatever number, when eaten daily, leaves your weight unchanged over two weeks. The protocol:

1. Get the estimated TDEE from any calculator.
2. Eat exactly that many calories daily for 14 days.
3. Weigh daily, same time, same conditions. Use the 14-day average.
4. If average weight is stable: estimated TDEE was correct.
5. If you gained weight: actual TDEE is lower than estimated. Subtract calories until you stabilise.
6. If you lost weight: actual TDEE is higher. Add calories.

After this calibration, the activity factor that matched your real outcome is your honest factor — use that one going forward, not the one your gym app picked.

When BMR estimates themselves are off

Mifflin-St Jeor predicts BMR within about ±10% for most adults. Where it’s less accurate:

• Highly muscular people. Predicts low. Muscle is more metabolically active than the formula assumes.
• Obese individuals. Predicts high. Adipose tissue burns fewer calories per kilogram than lean mass; Mifflin-St Jeor doesn’t distinguish.
• People with hyperthyroid or hypothyroid conditions. Thyroid drives basal metabolism by ±15-30%; the formula doesn’t know.

For most general-population users, Mifflin-St Jeor is the right starting point. The 2-week feedback loop catches the residual error.

What “maintenance calories” actually means

Your maintenance calorie level is the daily intake that produces zero net weight change over time. It’s synonymous with TDEE only if your body composition is stable. During a deliberate cut or bulk, daily intake is by definition different from maintenance — that’s the whole point.

Common targets relative to maintenance:

• Aggressive cut: maintenance − 25-30%.
• Moderate cut: maintenance − 15-20%.
• Lean bulk: maintenance + 10-15%.
• Recomp (build muscle while losing fat): maintenance ± 0-5%, depends on training stimulus and protein intake.

Get your maintenance number from our BMR & TDEE calculator, then verify it with the 2-week loop, then adjust from there.