One number, three layers

TDEE — total daily energy expenditure — is the number of calories your body burns in a normal day. Everything in calorie tracking hangs off it: eat below TDEE and you lose weight, at it and you maintain, above it and you gain.

Nobody measures TDEE directly outside a metabolic lab. Apps estimate it in three layers: a base burn (BMR), an activity multiplier, and a goal adjustment. Here’s each layer without the jargon, using the exact formulas Calsheet’s goal wizard runs.

Layer 1 — BMR: what you burn by existing

Basal metabolic rate is what your body spends lying still: breathing, circulation, keeping 37°C, running a brain. It’s the biggest slice of your burn — usually 60–70% of the total.

The standard estimate is the Mifflin-St Jeor formula (1990), which most research and most trackers use because it’s about as accurate as a formula gets without lab equipment:

BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5   (men)
BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161 (women)

Worked example — a 34-year-old woman, 165 cm, 68 kg:

10×68 + 6.25×165 − 5×34 − 161 = 680 + 1031 − 170 − 161 ≈ 1380 kcal

That’s her floor: 1,380 kcal a day before she takes a single step.

Layer 2 — Activity: the honest multiplier

BMR gets multiplied by an activity factor:

Level	Factor	Roughly means
Sedentary	1.2	Desk job, little deliberate exercise
Lightly active	1.375	Walks, 1–3 light workouts a week
Moderately active	1.55	3–5 workouts a week
Active	1.725	Hard training 6–7 days a week
Very active	1.9	Physical job plus training

This is where most estimates go wrong, and almost always in the same direction: people overrate their activity. Two gym visits and a desk job is “lightly active,” not “moderately.” If you’re torn between two levels, pick the lower one — an overestimated TDEE gives you a budget you’ll silently overeat against, and then the scale contradicts the app.

Our example, lightly active: 1380 × 1.375 ≈ 1,898 kcal. That’s her TDEE — eat that daily and her weight roughly holds.

Layer 3 — The goal: why 15%, not 25

To lose weight you eat below TDEE. The tempting move is a huge cut; the sustainable one is modest. Calsheet applies −15% for weight loss and +10% for gaining, and the 15% is a deliberate choice:

It’s large enough to matter. For our example it’s ~285 kcal/day, about 2,000 kcal a week — roughly a kilogram of fat per month. Quiet, steady, real.
It’s small enough to live with. A 285-kcal cut is a snack and a smaller portion, not a rewrite of your diet. Hunger stays manageable, workouts keep their fuel, and — this matters most — you can keep it up for the months the job actually takes.

Heroic deficits (25–40%) produce fast first weeks and then muscle loss, constant hunger, and the quit. If the diary dies in week three, the deficit’s size never mattered. There’s more on that failure mode in why calorie counting fails.

Our example lands at 1898 × 0.85 ≈ 1,610 kcal/day — her daily budget.

The macro split

A calorie budget alone doesn’t say what to eat. Calsheet splits it 30/30/40 — protein/fat/carbs — by calories, then converts to grams (protein and carbs hold 4 kcal per gram, fat 9):

1610 × 0.30 / 4 ≈ 121 g protein
1610 × 0.30 / 9 ≈  54 g fat
1610 × 0.40 / 4 ≈ 161 g carbs

That’s a middle-of-the-road split: enough protein to protect muscle in a deficit (~1.8 g/kg for our example), enough fat for hormones, the rest to carbs. It is not the only defensible split — lifters often eat to a higher protein number and simply track it against the 7- and 30-day averages in Stats. In Calsheet the calorie budget itself is editable in Settings; the three macro targets are derived from it.

It’s an estimate. Treat it like one.

Formulas predict the average person with your stats; you are not the average person. Real TDEEs scatter around the estimate by ±10% or more — metabolism, fidgeting, and measurement error all play in.

So don’t audit the formula; audit the outcome:

Take the wizard’s number and eat to it, logged honestly, for two or three weeks.
Watch the weight trend — weekly averages, not daily readings, which bounce with water and salt. Calsheet’s weight journal and 30-day stats exist for exactly this comparison.
Losing much faster than ~0.25–0.5 kg a week? Raise the budget a bit. Not moving at all? Lower it by 100–150 kcal and give it another two weeks.

The formula gets you a good first guess in thirty seconds. The scale, given a few honest weeks, gets you your actual number. Between the two, you’ll know your TDEE better than any calculator on the internet — because yours is measured.