TDEE calculator

How this TDEE calculator works

Total Daily Energy Expenditure is everything you burn in 24 hours: the energy keeping you alive at rest, plus digestion, plus every step, fidget and workout on top. This calculator builds it in two steps, the same way most reputable calculators do.

Step one estimates your basal metabolic rate (BMR) with the Mifflin-St Jeor equation, published in 1990 and still the most accurate of the common prediction equations for healthy adults. It takes weight in kilograms, height in centimetres and age in years:

Men: (10 × weight) + (6.25 × height) − (5 × age) + 5. Women: (10 × weight) + (6.25 × height) − (5 × age) − 161.

Step two multiplies that BMR by an activity factor to account for everything you do that is not lying still. The multipliers below are the conventional set used across the field.

• Sedentary (×1.2) — desk job, little deliberate exercise, under about 5,000 steps a day.
• Lightly active (×1.375) — light exercise 1–3 days a week, or a job with some walking.
• Moderately active (×1.55) — moderate exercise 3–5 days a week. Most consistent gym-goers land here, not higher.
• Very active (×1.725) — hard exercise 6–7 days a week, or a physically demanding job.
• Extra active (×1.9) — twice-daily training or heavy manual labour. Genuinely rare; almost nobody reading this belongs here.

A worked example

Take a 34-year-old woman, 168 cm, 70 kg, who lifts three times a week and otherwise sits at a desk.

BMR = (10 × 70) + (6.25 × 168) − (5 × 34) − 161 = 700 + 1,050 − 170 − 161 = 1,419 calories a day.

Applying the moderately active multiplier: 1,419 × 1.55 ≈ 2,200 calories a day. That is her TDEE estimate — the intake at which her weight should, on average, hold steady.

If she wanted a gentle deficit, she would eat 10–20% below that: roughly 1,760–1,980 calories a day. Not 1,200. The number people pick out of the air is almost always far lower than the number the arithmetic supports.

How accurate is a TDEE estimate, honestly?

Mifflin-St Jeor predicts measured resting energy expenditure within 10% more often than any other common equation — which also means it is outside 10% a meaningful share of the time. For a 2,200-calorie TDEE, a 10% miss is 220 calories in either direction.

The activity multiplier is the bigger source of error. It compresses an enormously variable thing — how much you actually move, how much you fidget, how hard those three gym sessions really are — into one of five numbers. Two people with identical BMRs and identical self-reported activity can differ by several hundred calories a day.

This is not a reason to skip the calculator. It is a reason to treat the output as a hypothesis to test, not a prescription to obey.

How to turn the estimate into your real number

Your own weight data beats any equation, and it takes about three weeks to collect.

• Eat at the estimated TDEE for 14–21 days, logging honestly — including the oil in the pan and the handful of nuts.
• Weigh yourself daily under the same conditions and watch the 7-day average, never a single day. Day-to-day swings are water, food volume and hormones, not fat.
• Compare the average of week one with the average of week three. Stable weight means the estimate was close.
• If you gained roughly half a kilo (about a pound) over that stretch, your true maintenance is around 250 calories lower than the estimate. Lost about the same, and it is around 250 higher.
• Adjust once, then hold for another two weeks. Chasing the number weekly makes noise look like signal.

Common mistakes with TDEE numbers

Most of the frustration with calorie targets traces back to a handful of predictable errors.

• Overstating activity. The single most common error, and it inflates your target by hundreds of calories. When in doubt, pick the lower multiplier.
• Double-counting exercise. The multiplier already includes your training. Adding a fitness tracker’s "calories burned" on top counts the same workout twice.
• Recalculating obsessively. Your TDEE does not change meaningfully week to week. Recalculate after 5 kg of weight change, not after a heavy weekend.
• Treating it as a floor to be beaten. A larger deficit is not a better one — it is a harder one to sustain, and adherence is what determines the outcome.
• Forgetting it falls as you lose weight. A smaller body burns less. Expect to recalculate every 5 kg or so.

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